European water treatment code
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Commission of the European Communities
Diteciotaie ■ Generai fot Science, Research ana Development
Environment Research Programme
ADVANCED DESIGN AND OPERATION
OF
MUNICIPAL WASTE WATER TREATMENT PLANTS
PILOT PLANT FLQW PI,
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: £ £ ; «! ; , ' £ ;
AERATION TANKS AND SE CONDARY SE TTLE R WE RE THE RMICALLY INSULATE D
FOR LOW TE MPE RATURE E XPE RIVE NTS
Contract N° EV4V0073E (A)
L. Concha
M. Henze
TECHNOLOGIES FOR E NVIRONME NTAL PROTE CTION
REPORT 1
EUR 15030 EN
JUNE 1992
COMMISSION OF THE EUROPEAN COMMUNITIES
Directorate-General for Science, Research and Development
Environment Research Programme
CONTRACT NO. EV4V-0073-E (A)
L. Concha
M. Henze
ADVANCED DESIGN AND OPERATION
OF MUNICIPAL WASTE WATER
TREATMENT PLANTS
Technologies for Environmental Protection
Report 1
PARL EUROP. Biblioih.
N . C . ^ Áio^o
CI.
EUR 15030 EN
JUNE 1992
Advanced Design and Operation of Municipal Waste Water Treatment Plants
Contract No. EV4V-0073-E(A)
Project coordinator: L. Concha
Ente Vasco de la Energia (EVE)
Edificio Albia 1
San Vincente. 8 - Pianta 14
48001 - Bilbao
Edited by: L. Concha, Ente Vasco de la Energia (EVE), Spain
M. Henze, Technical University Lyngby, Denmark
J. Busing, CEC, DG XII, D-l, Brussels, Belgium
ISBN 2-87263-085-6
Depot legal D 1992/0157/09
This is report No 1 in the Technologies for Environmental Protection Report Series
of the Environmental R&D Programme of the Commission of the European
Communities, Directorate-General for Science, Research and Development.
For more information concerning this series, please contact :
Mr. H. Ott
CEC-DG XII/D-1
Rue de la Loi, 200
B-1040 Brussels
No part of this publication may be reproduced, stored in a retrieval system, or
transmitted in any form or by any means, electronic, mechanical, photocopying,
recording or otherwise, without indicating the above mentioned references.
Publication No EUR 15030 EN of the
Commission of the European Communities,
Dissemination of Scientific and Technical Knowledge Unit,
Directorate-General Information Technologies and Industries,
and Telecommunications,
Luxembourg
© ECSC-EEC-EAEC, Brussels-Luxembourg, 1993.
LEGAL NOTICE
Neither the Commission of the European Communities nor any person acting on
behalf of the Commission is responsible for the use which might be made of the
following information.
E. GUYOT SA, rue Ransfort 25, 1080 Brussels
Printed in Belgium
- III -
FOREWORD
Research work desoribed in the report was aimed at optimizing
design and operation of unified Sludge Age Control Technology
(USCT) in order to enable aotivated sludge plants to treat a
greater variety and strength of municipal and industrial waste
waters than a conventionally designed and operated plant.
The conventional and the new processes were studied in parallel,
eaoh fed with about 85% domestic and 15% industrial waste water
originating from major industrial sources located in the
Galindo/Bilbao area.
The present report is the first issue of a series of Technologies
for Environmental Protection Reports supported under the EC
Environment Programme of DGXII.
J. Busing, DGXII/D-1
1-
CONTENTS
SUMMARY AND CONCLUSIONS
INTRODUCTION
5
7
PILOT PLANT DESCRIPTION
10
2.1. Pumping of domestic sewage
14
22. Primary settling
14
23. Biological reactor
15
2.4. Secondary settling
16
2.5. Sludge recirculation
17
2.6. Incoming industrial waste reception
18
2.7. Means for homogenization, preparation and dosage of industrial wastes.
18
METHODOLOGY
19
3.1. Research schedule
19
32. List of sampling points and general sampling strategy
20
33. List of analyzed parameters
24
3.4. List of continuously measured parameters
27
3.5. Total number of samples and analysis
29
3.6. Scientific and technical team
30
3.7. Analytical methods
31
OPERATING STRATEGY
33
4.1. Control parameter: sludge age.
34
42. Control parameter: F/M ratio
38
-2RESULTS
44
5.1. Operating conditions in intensive periods
46
52. Hydraulic data
47
53. Influent to Pilot plant
48
5.4. Metals in influent to pilot plant
49
5.5. Primary clarifiers effluents
50
5.6. Metals in primary clarifiers effluents
51
5.7. Final effluents
52
5.8. Metals in final effluents
53
5.9. Diurnal variations CONV system
54
5.10. Diurnal variations FMCT system
55
5.11. Activated sludge mass balance (1)
56
5.12. Activated sludge mass balance (2)
57
5.13. Sludge quality
58
5.14. Metals in primary sludge
59
5.15. Metals in activated sludge
60
5.16. Aeration parameters
61
5.17. Energy consumption
62
5.18. Sludge age calculation
63
MODELLING
64
6.1. Introduction
64
62. Concepts of models
64
6.2.1.
Activated sludge model
64
622.
Secondary clarifier model
66
63. CAB description
68
6.4. Model plant
69
6.5. Input data handling
70
-3-
7.
6.6. Operation conditions used for modelling
72
6.7. Modelling and analyzing
73
6.7.1.
Notes on modelling
73
6.12.
Some results from the modelling of the pilot plant
74
6.73.
Calibration of constants in the model
77
6.8. Conclusion
80
6.9. List of symbols
81
DISCUSSION OF RESULTS
7.1. Primary settling
83
7.2. Activated sludge process
86
7.2.1.
Nitrification
86
122.
Activated sludge quality
90
123.
Settling velocity
96
12.4.
Effluent quality
100
12.5.
Yield coefficient
106
7.2.6.
Energy consumption
110
13.
8.
83
Secondary settling
110
7.4. Heavy metals
118
7.5. General wastewater characteristics
119
CONCLUSIONS
120
8.1. General conclusions
120
82. New system
122
S3.
123
Modelling
9.
LIST OF SYMBOLS
124
10.
REFERENCES
126
ANNEXES
1.
Drawing and photographs of the Pilot plant and Laboratory
129
2.
Description of the analytical methods
139
-50.
SUMMARY AND CONCLUSIONS
Although there is a vast number of wastewater treatment plants operating throughout the
world, it is a well-known fact that many of them don't meet the standards they were
designed for, particularly in plants treating mixed wastewaters (domestic and industrial).
The problems usually affecting the plants are influenced by the following basic factors:
sludge acclimatisation capacity to industrial wastes, flexibility and controlability of the
process, secondary settling performance and aeration capacity.
Knowing these, it was the purpose of the research to investigate a new process called
FMCT process (FMCT: food mass control technology) that is a new modification of the
activated sludge system. FMCT system includes a big settling tank which allows for
storage of biomass and control of F/M-ratio under varying load conditions. The new
process was supposed to provide the following advantages over the conventional system:
Better adjustment of biomass to instantaneous needs.
Reduction of aeration tank volume using concentrations of 5-8 g MLSS/1.
Reduction of energy consumption in aeration tanks.
Better quality of treated wastewaters.
Lower volume of excess sludge.
Lower probability of bulking problems.
A pilot plant study has been carried out in Galindo (Spain) primary treatment full scale
plant, treating mixed wastewaters (domestic and industrial) in two parallel lines, one
working with the CONV system and the other with FMCT system.
- 6-
Seven intensive study periods were carried out covering a range of temperatures: 8" C
to 2? C, and F/M-ratios: 0.15-0.60 (kg BOD/kg VSS.day).
A new mathematical model based on the IAWPRC activated sludge model no. 1 was
developped for the new system giving special attention to model the secondary settler.
The effluent quality found in both systems is well below the proposed EEC standards.
The soluble inert COD in the effluent is approximately 30-40 mg/1. Increasing F/Mratio increases soluble COD in the effluent having decreasing temperature a similar
effect.
Nitrification rates were low due to low pH and low alkalinity. Calculated nitrification
rates with IAWPRC activated sludge model no. 1 for pH-(7-7.5) were normal so no
additional inhibitory effects on nitrification was detected.
The yield is highly influenced by temperatures and F/M-ratio. For similar F/M-ratio the
yield at ffC was approximately twice the yield at 23° C.
The new system has proved to allow for better adjustment of biomass to instantaneous
needs due to storage of large amounts of biomass in the big clarifier. Other advantages
observed were: less occurrence of bulking and foaming problems, excess sludge volume
lower due to higher concentrations reached in secondary settler and sludge produced was
more stabilized with lower percentage of volatile suspended solids.
The mathematical model has shown to be a valuable tool for interpretation of
experimental results and for description of the actual settler performance and the
performance of the biological reactors.
INTRODUCTION
Bilbao is a coastal city in northern Spain which has about 1,000,000 habitants in
its drainage area. Sizable industry discharges its wastewaters to a severely polluted
estuary as well.
The "Consorcio de Aguas de Bilbao, Abastecimiento y Saneamiento" (CAGB), is
a public company owned by 24 municipalities.
Now the sewerage scheme in Bilbao is being developed and the wastewater
treatment plant of Galindo is in operation providing primary treatment to about
150,000 p.e. since July 1990.
The next stage in the scheme will be the construction of the biological treatment
in Galindo wastewater treatment plant as well as the construction of new sewers.
For that purpose a pilot plant was built in 1981 in order to investigate the
performance of biological treatment with the Bilbao wastewater. During the
period 1981-1987 several investigations were conducted in the pilot plant; resulting
in great experience to a Consorcio team that becomes specialised in biological
wastewater treatment processes as well as analytical methods.
Although there is a vast number of wastewater treatment plants operating
throughout the world, it is a well-known fact that many of them don't meet the
standards they were designed for. The problems usually affecting these plants are
influenced by five basic factors:
- sludge acclimatization capacity to industrial wastes;
- flexibility of the process;
- controllability of the process;
- secondary settling;
- aeration capacity.
-8-
The effects of deficiencies in these five areas produce the typical problems such
as:
- sludge bulking and flotation;
- scum production;
- inhibition caused by toxic agents;
- high consumption of electricity;
- poor performance in the treatment
Knowing these, it was the purpose of the Consorcio to investigate new designs and
operational strategies for biological treatment of mixed (domestic and industrial)
wastewaters. The new process to investigate was called FMCT process (FMCT:
Food to Microorganisms Control Technology). FMCT system includes a large final
settling tank which allows storage of biomass and control of F/M ratio under
varying load conditions. The new process was supposed to provide the following
advantages over the conventional system:
1. Better adjustment of biomass to the instantaneous needs.
2. Reduction of aeration tank volume using concentrations of 5 to 8 g/1 of mixed
liquor suspended solids.
3. Reduction of energy consumption in aeration tanks.
4. Better quality of treated wastewaters.
5. Lower volume of excess sludge.
6. More stable sludge with a lower proportion of volatile suspended solids.
7. Better sedimentation characteristics of the sludge with lower probability of
bulking problems.
To investigate the new process the pilot plant was modified having two parallel
lines one working with the Conventional (CONV) system and the other with the
FMCT system. The pilot plant was provided with cooling systems to carry out
experiments at low temperatures (8°C).
-9The investigation project was presented in the DG XII by the Consorcio de Aguas
de Bilbao and EVE (Ente Vasco de la Energia). Prof. Mogens Henze from the
Technical University of Denmark was in charge of developing a mathematical
model for the new system giving special attention to model the secondary clarifier.
During the investigation Prof. Peter Grau from the Prague Institute of Chemical
Technology became involved in the project giving valuable advice in activated
sludge population dynamics.
The pilot plant was installed in the Galindo wastewater treatment plant were it
was fed with mixed wastewaters (domestic and industrial). The experiments have
being performed during two years and finished in March 1991.
-102.
PILOT PLANT DESCRIPTION
As described in the previous chapter the plant is equipped with two lines or
processes which can be used in parallel. One of the lines is the conventional
completely stirred activated sludge tank followed by a traditionally sized final
clarifier, so called CONVentional process (CONV), while the other system has
much larger final clarifier. The system is called "Food to Microorganisms ratio
Control Technology" (FMCT). A flow diagram of the pilot plant is shown in
Figure 2.1.
The sewage treatment lines consist of the following:
- pumping of domestic sewage;
- mixing, homogenization and distribution to the two lines of both domestic and
industrial sewage;
- primary settling;
- biological reactor for activated sludge;
- secondary settling;
- sludge recirculation.
For the sake of completeness and for industrial waste composition purposes, the
following is available:
- incoming industrial waste storage tanks;
- means for homogenization, preparation and dosage of industrial wastes.
A detailed drawing of the pilot plant is included in Annex 1.
of secondary settler
recirculation capacity
AERATION TANKS AND SECONDARY SETTLER WERE THEfîMICAU.Y INSULATED
FOB LOW TEMPERATURE EXPERIMENTS
■at^Mg'-'»- ::...; / ' f t B g a i a s g s B B —
t=MC'r^ 2 - limali
12-
Fig. 2.2. GENERAL VIEW OF PILOT PLANT
Fig. 2.3. INDUSTRIAL WASTES STORAGE TANKS
- 13-
Fig. 2.4. AERATION TANK CONTROL METERS
äöaa _ .
**•' '
:
: *
I •• • •
wrosi» i ¿TU!
Fig. 2.5. PILOT CONTROL ROOM
-142.1.
Pumping of domestic sewage
In a well two submersible pumps are placed, one as a spare pump, of the
displacement type and protected by a bar screen for solids, hand-operated but
designed for self-cleaning.
The flow rate of each pump is 15 m 3 /h, the impulse pipe is made of
polypropylene, 1,000 m in length and 2.1/2" in diameter
and flows into a
homogenization chamber where an agitator mixes domestic and industrial wastes
adequately. Distribution to each line takes place through two weirs. The flow rate
to each unit is controlled.
Pumping characteristics
2.2.
No. of pumps
2
Unit flow rate
3/
15 m h
Power
5.5 kW
Type of runner
Displacement
Impulse piping
2.1/2" dia. Polypropylene
Primary settling
Each sewage treatment line is equipped with a primary settler 2.2 m in diameter,
made of steel plates and protected with epoxy paint.
The sewage flows in through a pipe into a central distribution well; it flows out by
gravity through a V-notched weir.
The bottom- is conical shaped, without scrapers, and the sludge is removed by
means of an automatic, programmed pneumatic valve.
- 15-
Primary settling characteristics
2.3.
Design flow rate
3 m3/h each settler
Diameter
2.2 m
Overflow rate
0.79 m/h
Total volume
12 m3
Biological reactor
Each line is equipped with a 18 m3 tank, where biological reactions take place.
Supply of oxygen is made by means of two blowers (one for each line), which
inject air into the reactor through fine-bubble ceramic diffusers.
Cooling coils are inside the reactors in order to enable carrying out tests at
temperatures lower than ambient temperature. The reactors are, therefore,
thermally insulated.
To prevent solids from settling when the airflowis low, each reactor is fitted with
a submerged propeller.
In each reactor tank, the pH, dissolved oxygen and temperature are continuously
controlled, the last two parameters acting automatically on the supply of air and
on the refrigerating equipment.
- 16
Biological reactor characteristics
2.4.
Volume
18 m3
Material
Steel plates, protected by epoxy paint
Design retention time
6h
Air injection flow
125 m3/h each blower
Thermal insulation
Expanded polystyrene
Temperature reduction
Vaporization coils
Secondary settling
The conventional line is equipped with a secondary settler 2.2 m in diameter,
made of steel plates; the FMCT line has a 4 m diameter settler, also made of steel
plates.
In both settlers sewage flows in through a central baffle well and overflows
through a V-notched weir.
The bottom is of conical shape; the 4 meter diameter settler was equipped with
a bottom scraper.
For low-temperature operation both settlers are insulated by means of a layer of
expanded polystyrene.
- 17-
Secondary settler characteristics
Conventional Line FMCT Line
2.2
4
0.79
0239
kg/(m2.h)
4.14
535
Thermal insulation
Expanded polystyrene
Diameter m
Overflow rate
m/h
Aplied solids flux
Total volume
2.5.
m3
12 m3
405
Sludge recirculation
The CONV line is equipped with two Mono rype pumps, capable of a variable
flow rate by means of frequency converters operated from the central panel.
The FMCT line has three pumps with the same features, whereby the recirculating capacity is increased.
There exists a continuous control on the flow of sludge which is being recirculated, with a direct reading on the panel.
Sludge recirculation characteristics
Conventional Line
No. of pumps
2
FMCT Line
3
Unit flow rate
0.6-4 m3/h
l-6m 3 /h
Recirculation rate
0.7-3 m3/h
2-12 m3/h
Flow rate variation
Frequency converter
- 182.6.
Incoming industrial wastewater reception
There is a set of 5 m3 m cylindrical tanks, made of glass-fibre reinforced
polyester, for the reception of concentrated industrial wastewaters.
Each tank contains a vertical mixer driven by a slow-speed .motor for the
homogenization of wastes received by tank trucks at variable intervals.
Each tank is fitted with a bottom-discharging valve through which a part of
each type of waste is removed to the 20 m3 joint preparation tank.
2.7.
Homogenization. preparation and dosage of industrial wastes
There is a homogenization and preparation tank where the various types of
industrial wastes are brought together, mixed and diluted. After preparation,
the whole mixture is transferred into another storage tank, whence it is finally
dosed, by means of a variable flow pumping unit, into the general inlet trough
where it is mixed with domestic sewage.
Both the preparation thank and the industrial waste dosage tank have a 20 m3
capacity.
-193.
METHODOLOGY
In the course of the research work, seven intensive study periods were carried
out under different operating conditions of the pilot plant.
In Periods 1 and 2 temperatures were maintained in the 14°C region (Winter).
In Period 3 the temperature was about 20°C (Spring).
In Periods 4 and 5 the temperature was kept in the 23°C region (Summer).
Finally, in Periods 6 and 7 (Winter) the cooling systems installed in the
aeration tanks were used, the temperature being kept at about 8°C. Ambient
temperature during the latter periods was 10-12°C.
At each temperature two different conditions of F/M ratio were tested.
In between the various intensive periods there were transition periods in which
the pilot plant was stabilized to the specific operating conditions which were
subsequently maintained during the next intensive period.
3.1.
Research schedule
Period 1: 16-19 Jan. '90
Temperature approx. 13°C
CONV. Line
F/M = 0.376
FMCT Line
F/M = 0.275
Period 2: 26 Feb-26 Mar '90
Temperature approx. 16°C
CONV. Line
F/M = 0.405
FMCT Line
F/M = 0.174
-20
Period 3: 16-30 May. '90
F/M = 0.845
FMCT Line
F/M = 0.22
Period 4: 9-24 Jul '90
Temperature approx. 23°C
CONV. Line
F/M = 0205
FMCT Line
F/M = 0.162
Period 5: 20 Aug-3 Sep '90
Temperature approx. 23°C
CONV. Une
F/M = 0.4
FMCT Line
F/M = 0.282
Period 6: 14-31 Jan '91
Temperature approx. 8°C
CONV. Line
F/M = 0.231
FMCT Line
F/M = 0.207
Period 7: 18 Feb-8 Mar '91
3.2.
Temperature approx. 19.5°C
CONV. Line
Temperature approx. 8°C
CONV. y ne
F/M = 0.579
FMCT Line
F/M = 0.429
List of sampling points and general sampling strategy
For identification of the sampling points, the following codes have been used:
First character Identifies the treatment line.
C:
CONV
U:
FMCT
-21 Other characters: Identify the location of the sampling point.
TJWO: domestic sewage
IWO: industrial waste
SPO:
influent into plant - domestic and industrial mixture
SPI
effluent from primary settling
SP2;
contents of aeration tank
SP3
effluent from aeration tank
SP4:
effluent from secondary settling
SP5
re-circulated sludge from secondary settling
SP6:
sludge from mixed liquor
SP7:
sludge removed from primary settling
Sampling points scheme is shown in figure 3.1
Types of samples taken are as follows:
Type 1: composite - 24 hours (500 ml samples taken hourly)
Type 5: grab taken at 9:00 hrs
Type 6: grab taken at 17:00 hrs
Type 7: grab taken at 01:00 hrs
Both during the intensive and transition periods, the following samples were
taken on a daily basis:
1) SPO:
composite sample from 24 hrs, influent to pilot
plant.
2) CSP1 and USP1:
composite sample from 24 hrs, effluents from the
primary settling.
3) CSP4 and USP4:
composite sample from 24 hrs, final effluents.
4) CSP2 and USP2:
3 grab samples daily (9hrs, 17 hrs and 01 hrs),
mixed liquors.
FIG. 3.1: SAMPUNG POINTS
PILOT PLANT
LINE CONV
AER AVON
TANK
MIXING TANK
RECIRCULACtON
-»
—
EFFLUENT
WASTED
SP.)
...LINE FMCT
—
RECIRCULAVON
—
SLUDGE
EFFLUENT
WASTED
SLUDGE
IW2 1
INDUSTRIAL
PI
f IW3
WASTE
L^^_^
DOSING
INDUSTRIAL
TANK
WASTE
MIXING TANK FOR
INDUSTRIAL
WASTE
DOMESTIC WASTE
IW5 J
I IW6
-23-
5) CSP5 and USP5:
3 samples daily (9 hrs, 17 hrs and 01 hrs) of recirculated sludge.
At the end of each intensive period, additional samples were taken:
6) CSP7 and USP7:
Grab sample of primary sludge at 9 hrs.
Sampling was done manually, by the plant operators in all cases, except for
variability studies, when samples were taken by automatic samplers.
Upon completion of the last two intensive periods, a special sampling was
made to define the varying conditions in the pilot plant. This sampling was
carried out by taking samples every 2 hours for a 24 hours period, each
individual sample being independently analyzed.
The analyzed sampling points were as follows:
CSP1: effluent from primary settling, CONV line
USP1: effluent from primary settling, FCMT line
CSP4: effluent from secondary settling, CONV line
USP4: effluent from secondary settling, FCMT line
CSP3: effluent from aeration tank, CONV line
USP3: effluent from aeration tank, FCMT line
CSP5: re-circulated sludge, CONV line
USPS: re-circulated sludge, FCMT line
-243.3. List of analyzed parameters
The following groups are distinguished:
Group 1. General parameters
TSS
Total Suspended Solids (mg/L)
VSS
Volatile Suspended Solids (mg/L)
CODT
Total Oxygen Chemical Demand (mg 02/L)
CODS
Soluble Oxygen Chemical Demand (mg 02/L)
BODT
Total Oxygen Biochemical Demand (5 days) (mg 02/L)
BODS
Soluble Oxygen Biochemical Demand (5 days) (mg 02/L)
TKNT
Kjeldahl Total Nitrogen (mg/L)
TKNS
Kjeldahl Soluble Nitrogen (mg/L)
NH4-N
Ammonia Nitrogen (mg/L)
N03-N
Nitrate Nitrogen (m'g/L)
ALCALT Total Alkalinity (mmol HC03-/L)
P TOT
Total Phosphorus (mg/L)
P04-P
Dissolved Orthophosphate P (mg/L)
SULF T
Total Sulfides (mg/L)
CL"
Chlorides (mg/L)
O&G
Oils and Greases (mg/L)
Group 2. Special parameters
Phenols
Deterg.
Phenols (mg/L)
Anionic Detergents (mg/L)
CN-T
Total Cyanides (mg/L)
Ca T
Total Calcium (mg/L)
Mg T
Total Magnesium (mg/L)
-25
Cd T
Total Cadmium (mg/L)
Cr T
Total Chromium (mg/L)
Cu T
Total Copper (mg/L)
Ni T
Total Nickel (mg/L)
Pb T
Total Lead (mg/L)
Zn T
Total Zinc (mg/L)
As T
Total Arsenic (mg/L)
Hg T
Total Mercury (mg/L)
Group 3. Specific analyses of sludge
TSS
Total Suspended Solids (mg/L)
VSS
Volatile Suspended Solids (mg/L)
SVI
Sludge Volume Index (ml/g)
ESP. GRAV.
Specific Gravity
ISV
Initial Settling velocity (cm/min)
SV
Volume Settled Within 30 min (ml/L)
OUR
Oxygen uptake Rate (mg O^L. h)
SOUR
Specific Oxygen Uptake Rate (mg 0 2 /g.h)
H. BLANKET
Sludge Blanket Height (m)
MICROSCOPIC Examination
Analyses Schedule During Intensive Periods
On sewage samples: Type 1 (composite from 24 hrs)
-26
1
1 Frequency
1 Daily
| Three times
| per week
SPO
i
CSP1 | USPl
CSP4
TSS
CODT
BODT
TKNT
USP4 |
1
NH4-NI
VSS
CODS
BODS
TKNS
N03-NI
P04-P
Al cal
P TOT
Cl
0 &G
Ca
Fe
Pb
Phenols
Mg
Zn
Mn
Deterg.
Cu
Ni
Hg
Sulfides
Cr
Cd
Cyanides
On sludge samples: Types 5, 6 and 7 (grab samples, taken at 9, 15 and 01 hrs)
27 -
I
SP2-5 ¡SP2-6¡SP2-7¡SP5-5¡SP5-6¡SP5-7¡
1
i
|
|
i
I
i
TSS
|
I
i
SV
I
Blanket H
-
i
i
i
SP7
VSS
|
|
|
i
1 Daily
|
|
¡ Sp. Gr.j
| ISV
|
| OUR
|
|
¡Twice
|per Week
¡ Micro. ¡
| Anal
j
¡
j
|
|
¡Only Once,¡Ca
¡at the End¡Cu
¡of each
¡Fe
¡Intensive ¡Zn
¡Period
¡Pb Mn
|
Mg¡
Cr¡
Ni¡
Cd|
Hg¡
¡
i
|
|
i
i
|
|
|
|
|
i
l
¡
¡
|TSS VSS|
¡Ca
Mg¡
¡Cu
Cr¡
¡Fe
Ni¡
¡Zn
Cd|
¡Pb Mn Hg¡
During transition periods
During the transition periods the same analysis with the same frequency were
carried out as during the intensive periods, except for the sewage samples,
were the following parameters were omitted: CODs, BODg, TKNS and P
TOT. During the transition periods no samples were taken in SP7.
3.4. List of parameters measured in the plant on a continuous basis
All continuous measurement signals were received at a data acquisition unit
connected to an IBM PC computer, where they were processed by means of
the software Labtech. Notebook, the configuration of which enabled the data
-28-
to be instantaneously transmitted from each meter to the printer every 15
minutes; thus, a daily printout with 96 entries was produced. The data printed
every 15 minutes; represent the average value of all signals received during
such a period of time. Summary printouts were also produced daily, listing
the maximum, average and minimum values for each meter, as well as the
total values.
Parameters measured on a continuous basis are as shown below:
Instantaneous Measurements
1. Flow Rates
FI-1
FI-2
FI-3
FI-3'
FI-4
FI-4'
FI-5
FI-5'
Domestic sewage Influent
Industrial influent
Influent to the CONV line
Influent to the FMCT line
Sludge recirculation - CONV line
Sludge recirculation - FMCT line
Air to aeration tank - CONV line
Air to aeration tank - FMCT line
2. Temperatures
TI-1
TI-2
TI-2'
TI-3
TI-3'
Mixing tank for domestic sewage and industrial waste
Mixed liquor - CONV line
Mixed liquor - FMCT line
Secondary settler - CONV line
Secondary settler - FMCT line
3. pH
PHI-1
pHI-2
pHI-2
pHI-3
pHI-3'
Mixing tank for domestic sewage and industrial waste
Mixed liquor - CONV line
Mixed liquor - FMCT line
Secondary settler - CONV line
Secondary settler - FMCT line
294. Dissolved Oxygen
OIC-1
OIC-1'
Mixed liquor - CONV line
Mixed liquor - FMCT line
Totalized measurements
1. Flow Rates
FQ-1
FQ-2
FQ-3
FQ-3'
FQ-4
FQ-4'
FQ-5
FQ-S'
Domestic sewage influent
Industrial influent
Influent to the CONV line
Influent to the FMCT line
Sludge recirculation - CONV line
Sludge recirculation - FMCT line
Air to aeration tank - CONV line
Air to aeration tank - FMCT line
2. Power Input
Ul
U2
U3
U4
US
Blowers - CONV line
Recirculation pumps - CONV line
Blowers - FMCT line
Recirculation pumps - FMCT line
Recirculation pumps - FMCT line
3.5. Total number of samples and analysis
Research work covered a total of 610 days, split in 489 days of transition
periods and 121 days of intensive periods. The number of samples processed
during the transition periods is estimated at 8,313, on which 55,743 parameters were analyzed; during the intensive periods some 2,071 samples were
taken and a total of 16,397 parameters analyzed.
Therefore, the total number of samples taken during the investigation was
10,384, on which 72,140 parameters were analyzed.
-303.6. Scientific and technical team
Miguel Lueje (CAGB - Mechanical Engineer)
Alejandro de la Sota (CAGB - Biologist)
Alberto Gómez (CAGB - Assistant Mechanical Engineer)
Prof. Peter Grau (Scientific Consultant, President of IAWPRC)
Prof. Mogens Henze (Technical university of Denmark, Modelling Expert)
René Dupont
(Technical University of Denmark, Modelling Expert)
Analytical Control
Karmele Zaballa (Biologist)
Juan M' Cenigaonaindia (Chemist)
Cristina Arrieta (Chemist)
José Antonio González (Chemical Technical Engineer)
Itziar Unzueta (Biologist)
Roberto Colino (Biologist)
Ma Jesus Citores (Chemist)
Marian Bilbao (Chemical Technical Engineer)
Itziar Aretxabala (Chemical Technical Engineer)
Pilot Plant Operation
Luis Angel Bilbao,
Coordinator (Merchant Navy Chief Engineer)
Ricardo Gómez (Electronics Technician)
Rafael López Heredia (Electronics Technician)
Antonio Malave (Electrical Technician)
Vicente Carro (Mechanical Technician)
An tol in Trancho (Electronics Technician)
Francisco Gutiérrez (Electrical Technician)
Esteban Garcfa (Electronics Technician)
Iñaki Zorrilla (Energetic Efficiency Technician)
31
3.7. Analytical Methods
All analytical methods employed conform to "Standard Methods for Sewage
Analysis", 17th Edition, 1989.
The analytical methods used are listed hereunder.
3.7.1. General Parameters
TEMPERATURE
pH
DISSOLVED OXYGEN
TOTAL SOLIDS
TSS
VSS
CODT
CODs
BODT
BODs
TKNT
TKNS
NH4-N
NO3-N
ALKALINITY
PTOTAL
P04-P
SULPHATES
TOTAL SULPHIDES
CHLORIDES
OILS & GREASES
Meter installed in the plant
Meter installed in the plant
Meter installed in the plant
Evaporation and drying at 105°C. Gravimetry
Filtering through glass fibre. Drying at 105 °C.
Gravimetry
Filtering. Ignition at 550°C. Gravimetry
Open reflux method. Oxidation by potassium
dichromate for two hours.
Membrane filtering. Two hours of open reflux
Dilution method. Dissolved oxygen
readings through probe
Membrane filtering. Dilution method
Acid digestion. Distillation and ammonia analysis.
Membrane filtering and application of the abovenamed method
Nessler colorimetrie method
Chromotropic acid method
Neutralization at Ph = 3.7
Acid digestion, orthophosphates analysis
Vanadate-Molybdate method.
Precipitation with barium salts. Gravimetry
Precipitation. Filtering and titration with sodium
thiosulphate
Titration with silver nitrate
Extraction by freon. Evaporation and
gravimetry.
3.7.2. Special Parameters
PHENOLS
Distillation and colorimetry of distillate with 4aminoan tipyrine. Prior extraction with chloroform.
-32
ANIONIC DET.
TOTAL CYANIDES
TOTAL METALS
Standard LAS. Colorimetry with methylene blue.
Distillation in acid medium. Selective electrode
method
Digestion by nitric acid. Analysis of metals by means
of atomic absorption spectrophotometry.
3.7.3. Sludge Analysis
TSS
VSS
SET. VOLUME
SPEC. GRAV.
ISV
OUR
BLANKET HEIGHT
MICR. ANALYSIS
Filtration through glass fibre. Drying at 105°C.
Gravimetry.
Filtration. Ignition at 550°C. Gravimetry
30-minute settling in a 1-litre cylinder.
Gravimetry
Settling curve in a 2-litre graduated cylinder
Probe measurement of the oxygen decay rate in a
BOD bottle
Height in meter from the bottom of the settling tank
to the interphase between the settled sludge and the
supernatant.
Observation of sludge under the microscope. GRAM
and NEISSER staining.
-334.
OPERATING STRATEGY
The plant has been treating a mixture of domestic sewage and industrial
waste of the following constant ratio:
85% by volume - domestic
15% by volume - industrial
The industrial waste was prepared from concentrated pickling liquors. The
final mixture had a concentration of approx. 20 ppm iron. Iron was the
component with the highest concentration in the industrial waste that was
handled.
Pumping facilities for the domestic sewage were located in a municipal
collector at Sestao, from August 1989 till June 1990. Pumping was continuous
from 06 hrs to 22 hrs; there were conditions of intermittent pumping during
the night due to the low flow rate of the collector, aggravated by the drought
and the water supply restrictions that prevailed in the district during that
time.
From June 1990 till the completion of the Project, the pumping facilities were
located at the Galindo Treatment plant, pumping being constant 24 hours a
day ever since.
Control and operation of the plant was carried out, throughout the project, by
the responsible technical personnel, 24 hours per day, 7 days per week.
The start-up of the pilot plant, prior to the formation of biomass in the
aeration tanks, was based on domestic sewage. During that time, operating
conditions in both lines were maintained as follows: 3 m3/h influent rate,
100% recirculation and dissolved oxygen levels of 2.5 mg/L.
-34-
Once sufficiently high concentrations of MLSS were reached, the
acclimatization phase for industrial waste was initiated. Industrial waste was
prepared from pickling liquors with high acidity and metal concentration
(HCl-Fe and H2S04-Cu-Ni).
This mixture was diluted with clean water and mixed prior to entering the
plant, with no previous neutralization. The concentration was increased by
10% daily, until 100% was dosed in ten days time.
Once 100% of industrial waste was reached in the mixture to be treated, a
considerable deterioration of the effluent was observed and it was, therefore,
decided to neutralize the industrial waste at Ph = 7 prior to the treatment.
The pre neutralization was effected with NaOH.
Influents treated in each line were:
2.5 m3/h
0.5 m3/h
Total
= 3.0m3/h
Domestic sewage
Industrial waste
Mixture
From that moment on, the operating strategy can be divided into two parts,
depending on the fundamental parameter of the process control selected:
Control Parameter: Sludge Age (9x)
Control Parameter: Mass Load ratio (F/M)
4.1. Control Parameter ; Sludge Age (8x1
Operation criteria for periods 1, 2 and 3.
As operating conditions we considered: dissolved oxygen, the recirculation
rates and wasting rates.
-354.1.1.
Conventional line
Dissolved Oxygen
The D.O. concentration in the aeration tank was kept at a preset value, 1.5
mg/L, by means of an oxygen controller which receives a signal from a meter
of the electrode probe type which, depending on the set point, actuates a
speed variator which regulates the blowers, which respond to changes in the
dissolved oxygen. The blowers increase or decrease the air supply to the
aeration tank.
Recirculation Rate
Departing from the result of the 30-min settling test, the recirculation rate to
be applied was calculated as follows:
Qr
SV
Qi
1000 - SV
where: Qr
x 100
(4.1)
Recirculation flow
Qi
Influent flow
SV
Settled volume after 30 minutes.
Figure 4.1 can be used to calculate the recirculation rate as a function of the
settled volume.
Wasting rate
When the sludge age established in each case is known, the wasting rate
needed to maintain the sludge age constant is calculated as follows:
Fig.4.1.Chart for calculation of recycle
flow as a function of settled volume
test.
Recycle (low (%)
GO
O)
150
200
250
300
Settled volume (SV ml/L)
350
400
450
500
37Va
SSe. Qi
Øx
MLSS
Qw =
where: Qw
v innn
i A 'M
Wasted flow (l/d)
Va
Volume of aeration tank (m3)
Gx
Sludge age (d)
SSe
Total suspended solids in effluent (kg/m3)
Qi
Influent flow (m 3 /d)
MLSS
Total suspended solids in mixed liquor (kg/m3)
Wasting was carried out intermittently from the mixed liquor.
Another factor which was taken into account when carrying out the
recirculation rate and wasting operations was the height of the sludge blanket
in the secondary settling tank which, occasionally, due to bad settling
characteristics of the sludge, rose to the extent that it caused loss of solids
into the effluent. To preserve the characteristics of the effluent, the option
was taken to increase the rate of recirculation by an additional 50% for two
hours, with a maximum limit of 4.5 m3/h, and to waste 1 m3 of mixed liquor.
4.1.2. FMCTLine
Dissolved Oxygen
D.O. in the aeration tank was controlled automatically in the same way as in
the conventional line and kept at a level of 2.5 mg/1.
-38Recirculation rate
Initially, the recirculation rate was adjusted three times per day, calculations
being made according to the above formula (4.1). Later, recirculations in the
40 - 60% range were effected and, finally, recirculation rate charts were used,
calculated as a function of the variation in the total organic load. Adjustment
took place every hour.
One of the charts used is shown in Figure 4.2.
Wasting rate
Wasting was taken from the mixed liquor three times a day, at 8 h intervals,
calculated as per formula (4.2). Each wasting was 1/3 of the total daily waste.
To facilitate calculations, individual charts for each sludge age were designed,
wherein the wasting rate is given as a function of the total suspended solids in
the effluent and the total suspended solids in the mixed liquor.
One example is shown in Figure 4.3
42.
Control parameter : Mass load ratio (F/MÌ
It was the operating criteria during periods 4, 5, 6 and 7. Control was the
same for both lines. The operating parameters considered in this case are:
dissolved oxygen, influent flow rate, recirculation rate and sludge wasting.
Fig.4.2.Recycle flow curve used in FMCT
line for periods 2 and 3.The curve fo
llows the CODi variation in 24 h.
Reoycle Flow (%)
00
—
80-
—
......
60-
•
■
•
1
40-
\
i
v
........
■■.
\
20-
o-
1
1 —
i
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Hours
Fig.4.3.Chart for calculation of wasting
flow as a function of MLSS and TSSe for
0a-2O days.
300
250
200-
15010050-
Qw (L/8 hours)
-—
SSe-10ppm
-+-
SSe«20ppm
-*-
SSe-30ppm
-B-
SSe-40ppm
-K-
SSe-50ppm
-e-
SSe-60ppm
-A
SSe-70ppm
-S-
SSe-80ppm
o
-41 Dissolved Oxygen
The set point for CONV line = 1.5 mg/1, FMCT line = 2.5 mg/1, being
established, this was maintained automatically as described above. Higher DO
in FMCT line was selected to provide sufficient concentration gradient of
oxygen for the higher MLSS.
Influent Flow Rate
After establishing the F/M ratio to be maintained during the period under
consideration, the influent flow rate was calculated daily, depending on the
volatile suspended solids 'in the mixed liquor and the chemical oxygen
demand of the influent, by applying the following formula:
F/M . MLVSS . Va
Qi =
BOD
(4.3)
BOD = 0.44 COD
where: Qi
BOD
Influent flow (m3/d)
Biochemical oxygen Demand (kg/m3)
MLVSS Volatile suspended solids in mixed liquor (kg/m3)
Va
Aeration tank volume (m3)
COD
Chemical Oxygen Demand (kg/m3)
This is displayed in Fig. 4.4.
Recirculation rate
This was adjusted as high as necessary, to prevent sludge from floating in the
secondary settling tank as a result of de-nitrification. During low-temperature
periods, when these flotation problems did not occur, the recirculation rates
were smaller, about 50%.
Fig.4.4.Chart for calculation of in
fluent flow as a function of MLVSS
and CODi for F/M ■ 0.5
Ql (m3/h)
■Iß—,
1D
141210-
I
—*— C O D - 3 0 0 mg/l
-4-
C O D - 3 5 0 mg/l
-*-
C O D - 4 0 0 mg/l
-B-
C O D - 4 5 0 mg/l
-*-
C O D - 5 0 0 mg/l
~~r^\
Ä—*
8-
^^^"^
\
\
6- -
<£~*<Z^ fr__
4j
^
"
*
^
^
^
"
*
"
"
^
—
2-
o500
1000
1500
2000
2500
3000
MLVSS (mg/l)
3500
4000
4500
5000
-43Wasting rate
Wasting were carried out depending on the height of the sludge blanket in
the secondary settler.
During high-temperature periods (4 and 5), limits of 3.2 m for the CONV
line and 3.7 m for the FMCT line were established.
Considering that the concentration of total suspended solids in the effluent
was too high with respect to good sludge settling characteristics during hightemperature periods and on the assumption that this might be due to
excessive blanket height, the decision was made to decrease it; for lowtemperature periods (6 and 7) the limits were set at 2 m. for the CONV line
and 3.5 m. for the FMCT line.
-44RESULTS
In this chapter are included all the average results for each intensive period.
This results are discussed later in chapter 7.
45
TABLE 5.1.
OPERATING CONDITIONS IN INTENSIVE PERIODS
TABLE 5.2.
HYDRAULIC DATA
TABLE 5.3.
INFLUENT TO PILOT PLANT (Domestic & Industrial)
TABLE 5.4.
METALS IN INFLUENT TO PILOT PLANT (Domestic & Industrial)
TABLE 5.5.
PRIMARY CLARIFIERS EFFLUENT CSP1/USP1
TABLE 5.6.
METALS IN PRIMARY CLARIFIERS EFFLUENT CSP1/USP1
TABLE 5.7.
FINAL EFFLUENTS CSP4/USP4
TABLE 5.8.
METALS IN FINAL EFFLUENTS CSP4/USP4
TABLE 5.9.
DIURNAL VARIATIONS CONVENTIONAL SYSTEM
TABLE 5.10.
DIURNAL VARIATIONS FMCT SYSTEM
TABLE 5.11.
ACTIVATED SLUDGE MASS BALANCE (1)
TABLE 5.12.
ACTIVATED SLUDGE MASS BALANCE (2)
TABLE 5.13.
SLUDGE QUALITY
TABLE 5.14.
METALS IN PRIMARY SLUDGE CSP7/USP7
TABLE 5.15.
METALS IN ACTIVATED SLUDGE CSP2/USP2
TABLE 5.16.
AERATION PARAMETERS
TABLE 5.17.
ENERGY CONSUMPTION
TABLE 5.18.
SLUDGE AGE CALCULATION
TABLE 5.1: OPERATING CONDITIONS IN INTENSIVE PERIODS
PERIOD
DATE
FA< (kgBOtVkgMLVSS.day)
1
2
16-29 Jan 90 26Feb-26Mar 90
CONV
FMCT
FMCT
CONV
3
16-30 May 90
CONV
FMCT
4
9-24 Jul 90
FMCT
CONV
5
20Aug-3Sep 90
CONV
FMCT
6
14-31 Jan 91
CONV
FMCT
7
18Feb-8Mar91
CONV
FMCT
0,376
0.275
0,405
0.174
0,645
0,22
0.205
0,162
0,4
0.2S2
0,231
Temperature (deg C)
12,9
13.2
15.6
16.4
19.3
19.7
20.6
20,5
22,7
22.6
11.6
8.6
6.4
6.1
Primary aettllng
Yes
Yes
Yes
Yes
No
No
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Influent flow (Ql) (m'/h)
1.51
3.44
5.9
6.2
2.56
3.14
1.76
6.58
0,207
0.579
0.429
2.53
2.54
2.07
2
2.S
2,3
Recycle flow (Or) (m'/h)
1.91
1.54
1.59
1.56
1,56
6,39
3
9
1.77
4.76
1.26
1.57
1.11
3.29
D.O. (mg/l)
0,97
2.65
1.6
2.07
1.64
1,56
1.53
2.5
1.4
1.4
1.63
2.65
1.93
2.51
1.6
No Detec
1.3
1.5
1.7
1.8
2.9
1.8
3.3
Blanket level (m)
2.1
1.4
2,5
3.1
2.9
pH
7,4
6.8
7.4
7,3
7.4
6.2
6.3
6.2
6.6
6.8
7.4
7.3
7.5
7.2
Total sludge age (daya)
9,6
11.5
6.7
47.4
4.2
27.1
36,8
31,4
10.0
19,7
12.0
.44.4
4.6
13.6
2642
3630
2194
5091
1420
5009
1097
3708
3136
5606
2346
3067
650
3616
MLVSS (mo/I)
Recycla VSS (mg/n
6912
10621
5062
11450
3470
7804
2400
5500
12485
16860
6324
8963
2032
9356
U (KgBOO/kgVSS.day) (1)
0.318
0.254
0.36
0,166
0.795
0,2
0,165
0,153
0.375
0.26
0.22
0.193
0.534
0.392
Sludge wasted (kgVSS/day) (2)
2.036
0.17
6.972
0.789
6
0,702
0
0
0
0
5.416
1.989
3.582
13.43
Effluent sludge (kgVSS/day) (3)
4.752
1.987
1.63
1.273
2.467
3.651
0.7
1,676
4.674
5.335
0.614
0.511
0.349
1.607
Sludge wasted and lost (4)
(KgVSS/day)
6.767
2,157
8.602
2.061
10.467
4.353
0.7
1.876
4.874
5.335
6.031
U
3.931
15.237
0.83
0.B1
0.80
0.76
0.82
0.75
0,79
0.75
0.75
0.73
0.66
0.62
0.73
0.65
MIVSS/MLSS
UUzatlon rata (kg BOO removed/kg MLVSS.(Jay)
Sludge wasted - OwJCa
Effluent sludge • (QI-Ow).VSSe
Sludge wasted and lost - (Ow.Xa) ♦ (QH}w).VSSa
TABLE 5.2: HYDRAULIC DATA
PERIOD
DATE
2
1
16-29 Jan 90 26Feb-26Mar 90
CONV
FMCT
CONV
FMCT
3
16-30 May 90
CONV
FMCT
4
9-24 Jul 90
CONV
FMCT
5
20Aug-3Sep 90
CONV
FMCT
6
14-31 Jan 91
CONV
FMCT
7
18Feb-BMar91
CONV
FMCT
a (domestic ♦ lndustriai)(m'/1i)
2.53
2,54
2,07
2
2,5
2,3
1.51
3.44
5,9
6,2
2.56
3,14
1,76
6.58
Q Industrial (m'/h)
0.37
0.36
0.31
0.31
0,33
0.31
0.19
0,45
0.24
0.34
0.31
0,39
0.14
0,54
Overflow Rate P.S. (m/h)
0.66
0.66
0.55
0,55
0.39
0,9
1.55
2.15
0.67
0.62
0.46
1.73
Retention Time P.S. (h)
4.35
4.33
5.24
5,24
7.29
3.2
1.66
1.34
4,3
.3.5
6.18
1.67
Retention Time A.S. (h)
4,05
4,41
4,67
4,91
4.43
2.7
3.99
1.44
2.34
1.38
4.66
3.62
6,22
1.62
Overflow Rate S.S. (m/h)
0,66
0,2
0,55
0,16
0,65
0,16
0,39
0,27
1,55
0.65
0,67
0,25
0,46
0,52
Retention Time S.S. (h)
4,35
15.93
5.24
19.27
4,4
17,59
7,29
11,76
1.66
4,93
4,3
12.66
6,16
6,15
Solids Surface Load S.S.
(kg/m'.h)
3,62
1,41
2,67
1,95
1.65
4,6
1.65
4,9
6.17
7.76
3.62
1.91
0,64
4.15
2,1
1.4
2,5
3.1
2,9
1.6
No detec
1,3
1.5
1.7
1.6
2,9
1,6
3,3
1.91
1,54
1,59
1,56
1,56
6,39
3
9
1.77
4,76
1,26
1,57
1,11
3.29
Blanket level (m)
<» (m'/h>
P.S.
Primary Settler
A.S.
Activated Sludge
S.S.
Secondary Settler
Or
Recirculation flow
TABLE 5.3: INFLUENT TO PILOT PLANT (Domestic & Industrial)
PERIOD
DATE
2
1
16-29 Jan 90 26Feb-26Mar 90
3
16-30 May 90
4
9-24 Jul 90
S
20Aug-3Sep 90
6
14-31 Jan 91
7
18Feb-8Mar 91
SS (mg/l)
262
343
237
232
260
250
319
VSS (mg/l)
217
260
190
150
177
169
213
B005T(mg/t)
386
375
377
194
234
207
236
148
146
166
35,5
44,9
63
70.3
COO T (mg/l)
1000
622
717
409
508
422
562
COD S (mg/l)
323
330
109,4
127
156
156
TXNT(mg/I)
90.1
61
34,5
34,3
43,9
483
TKN S (mg/l)
74.3
70
23,5
23.5
34,9
37.7
N-NH, (mg/l)
70.6
72.4
63.4
24,4
23.9
30,2
32
N-NO, (mg/l)
0.5
0.3
0.4
0,2
0.2
0,4
0.3
11.4
10,4
14.2
6,1
5.6
5.5
5,8
7.0
9.1
13.2
5.4
5.3
2.5
3.8
8.46
6.46
7.72
4.62
5,98
4,76
4.32
56.3
28,5
51.6
32.3
54,5
B005 S (mg/1)
TOTAL P (mg/l)
P-PO. (mg/l)
ALKAUNITY (mmol/HCO,-)
96
OIL l OREASE (mg/l)
173
66,6 '
SULFIDE (mg/l)
1.5
1.9
2
1.2
1.8
1
1.3
CHLORIDE (mg/l)
142.5
143
91.9
407.6
445.3
233.6
487.9
PHENOLS (mg/l)
0,05
0,043
0,013
0.011
0,052
0.186
SURFACTANTS (mg/l)
12.S
14.4
7.2
8.9
6.8
11.1
CYANIDE T (mg/l)
0.S2
0,178
0.139
0.052
0.15
0.19
14.4
Average values In every period.
CO
TABLE 5.4: METALS IN INFLUENT TO PILOT PLANT (Domestic & Industrial)
PERIOD
DATE
1
2
16-29 Jan 90 26Feb-26Mar 90
3
16-30 May 90
4
9-24 Jul 90
5
20Aug-3Sep 90
6
14-31 Jan 91
7
18Feb-8Mar 91
CaT(mg/l)
50.6
46.1
37,6
72.6
92.2
97.2
129
Mg T (mg/1)
7.4
7,3
5,9
23.1
36.4
24.1
49,3
Cd T (mg/l)
0.003
0,003
0,003
0,002
0.005
0.004
0.004
Cr T (mg/1)
0,049
0.04
0,023
0,045
0,031
0.013.
0,015
Cu T (mg/l)
0.069
0.072
0,065
0.097
0,074
0.06
0,069
Fe T (mg/l)
20
19.6
6.5
24,9
23,5
19
17.3
Mn T (mg/l)
0.191
0.169
0.1
0.239
0.247
0.234
0.233
NI T (mg/l)
0,129
0.126
0.O97
0.131
0,07
0.125
0.091
Pb T (mg/1)
0.076
0,075
0,072
0.09
0,102
0.079
0.075
Zn T (mg/l)
0.257
0,221
0.274
0.25
0.277
0.202
0.126
Average values in every period.
4*
CO
TABLE 5.5: PRIMARY CLARIFIERS EFFLUENT CSP1/USP1
PERIOD
DATE
1
2
16-29 Jan 90 26Feb-26Mar 90
CONV
FMCT CONV
FMCT
3
16-30 May 90
CONV
FMCT
4
9-24 Jul 90
CONV
FMCT
5
20Aug-3Sep 90
CONV
FMCT
6
14-31 Jan 91
CONV
FMCT
7
18Feb-8Mar 91
CONV
FMCT
SS (mg/l)
179
194
63.6
109
133
132
138.2
139.3
158
177
VSS (mg/l)
141
151
63.7
62,8
96.6
99.6
99.3
100.1
113
123
B0O5 T (mg/l)
295
316
114
133
159
143.5
159.1
153.1
161
174
BOOS S (mg/l)
144
145
41
43
57.8
45.5
63.6
63
83
73
COD T (mg/l)
640
674
256
285
326.6
322.4
331.3
341.1
406
418
COD S (mg/l)
29a
116
111
137
139
137.5
140
171
166
TKN T (mg/l)
79
65.2
30.1
30
33.2
33
39.9
39.8
46.6
43.3
TKNS(mg/l)
67
23.6
23.6
26
24.5
33,7
33.5
37.6
36.3
N-NH, (mg/l)
66.4
24.5
23,4
25.2
24,8
29.7
26.4
32.8
30.6
0,4
0.1
0,3
6
5.6
66.1
0.3
0.2
0.2
0,2
0.21
0.16
0,3
TOTAL P (mg/l)
11.4
10.1
6.9
6.7
5,8
5,7
5.1
4,9
P-PO, (mg/l)
11.9
10
5.6
S.5
S.9
S.5
2.7
2,6
4.9
4.1
4.24
519
N-NO, (mg/1)
ALKAUNrTY (mmol/HCO,)
7.76
6.12
OIL t, GREASE (mg/l)
56,9
51.9
1.7
2.1
133.9
132
SURFACTANTS (mg/l)
11.8
14.3
CYANIDE T (mg/l)
0.37
0.22
SULFIDE (mg/l)
CHLORIDE (mg/l)
PHENOLS (mg/l)
Average values In every period.
4.52
4.32
6.16
5.22
4,6
4,56
4,42
295
363
423
381
217
207
438
TABLE 5.6: METALS IN PRIMARY CLARIFIERS EFFLUENT CSP1/UPS1
PERIOD
DATE
Ca T (mg/))
2
1
16-29 Jan 90 26Feb-26Mar 90
CONV FMCT CONV FMCT
41.7
3
16-30 May 90
CONV FMCT
4
5
9-24 Jul 90 20Aug-3Sep 90
CONV FMCT CONV FMCT
6
14-31 Jan 91
CONV FMCT
7
18Feb-8Mar91
CONV FMCT
41.8
Mg T (mg/l)
6.6
6.6
Cd T (mg/I)
0.003
0,002
Cr T (mgfl)
0.019
0,026
0,009
0.013
0,016
0.018
0.006
0.005
0.008
0,008
0.03
0,037
0,037
0,039
0.039
Cu T (mg/I)
0,036
0,046
0.026
0,032
0.031
Fe T (mg/1)
6.6
6.9
5,6
9
9.1
10.5
7.19
7.32
6,41
6.93
Mn T (mg/I)
0,125
0.105
NI T (mg/I)
0,093
0.096
0,072
0,095
0.044
0.047
0.091
0.092
0.068
0,069
Pb T (mg/I)
0,043
0.05
ZnT (mg/I)
0.154
0.172
Average values In every perlod.
TABLE 5.7: FINAL EFFLUENTS CSP4/USP4
PERIOD
DATE
1
2
16-29 Jan 90 26Feb-26Mar 90
CONV
FMCT
CONV
FMCT
3
16-30 May 90
CONV
FMCT
4
9-24 Jul 90
CONV
FMCT
5
20Aug-3Sep 90
CONV
FMCT
6
14-31 Jan 91
FMCT
CONV
95
39.1
41.4
30
53.6
82.9
32,6
27,9
47.2
36.6
12,3
VSS (mg/l)
79.3
32.6
34.9
26
45.7
66.4
26.7
22,7
34.3
27.1
B005 T (mg/l)
54.S
27.8
17.6
17
25.2
38.2
12.7
9.5
16.9
10.8
BOOS S (mg/l)
5.5
4.6
2.2
3
3.9
1.7
2.6
2.5
2.5
COD T (mg/l)
233
134
103
112
COD S (mg/1)
74
79.7
SS (mg/1)
TKN T (mg/l)
50.9
29,4
TKNS(mg/l)
41.9
25,3
N-NH3 (mg/1)
43
N-N03 (mg/l)
6.4
TOTAL P (mg/l)
7
18Feb-8Mar91
CONV
FMCT
8.1
12,5
16.3
10,3
7
9.3
11.7
6
7.1
9
10.9
1,3
2.3
2.7
4.3
4.3
132
143
74.9
64,5
93.3
74.1
SI .6
56
68
67.3
62.8
46.4
27,9
28.1
40
30.4
34
36
47.4
46.9
53
15.5
7,6
7.2
11.9
7.9
31.2
30.5
30.6
30.8
70.1
70.2
47.5
9.8
5.3
5.1
7.1
5.9
28,8
28.3
29.2
29
25,6
56.7
61
46.4
5.2
0.5
0.5
6
Z.8
25,7
25.6
23.2
24.7
11.6
0.5
1.8
0.6
23.7
22.8
22.7
16.6
16.7
0,6
0.6
0.3
0.1
9
9
7.7
7.5
10.9
12,2
5.3
5.8
4.5
4.7
2.8
1.3
3.4
2.4
P-P04(mg/I)
7.9
6.7
6.5
7.8
9.7
11.4
4.4
4.5
4,4
4.5
2.3
0.7
2.5
1.8
ALKALINITY (mmol/HCO,")
5.0
3.2
7.02
7.06
5.74
1.28
0.56
0.64
2.26
2.14
4.16
4.16
3.S4
3.70
127.2
129.8
134.4
133,9
91.6
86.4
276.1
297.8
448.1
457.4
192.9
190
432.2
472.4
1.68
1.4
0.45
0.49
0.04S
0,045
OIL t GREASE (mg/l)
SULFIDE (mg/l)
CHLORIDE (mg/l)
PHENOLS (mg/l)
SURFACTANTS (mg/l)
CYANIDE T (mg/l)
Average values In every period.
Ol
M
TABLE 5.8: METALS IN FINAL EFFLUENTS CSP4/USP4
PERIOD
DATE
CaT(mg/l)
2
1
16-20 Jan 90 26Feb-26Mar 90
CONV FMCT CONV FMCT
49,1
47,2
41
41,1
3
16-30 May 90
CONV FMCT
34,4
4
5
9-24 Jul 90 20Aug-3Sep 90
CONV FMCT CONV FMCT
6
14-31 Jan 91
CONV FMCT
7
18Feb-8Mar91
CONV FMCT
36,9
Mg T (mg/I)
6,97
e.55
6.18
6,17
4,68
9,13
Cd T (mg/I)
0,003
0,002
0,002
0.002
0.002
0.002
Cr T (mg/I)
0.016
0.006
0.011
0.007
0,005
0,014
0.019
0,007
0.011
0.011
0,001
0,001
0,003
0.003
Cu T (mg/I)
0,043
0,026
0.015
0,011
0,01
0,024
0,016
0,017
0,015
0,012
0.011
0.019
0,011
0.01
Fe T (mg/I)
9,4
1,6
1.69
1,02
0,72
3,56
0,37
0.67
0.7
Mn T (mg/I)
0,104
0,092
0.062
0,059
0,037
0.069
0.1
0,063
0.073
0,071
0,03«
0,055
0,061
0,06
0.059
NI T (mg/I)
PbT(mg/I)
0,039
0,026
0,019
0,017
0,024
0,031
ZnT(mg/l)
0,149
0,113
0.033
0,042
0,064
0,019
1.5
1.56
3.56
2,22
0.52
0,064
0,06
0,036
0,031
0.063
Avenge values In every perlod.
Ol
CO
TABLE 5.9: DIURNAL VARIATIONS CONVENTIONAL SYSTEM
DATE: 12-Mar-91 (10:00h a.m.) to 13-Mar-91 (8:00h a.m.). Dry weather conditions.
HOUR
Primary clarifier effluent
mg/l
mg/l
mg/l
COD-T COD-S TKN-T
mg/l
N-NH3
Final effluent
mg/l
mg/l
COD-T COD-S
mg/l
COD-T
Mixed liquor
mg/l
mg/l
COD-S N-NH3
Recycle sludge
mg/l
COD-T
10
323
151
37
29
59
46
697
69
26
2475
12
292
13S
36
32
61
46
551
63
26
1743
14
319
151
45
3a
49
46
844
61
26
1377
67
29
2036
29
2109
16
403
159
45
36
49
44
756
16
356
151
45
35
49
44
1019
63
20
348
159
43
36
49
44
873
53
28
2109
52
26
2546
27
2914
22
364
162
39
30
56
44
697
24
360
143
31
23
49
44
580
46
2
311
131
29
22
49
37
551
54
28
2109
52
25
1616
4
253
111
23
18
49
26
990
6
222
115
22
17
49
28
756
44
25
1743
6
216
67
20
18
52
32
287
36
25
1616
AVERAGE
314
139
34
27
51
40
716
55
27
2066
MAX
403
162
45
38
61
46
1019
69
29
2914
MIN
216
67
20
17
49
28
267
36
25
1377
NOTE: CSP1 samples were taken from 13 Mar 91 to 14 Mar 91. with heavy rain between 2 am to 6 am (1< Mar 91)
Operating conditions tn the Plant as Pertod 7.
CTI
TABLE 5.10: DIURNAL VARIATIONS FMCT SYSTEM
DAY: 12-Mar-91 (10:00h a.m.) to 13-Mar-91 (8:00h a.m.). Dry weather conditions.
Hour
Primary clarifier effluent
mg/l
mg/l
mg/l
COD-T COD-S TKN-T
10
190
12
364
14
475
16
568
251
mg/l
N-NH3
Final effluent
mg/l
mg/l
COD-T COD-S
Mixed liquor
mg/l
mg/l
COD-T COD-S
27
20
SB
41
177
71
56
56
46
4968
273
62
47
49
32
4733
42
26
79
44
3445
112
3445
mg/l
N-NH3
Recycle sludge
mg/l
COD-T
31
19008
173
36
19740
160
51
17397
113
38
21790
127
IB
745
333
39
26
70
46
5612
169
29
21937
20
606
257
34
22
73
57
4499
95
43
21790
22
407
205
26
19
73
55
4323
B1
30
22B15
24
230
130
20
15
79
53
3503
50
24
20765
11
79
52
3503
40
23
19008
9
79
53
3737
35
23
21056
2
162
96
15
4
135
63
13
6
79
36
6
S
73
53
3503
44
25
20912
e
63
■ 44
10
7
73
53
4323
40
25
19008
AVERAGE
336
164
30
22
70
46
4132
95
31
20436
MAX
745
33
71
56
79
57
5612
160
51
22815
MIN
79
36
6
5
49
32
3445
35
23
17397
.
NOTE: USP1 samples were taken from 13 Mar 91 to 14 Mar 91, with heavy rain between 2 am to 8 am (14 M ar 91)
Operating conditions in the Plant as Period 7.
Ul
TABLE 5.11: ACTIVATED SLUDGE MASS BALANCE (1)
PERIOD
DATE
1
2
16-29 Jan 90 26Feb-26Mar 90
CONV
FMCT
CONV
FMCT
3
16-30 May 90
CONV
FMCT
4
9-24 Jul 90
FMCT
CONV
5
20Aug-3Sep 90
FMCT
CONV
6
14-31 Jan 91
FMCT
CONV
7
18Feb-8Mar91
FMCT
CONV
Blanket level 0 (m)
2,9
0,49
2.93
2,67
3.27
1.63
No detec
1.17
1.63
1.77
1.97
3,10
1.6
3.4
Blanket level 1 (m)
2.3
1,75
2.97
3,7
2.3
1.45
No detec
1.33
2,55
1.97
1.43
2,9
1.9
3.27
Recycle VSS 0 (kg/m')
5.22
9,06
5,71
11.10
3.72
6.70
2,49
4.67
5.62
9.37
7.116
6.664
2.918
6,2
Recycle VSS 1 (kg/m*)
6.61
11,38
2.72
11.02
3.92
8.06
2.42
4.93
12.628
20.924
5.428
11.924
1.264
9.412
MLVSS 0 (kg/m1)
2,59
2,796
2.20
4.27
1.52
4.68
1.20
3.66
2.67
5.40
2.94
2.84
0.63
3.72
MLVSS 1 (kg/m")
3.77
4,819
1.63
5.11
1.55
4.80
1.07
4.30
3.20
S.13
1.65
3.33
0,74
3.86
Sludge volume In settler 0 (m1)
6.71
0,14
6.63
20.5
6.23
5.24
0
1.94
1.9
6.72
3.16
23.36
233
27,15
Sludge volume In settler 1 (m3)
4,43
G.49
6.98
30.92
4.43
3.69
0
2.85
5.36
9.18
1.26
20.87
2.91
25.52
VSS In settled sludge 0 (kg/m ) (1)
3,47
4.55
3.37
6,55
2.2S
5.35
1.63
4.20
3.65
6.72
4,33
4.76
1.93
5.21
VSS In settled sludge 1 (kg/m*) (1)
4.72
7.01
1,99
7.06
2.34
5.69
1.52
4.51
6.34
10.39
2,91
6.19
0.91
5.71
Sludge mass In settler 0 (kg)
23.26
0.64
23,02
134.21
18.54
28.05
0
8,14
6.94
45.16
13,76
111.76
3.8S
141,54
Sludge mass In settler 1 (kg)
20.69
45.47
13.91
216.91
10.37
21.72
0
12,85
34.13
95.41
3,72
129.25
2.66
145.72
Sludge mass In alratlon tank 0 (kg)
46.62
50.22
39.60
76.66
27.36
64.24
21.60
69.5
48.06
97.20
52.92
51.12
14.94
66.96
Sludge mass In alratlon tank 1 (kg)
67.66
66,76
29.34
91,98
27.90
86.40
19.26
77.40
57.60
92.34
29.70
59.94
13,32
69.46
1
(1) VSS In settler sludge - (2 . MLVSS + Recycle VSS)/3
0 - Beginning of period
1 - End ot period
Ol
TABLE 5.12: ACTIVATED SLUDGE MASS BALANCE (2)
PERIOD
DATE
2
1
16-29 Jan 90 26Feb-26Mar 90
FMCT
CONV
CONV
FMCT
14
Removed BODS (kg/day)
Sludge mass 1 A.S. (kg)
4
9-24 Jul 90
CONV
FMCT
5
20Aug-3Sep 90
FMCT
CONV
6
14-31 Jan 91
CONV
FMCT
7
18Feb-BMar91
FMCT
CONV
14
29
29
15
15
16
16
15
15
18
16
19
19
6.79
2.16
a.60
2.06
10.49
4.35
0.70
1.86
4.87
5.34
6.03
2.50
3,93
15.24
14.5
16.3
15.0
15.2
19.9
16.0
3.6
10.1
20.2
26.3
9.1
10.7
6,2
25.4
67.9
86.8
29.3
92,0
27.9
66.4
19.3
77.4
57,6
92,3
29.7
59,9
13,3
69,5
DAYS
Sludge wasted and lost (1)
(kgVSS/day)
3
16-30 May 90
FMCT
CONV
S.S. (kg)
20.9
45.5
13.9
216.9
10.4
21.7
0.0
12.9
34.1
95,4
3.7
129,3
2.7
145.7
Total(kg)
36.6
132.2
43.3
310.9
36.3
108.1
19.3
90.3
91.7
187,6
33,4
189,2
16.0
215.2
46.6
50.2
39.6
76.9
27.4
64.2
21.6
69.5
46,1
97,2
52,9
51.1
14.9
67.0
Sludge mass 0 A.S. (kg)
S.S. (kg)
23.3
0.6
23.0
134,2
18.5
28.1
0.0
8.1
6.9
45,2
13,8
111.8
3.9
141.5
Total(kg)
69.9
50.9
62.6
211.1
45.9
112.3
21.6
77.6
55,0
142.4
66.7
162,9
18.8
208.5
Sludge mass balance (kg) (2)
113.9
111.6
230.1
159.6
149.7
61.1
8.9
42.6
109.6
125.4
75.3
71.3
71.9
296.2
Total removed BODS (kg)
203.1
226.2
435.1
439.4
299.1
269.7
57.4
161,1
303.6
395.2
164.6
192,0
117.8
462,0
0.56
0.49
0.53
0.36
0.50
0.23
0,15
0.26
0.36
0.32
0.46
0,37
0,61
0,61
Observed Yield (kgVSS/kg BOD5) (3)
(1)
Sludge wasted and lost - (Ow.Xa) + (O-Ow).VSSe
(2)
Sludge mass balance - (Sludge mass 1) • (Sludge mass 0) + (Sludge wasted and lost N 8 days)
(3)
A.S.:
S.S.:
0 :
1:
Observed Yield - sludge mass balance / total removed B0D5
Activated sludge
Secondary settler
Beginning of period
End of period
or
TABLE 5.13: SLUDGE QUALITY
PERIOD
DATE
1
2
16-29 Jan 90 26Feb-26Mar 90
FMCT
CONV
FMCT CONV
SVI (ml/g)
Senang Velocity ( m / h )
Blanket level (m)
3
16-30 May 90
CONV
FMCT
4
9-24 Jul 90
CONV
FMCT
5
20Aug-3Sep 90
CONV
FMCT
6
14-31 Jan 91
CONV
FMCT
7
18Feb-8Mar91
CONV
FMCT
104
119
273
140
299
99
51
65
44
41
143
167
426
107
1.32
0.9
0,35
0.06
0.66
0.36
4,3
1.7
3.4
1.8
0.7
0.2
0.7
0.6
2.1
1.4
2.5
3.1
2.9
1.6
No detec
1,3
1.5
1.7
1.8
2.9
1.6
3.3
4
3
4
4
3
2
2
3
3
♦
4
1
1
2
♦
-
4
-
-
Filamentous M i c r o o r g a n i s m s
(Relative abundance)
Nocardia
S. natans
T.1701
H. hydrossls
T.1663
T.0041
1
2
Fungi
Zooglea
+
-
3
-
1
♦
-
2
-
-
+
-
-
1
1
+
-
+
♦
+
+
-
+
-
1
+
-
-
-
-
++
+♦
-
M L S S (mg/l)
3177
4476
2749
6714
1735
6671
1395
4927
4186
7718
3585
5073
887
5527
MLVSS (mg/l)
2642
3630
2194
5091
1420
5009
1097
3708
3138
5606
2346
3087
650
3618
NOTE1
NOTE 2
Relative Abundance of M i c r o o r g a n i s m s (by E ikelboom)
Zooglea++ : very a b u n d a n t
*
-
Sporadic g r o w t h of filamentous microorganisms
1 L o w g r o w t h of filamentous m i c r o o r g a n i s m s
NOTE3
2 M o d e r a t e g r o w t h of filamentous microorganisms
Settling velocity depends on M L S S concentration
3 High g r o w t h of filamentous microorganisms
4 E xcesive g r o w t h of filamentous microorganisms
5
Field o l v i e w f u l lof filamentous microorganisms
CJ1
00
TABLE 5.14: METALS IN PRIMARY SLUDGE
PERIOD
DATE
Ca (mg/kg dry sludge)
CSP7/UPS7
1
31 January 90
CONV
FMCT
2
14 March 90
CONV
FMCT
29033
32597
41609
41339
40444
26666
26480
25489
3
30 May 90
CONV
FMCT
4
5
25 July 90 4 September 90
FMCT
CONV
FMCT CONV
6
1 - 4 Feb 91
CONV
FMCT
7
8 March 91
CONV
FMCT
Mg
1750
2535
3674
3246
5227
4675
4516
1983
Cd
3,2
3.6
4
5.9
1.9
2
5.6
5.3
Cr
127
326
55,6
57,1
27.6
113
133
136
Cu
565
257
179
175
152
244
460
492
Ft
77156
141163
73168
71260
34819
130746
179325
192094
Mn
372
525
371
378
203
282
1162
1245
997
1057
NI
587
154
127
120
90.7
143
Pb
99
168
218
217
159
91,5
160
154
Zn
496
733
663
644
471
539
962
1018
Hg
ND
NO
1.32
0.79
0.67
0.42
0.12
0.25
SS (mg/t)
13180
14660
35906
36876
30552
16000
31044
12052
VSS(mg/l)
9700
9937
15752
5980
9019
22836
22S76
20783
CJI
co
TABLE 5.15: METALS IN ACTIVATED SLUDGE
PERIOD
DATE
Ca (mg/Kg dry sludge)
1
31 January 90
CONV
FMCT
CSP2/USP2
2
14 March 90
CONV
FMCT
3
30 May 90
CONV
FMCT
5
4
25 July 90 4 September 90
CONV
FMCT
CONV
FMCT
6
1 - 4 Feb 91
CONV
FMCT
7
8 March 91
CONV
FMCT
14052
11367
17915
22972
28098
20067
15113
13781
23894
23019
27733
28759
18337
22303
Mg
2213
221B
2932
2948
3549
3559
4220
4064
2962
3302
4489
6291
3906
5100
Cd
2.2
5.5
2.2
4.1
3
5.9
3.9
5.3
3.9
3.9
5.9
4
6,4
8.3
Cr
77.5
83.2
126
679
82.6
142
70.7
74.2
43.4
46.6
35.9
43,9
25.8
38,3
Cu
232
302
219
360
157
204
347
346
182
183
223
219
75.5
170
F«
32197
36180
35940
50823
18338
36576
69971
73852
62796
68376
55466
62706
332S2
35507
Mn
177
175
224
335
139
214
296
244
434
377
295
393
195
268
NI
166
163
165
218
148
190
214
249
168
177
189
173
66
91
Pb
117
125
124
157
160
182
236
228
146
153
143
173
126
146
Zn
549
571
569
874
704
1018
983
682
551
596
63S
663
460
548
Hg
ND
NO
NO
NO
ND
NO
2.1
3,1
0.49
1,31
1.11
1.06
0.68
0,79
SS (mg/t)
4925
6333
3198
7858
1934
6460
1846
3218
5344
8380
2377
5334
958
5456
VSS(mg/l)
4143
5348
2572
5882
1584
4S66
1338
2512
3744
5648
1657
3472
766
3816
O!
O
TABLE 5.16: AERATION PARAMETERS
PERIOD
DATE
2
1
16-29 Jan 90 26Feb-26Mar 90
FMCT
CONV
FMCT CONV
3
16-30 May 90
FMCT
CONV
4
9-24 Jul 90
CONV
FMCT
5
20Aug-3Sep 90
CONV
FMCT
6
14-31 Jan 91
CONV
FMCT
7
18Feb-8Mar 91
CONV
FMCT
12.9
13,2
15,6
16,4
19,3
19.7
23.7
23,7
22.7
22.6
6.4
8.3
8.4
8.2
Specific OUR (motygVSS.h)
19,62
19,56
12,35
9,92
19,35
15,61
13.64
12.35
22,77
19,50
6,38
11.04
22,1
19.11
OUR (mgOa/Lh)
56,72
70.48
26,9
43,66
29.11
79.7
16
53.3
69
109,7
17,42
39,66
19.34
83.84
0.97
2.65
1.6
2,07
1,64
1.56
1,53
2.5
1.4
1.4
1,63
2,65
1.93
2.51
69
93,2
46
55
67
100.6
32
63.5
96.5
118.8
33
37,4
30
63
Temperature (deg C)
D.O. (mgOj/l)
Air Flow (m'/h)
Relation Air Flow C/F
0.74
Energy In Aeration (kw.h)
1393
Relation of Energy In Aeration
CVF
1.23
C/F-
CONV Une Value
FMCI Une Value
OUR - Oxygen Uptake Rate
0,64
1126
765
0,91
045
465
0.58
0.81
0.50
0.67
796
256
0.51
500
768
0,63
0.88
922
301
0.66
0,48
349
301
0.46
660
TABLE 5.17: ENERGY CONSUMPTION
PERIOD
DATE
Energy In Recirculation pumps (kw.h)
2
1
16-29 Jan 90 26Feb-26Mar 90
FMCT
CONV
FMCT
CONV
3
16-30 May 90
CONV
FMCT
76
62
146
129
75
3S3
4
9-24 Jul 90
CONV
FMCT
5
20Aug-3Sep 90
CONV
FMCT
6
14-31 Jan 91
CONV
FMCT
7
18Feb-8Mar91
FMCT
CONV
114
300
66
1S3
77
70
68
142
301
349
301
660
Energy In Blowers (kw.h)
1393
1126
765
S4S
465
799
256
500
768
922
Total Energy (Kw.h)
1469
1190
913
974
540
1151
370
600
854
1075
378
419
369
602
CD (mVh)
2.53
2.54
2.07
2
2.5
2.3
1.51
3.44
5.9
6.2
2.56
3.14
1.76
6.58
N«days
Flow Treated (m1)
Energy Consumption Total (kw.h/m*)
Energy Consumption In areatlon (kw.h/m*)
14
14
29
29
15
15
16
16
15
15
18
18
19
19
650.06
S53.4
1440,72
1392
900
626
579.8
1320.9
2124
2952
1105.92
1356.48
811.66
3000.48
1.73
1,40
0.63
0.70
0.60
1.39
0.64
0.61
0,40
0,36
0.34
0.31
0.4S
0.27
0,31
0.27
0.25
0,37
0.22
1.64
1.32
0.53
0.60
0.51
0.96
0.44
0.36
0,36
B005 Removed (kg)
203.1
226,2
435.1
439.4
299.1
269,7
57.4
161.1
303,6
395,2
164.6
192.0
117.6
462.0
B005 Removed (kg/day)
14,51
16.3
15,0
15.15
19.93
17,96
3.58
10.06
20,23
26,34
9.14
10.66
6.20
2S.36
7.23
5,22
2,10
2.22
1.61
4.27
6.45
4.97
2.B1
2.72
2.30
2.16
3.13
1.66
2.96
4.45
3.10
2.S3
2.33
1.63
1.61
2JJ
1.37
Energy Consumption Total
(kw.h/kgBCO)
Energy Consumption (kw.h alratlon/kg BOO)
Air Consumption (m'/day)
m* alr/kg BOO removed
6.66
4,94
1.76
1.92
1.5S
1.656
2.237
1.104
1.320
1.608
2.414
766
1.524
2.316
2.651
792
896
720
1.512
114.13
137.24
73.6
67.13
60.66
134.26
214.5
151.49
114.46
108.24
86.65
84.24
116,13
59.62
Note: In period 1 atr diffusera were clogged and were replaced for new ones In period 2. So that the Energy consumption In blowers In period 1 is much higher than In other periods.
TABLE 5.18 : SLUDGE AGE CALCULATION
PERIOD
DATE
2
1
16-29 Jan 90 26Feb-26Mar 90
CONV
FMCT
CONV
FMCT
Temperatur« (*C]
3
16-30 May 90
CONV
FMCT
4
5
9-24 Jul 90 20Aug-30Sep 90
CONV
FMCT
FMCT
CONV
6
14-31 Jan 91
FMCT
CONV
7
18Feb-8Mar 91
FMCT
CONV
12.9
13.2
15,6
16.4
19.3
19.7
23,7
23.7
22.7
22.6
6,4
6.3
6,4
6.2
14
14
29
29
15
15
16
16
15
15
16
1B
19
19
Fexcese (kg VSS/day)
6.79
2.16
6.60
2.06
10.49
4.35
0.70
1,66
4.67
5,34
6,03
2.50
3.93
15,24
Mxl (kg)
60.8
132,2
43.3
310.9
36.3
106.1
19,3
90,3
91.7
167.6
33,4
169,2
16.0
215.2
MxO(kg)
69.9
50.9
62.6
211.1
45.9
112.3
21.6
77,6
55,0
142,4
66.7
162.9
16.6
206.5
1.3
9.6
-0.7
3.4
-0,5
-0.3
-0.1
0,6
2,4
3,0
-1.9
1.5
-0.1
0.4
Ntdays
(MX1-MMO)/N (kg/day)
79.4
91,6
53.0
261.0
42,1
110.2
20.5
64,0
73.4
165,1
50.1
176,1
17,4
211.9
[(Mx1-MxO)/N]»Fexce>s (kg/day)
6.1
6.0
7.9
5.5
10,0
4.1
0.6
2,7
7,3
6,4
4.2
4,0
3,6
15,6
Total aludge age (days) (1)
9.6
11.5
6.7
47.4
4.2
27.1
36.6
31.4
10.0
19.7
12.0
44.4
4,6
13.6
47.6
65.3
39.4
91.6
25.6
90,2
19.6
66.7
56.5
100,9
42.2
5S.6
11.7
65.1
5.6
6.2
5.0
16.7
2.6
22,1
35.5
25.0
7.7
12,1
10,1
14.0
3.1
4.2
43.0
25.6
58.7
61 J)
46.4
5.2
0.5
O.S
6.0
2,6
25.7
25.6
23.2
24.7
(MK1«MXO)/2 (kg)
Va.Xa (kg)
Aerobic sludge age (day«) (2)
N-NH3 In effluent (mg/l)
(1)
Total sludge age (days) -
(Mx1+Mx01/2
[(Mx1-Mxü)/NJ+(-excess
(2)
Aerobic sludge age (days) -
Vo.Xfl
L(Mx1-MxÚ)7NJ+t-excess
Fexcess -
Sludge wasted and lost (kgVSS/d)
Mx1 -
Total sludge mass (kg) end of period
MxO-
Total sludge mass (kg) beginning of period
((Mx .•Mx0)/N]+Fexcess -
Sludge acumutated En the system (kg/day) + sludge wasted and lost (kg/day)
VauXa -
Average sludge mass In alratlon tank (kg)
O)
-646 MODELLING
6.1 Introduction
To verify and analyze the obtained experimental data against the known theory, a
computer program CAB (Consorcio de Aguas, Bilbao) was developed. The program
includes current theory for activated sludge reactors and clarifiers, and is therefore a
valuable tool which can be used in understanding and interpreting measured data.
This chapter shortly describes the implemented mathematical models, the model set
up of the plant and the results obtained from calculations with the program.
6.2 Concepts and models
The process model used in CAB is based on the IAWPRC Activated Sludge Model
No 1. (Henze et al, 1987), and for the secondary clarifiers on the flux theory adapted
for modelling with the activated sludge models (Dupont, 1991).
6.2.1 Activated sludge model
The model for activated sludge is presented in figure 6.1. Explanations of the
components and constants are found in the symbol list at the end of the chapter. The
model is a slightly expanded version of the original Activated Sludge Model No. 1
(Henze et al, 1987).
To prevent numerical problems for components in the model which have a negative
stoichiometric constant, a few new terms are added to some of the processes. Finally,
three new components (Particulate precipitated compounds Xpg, Particulate
orthophosphate XPO, soluble phosphate SP0) and three new processes (process 10,11
and 17) are added to deal with simultaneous precipitation.
A general description of the included components and processes can be found in
numerous papers (Henze et al, 1989; Gujer, 1991).
Component -
Process I
12
*BH
Xpo
XBA
13
14
17
Process rates
ML"J-Tn
Spo
1 Aerobic growth
Y„-1
of heterotrophic
°NH
IV
°AIK
^ H ^ S R K Q H ^ O ^NH^NH ^AH^AIK
2 Anoxic growth
-1*Y H
of heterotrophic
1-Yu
f,
S
*OH
MH-
2,86-YH
KSH^SR
KOH'SO
K
N
NOH' , S NO K N H ^ N H
KAH'SAU
3 decay of
heterotrophic
1-f.
U-l. -
"H-*BH
4 Aerobic growth
of autotrophic
^"YT
->nb
1
YA-4.5
KA-
So
KNA^NH
KOA*SQ
KAA^ALK
•XBA
5 Decay of
autotrophic
1-f.
B
A-XBA
6 Hydrolysis of
KHX-
Particulate
Xs-
(1Æ2H)-XBH
7 Hydrolysis of slowly
degradable
^HS'SŞŞ'XBH
8 Hydrolysis of
particulate organic
•nu
,e.
9 Ammonification.
^HND-^— 'fO)
14
10 Iron oxidation.
-2
3ï
11 Precipitation.
2_
31
J6
T
Ket' S 0 -
-• S n
KAO^ALK
*ME ^PO *FE
12 Resolubilisation.
-2
31
Figure 6.1 Activated sludge model matrix.
Kpo'
05
oí
-666.2.2 Secondary clarifier model
The model for the secondary clarifier is based on the zone settling theory for sedimentation in clarifiers described among others by Vesilind, 1979, and Ekama et al, 1984, and
adopted for use with activated sludge models by Dupont, 1991.
The conceptual idea by the implemented
secondary clarifier is shown in figure 6.2.
The clarifier is regarded as a flat bottom
cylindrical tank with a given height and a
given area, in which an inlet is placed in
a given depth, from which there is an
upward flow and a downward flow. These
flows together with the gravity settling of
the particles gives the flux expressions for
the upper an lower part of the clarifier.
Total flux expression :
GT = Gt + GF = V¿Xs * VpXs (6.1)
: Total flux
Gravity flux
: Flow flux
Vg : Settling Velocity
Xss: Sludge concentration.
VF : Flow velocity
Figure 62 Conceptual model for clarifier.
Expression for flow velocity:
V =
^F =
—
A
ÖR + ßp
for h > h .„,
(6.2)
for h < h inlet
A : Area of clarifier
h : Height of clarifier
Q E : Effluent flow
QR : Return sludge flow
Qp : Waste sludge flow
67
Expression for settling velocity:
(63)
-h-Xs
Vt = V0- e
V0 : Max settling velocity due to gravity
k : Sludge quality constant
Inserting expression 6.2 and 6.3 in the total flux expression 6.1 the following expressions
for flux in the upper and lower part of the clarifier are obtained:
Gj. =
~Ã J
{ °
■Xs
for h > h jnJet
2 p ' • J£¡
GT =
for h < h
(6.4)
(6.5)
To be able to model the sludge which does not settle in the clarifier, the following
empirical model is used for suspended solids in the inlet to the clarifier.
'NO,
-^NS
=
-^lnit
+
-*^N03
(6.6)
^N03 + ^N03
Y
NS
xs,Init
xs,N03
^N03
: Non settled suspended solids in inlet to clarifier which will not settle
: Floating particles in the inlet to the clarifier.
: Max concentration of suspended solids due to nitrate in the inlet to the
clarifier, which will not settle.
: Monod constant for nitrate.
: Concentration of nitrate in the inlet to the clarifier.
Applying model 6.4, 6.5 and 6.6 to mass balances over tiny elements of layers in the
clarifier, the concentration profile in the clarifier can continuously be calculated over
time by integration.
-68-
6.3 CAB description
CAB (Consorcio de Aguas, Bilbao) is a dynamic simulation program developed for this
project. The purpose of the program has been to develop a program which could be used
as an analyzing tool and which could support the work of verifying and analyzing the
experimental data. In the development of the program special attention is paid to the
clarifier part, because the differences in clarifier design is a key factor in the difference
of the two pilot plant lines.
One of the goals for the program was that it should be possible to run the program on
any PC type computer. This has been achieved, but reasonable minimum hardware
requirements would be PC with a 286 processor, a mathematical co-processor and a
graphic screen.
Plant
Operatio
Constants
-CAB Version 1.0Presentation System utilities
Exit
Plant
Table of plants
Flow scheme
Ctrl-T
Dimensions
Dimensions
Volume of Activ, sludge 1
Surface aeration (Kla) for Activ, sludge 1
1 8 0 ra 3
1 0 1/d
Surface area of Final sed. 1
Height of Final sed. 1
Position of inlet in Final sed. 1 •
1 2 5 m3
4 4 m
1 3 m
Plant: USP
Const:
Input tank volumes
<F1> Help
<F10> Save
Influent:
RAH Max :
213016 Avail:
213008 bytes
Figure 63 Example on user interface from CAB.
The program is driven by pull down menus (Figure 6.3), from where the different tasks
can be operated. This includes :
- Possibilities for setting up the configuration and dimensions of the plant.
- Possibilities for operating the designed plant with different controls and operating
strategies.
- Possibility to simulate dynamic load conditions.
- Possibility for calibrating the model by adjusting model constants.
- Graphic and table output of calculation results
69
The program and manual for the program can be found in annex 6.
6.4 Model Plant
For model purposes a simplified flow sheet of the plant was set up (Figure 6.4). Due
to the fact that both lines have the same flow sheet (but different dimensions), only the
flow sheet for one pilot plant line is drawn. The actual plants includes a primary clarifier,
but this is not included here because CAB do not include a model for the primary
clarifier.
The figures (SPx) on the flow sheet
are the measuring points, where
SP2
samples where taken.
The effluent pipe (SP6) from the
bottom of the clarifier in the flow
sheet is only used for sample-taking
and not for control of sludge mass
and sludge age. The actual sludge
SPI .
3
V
.i—iM
AS
/i
«* SlrD
wasting is handled by the pipe from Figure 6.4 Pilot plant flow sheet used for
the activated sludge reactor (SP2). modelling
In table 6.1 the physical dimensions of the pilot plant used for modelling is listed. In the
table is given an actual inlet height, and a used inlet height. A lower height is used in
the modelling, as it is not possible to model a sludge blanket height which is below the
actual inlet height with the present one dimensional flux model. The only consequence
of this is that the retention time for both water and biomass in the clarifier might be
longer, giving a larger delay and damping in the clarifier than expected.
70CONV
FMCr
3
Volume of Activated sludge reactor
18 m
18 m3
Area of secondary clarifier
3.8 m2
12.5 m2
4m
4.5 m
Actual
2m
2.4 m
Used
1.2 m
1.3 m
Height of secondary clarifier
Depth of inlet in secondary clarifier
Table 6.1 Dimension of the CONV and the FMCT line of the pilot plant.
It is further seen that the volume of the clarifier at the FMCT line is much greater than
the volume of the clarifier in the conventional line. This is the key difference between
the two lines in the plant.
6.5 Input data handling
The data which are obtained from the pilot plant are very comprehensive and cover a
long period of intensive measurements of many parameters. From these data 4 periods
were selected for further modelling, covering the last 4 periods of intensive measurement.
The raw data as they are used for modelling are listed in Annexes 7.1 to 7.4. Hatched
fields in the tables are fields that contain estimated data.
Three reasons make it necessary to check the data and make some corrections and
calculations before they can be input to the model :
- The model is not able to handle data in the inlet which is inconsistent regarding to
mass balances. The influent measurements must be checked for mass balance
inconsistency, and eventually new values must be extrapolated if inconsistency is found.
- To avoid missing data it is necessary to estimate values in cases where no measuring
was conducted.
- As the model internally deals with model components, all of which it are not possible
to be measured at present, it is necessary to estimate values for these components by
conversion of the measured influent data. This conversion must be conducted both for
inlet data, and for output data, converting model data back to measurable data.
-71 In the two first cases above the estimation of data is best done before the data are entered
into the program. In the last case the conversion of the measured data is done entirely by the
program. The user can control this conversion by means of conversion constants given to the
program (Table 6.2).
CONV
FMCT
CONV
FMCT
COEV!oluhl./CODIotlll
0.42S
0383
5%H/^particulate
0.99S
0.995
Bor^olubl./BODrot.i.
0.422
0.410
0.005
0.005
BOD/BOPrnfinit.
0.6
0.6
'%A/B0I}?«rticiiLt.
}%/BODpartlculat.
0.900
0.900
BOD!n£lnlt./COD
0.729
0.696
%s/cor% o l u b l .
0.5
OS
Kj-hfeojjifcx./Kj-Nrotal
0.835
0312
%R/ C O E %olubl.
OS
OS
NIVN/KJ-NÎO1U1J1.
0.882
0384
PCVP/Frot«!
0.637
0.642
Constant
Constant
Table 62 Conversion constants used for the inlet.
The conversion constants are based on mean values for all the measured data of the 4 periods. The
conversion constants are regarded as being identical in the 4 periods.
The variations patterns for total COD and total Kjeldhal-N of the influent from the 4 periods are
shown in figure 6.5 to 6.8. There is no significant difference in the influent variation of the two lines.
Figure 6.5 Influent patterns of total COD
Figure 6.6 Influent patterns of total COD
and total Kjeldhal-N from period 4
and total Kjeldhal-N from period 5
72
Figure 6.7 Influent patterns of total COD
Figure 6.8 Influent patterns of total COD
and total Kjeldhal-N from period 6
and total Kjeldhal-N from period 7
6.6 Operation conditions used for modelling
CONV6
FMCT6
CONV7
FMCT7
Units
CONV4
FMCT4
CONV5
FMCT5
Oxygen
13
23
13
1.8S
1.7
2.75
13
23
mg/l
Inlet flow
13
3.4
6
&2
VAR1'
VAR1'
VAR1'
VAR1'
m 3 /h
Return flow
3
9
13
VAR3)
50%
50%
50%
50%
ni/h
Waste flow
0
0
0
0
VAR2)
VARZ)
VAR2'
VAR2'
m 3 /h
Temperature
20
20
22.8
218
113
8.6
8.2
8.2
oC
Parameter
Notes :
1) The inlet flow is variable, but controlled to keep the F/M ratio constant
2) The waste flow is variable, controlled by the sludge blanket
3) During period 5 the return sludge flow in the FMCT line decreased from 8.2 to 2 3 m /h
Table 6.3 Operation conditions for modelling
Table 6.3 shows the operation conditions as they are used under the simulation, and in most cases
these are the same operation conditions as used in the pilot plants.
-73-
6.7 Modelling and analyzing
In this work, analyzing the experimental data is conducted as calibrations on each of the 4 periods
and in the two plants. In this way it is possible to find out whether there is any deviation from
expected behaviour of the plant. This could either be of the plant in general or for a single period.
If there is found any deviations then the program is valuable tool to use, helping to explain the cause
of the deviation.
6.7.1 Notes on modelling
The retention time and damping of the effluent concentrations from the clarifier is greater than
expected. This due to the fact that the actual used inlet by the modelling is lower than the physical
inlet depth of the clarifier. This is the only way to model sludge blanket dynamics with a one
dimensional clarifier model, when the measured sludge blanket is below the physical inlet of the
clarifier (see operating conditions table 6.3).
The modelling of period 4 for the conventional line is a special case of the case above and gives
some problems in form of a very low or non existing sludge blanket. To model the concentration,
the sludge age and the height of the sludge blanket in this period, it was necessary to model the
clarifier with a inlet in the lowest possible level (in this case 0.2 m). This gives as explained above
a greater retention time in the clarifier.
During the calibrations it was assumed that the plant during the intensive periods was not in a
transition period. This gives the advantage that the same period can be run over and over. This is
very difficult to handle in period 4 and 5, because of the very low sludge wasting, which made the
sludge mass in the system slowly, but continuously increasing. This in turn reflects that the system
might not be totally in balance.
-74-
BODinfinity/BOD
CONV4
FMCT4
C0NV5
FMCT5
CONV 6
FMCT6
CONV 7
FMCT7
1.667
1.667
1.667
1.667
1.667
1.667
1.667
1.667
Uniu
0.71
0.77
0.75
0.64
0.76
0.7
0.7
0.71
jBOO/sCOO
0.7
0.8
0.7$
SBOO/gCOO
eBOO/sBOD
BOD/CODtotal
Effluent
0.85
0.6S
0.7S
0.64
OS
Effluent
0.6
0.6
0.7
0.61
0.7
0.64
0.66
0.69
SSS/tCOO
Clarifier
0-5
0.6
0.7
0.61
0.7
0.6
0.6
OS
sss/scoo
Qarìfìcr
SS/CODrot.1
Table 6.4 Conversion constants used for effluent and secondary clarifier
In table 6.4 are listed conversion constants for the effluent and for the secondary clarifier .
The values for the effluent are mean values calculated form the measured data for each period.
The values for the secondary clarifier were found by calibration.
The conversion constants are mainly used for converting the measured influent components
to the components used by the model, and for converting the model components to measurable
components which can be compared with the respective measured values. The secondary
clarifier makes an very important exception to this. In the secondary clarifier, the three
constants which convert particulate model components of COD, particulate iron, and
precipitated phosphorus compounds to SS are used to calculate the sedimentation rate of the
particulate components. When calibrating a model it is very important to be aware of this, as
it can change the mass of suspended solids in the clarifier and thereby have an impact on the
sludge age and sludge blanket height
During the modelling, one of the objectives has been to calibrate the constants and the
operation so that the calculated sludge blanket and sludge age are matching the sludge blanket
height and sludge age obtained during the experiments. In this way the sludge blanket and the
sludge age become operating parameters.
6.7.2 Some results from the modelling of the pilot plant
In this paragraph are described some of the key results from the modelling, and a few
representative curves are shown with comments.
75-
Table 6.5 shows mean values of some key results from the calibration. As it can be seen the
modelling results are comparable with the results obtained from the measured data.
CONV6
FMCT6
CONV7
FMCT7
1.72
1.8
1.7
1.8
2.9
1.8
33
m
2.9
2.0
33
m
10
19.7
12
44.4
4.6
13.6
days
36
10
25
14
50
15
9
days
35.5
25
34
24
7.7
12.1
10.1
14
3.1
42
days
8
13
10
14
3
3
days
Measured
16.0
Calculated
21
533
69.0
109.7
17.4
39.7
193
63.6
46
75
83
18.8
21
125
355
CONV4
FMCT4
CONV5
FMCT5
Measured
-
1.4
1.4
Calculated
0.2
1.4
1.4
Measured
36.8
31.4
Calculated
35
Measured
Calculated
Parameter
Uniu
Sludge blanket
Total sludge age
Aerobic sludge age
OUR
Table 6.5 Key results from modelling. Mean values.
jtf
Figure 6.9 COD total from Conventional
Figure 6.10 COD soluble from Conven-
line, period 5.
tional line, period 5
Figure 6.9 and 6.10 show the modelling results from the conventional line, period 5, of total
COD and soluble COD. The modelling results for COD correlate with the measured values
quite well. For soluble COD the calculated values tends to give higher values than the
measured ones. This is probably caused by soluble inert COD from the influent. The soluble
inert COD in the influent tends to be estimated to high with the currently used methods
(Soluble inert COD = soluble COD - soluble BODinfinite).
76-
Figure 6.11 and 6.12 shows BOD total and BOD soluble from the FMCT line in period 7.
The general trend for these results is that the calculated mean concentration for total BOD
match the measured values very well, but the dynamics is missing in the calculations. The
calculation generally estimates the Soluble BOD concentration to high. This could possibly be
corrected by lowering the Monod constant for soluble substrate in the growth process for
heterotrophic bacteria (See paragraph 6.7.3).
Figure 6.11 BOD total from FMCT line,
Figure 6.12 BOD soluble from FMCT
period 7
line, period 7
±=
il 111 9
Figure 6.13 SS concentration in CONV
Figure 6.14 Alkalinity from Conventional
line, Period 7
line, period 6
Figure 6.13 shows the concentration of suspended solids in period 7 of the Conventional line.
In the shown figure the suspended solid concentration matches the measured values very well,
but in general the calculated curves are less dynamic than the measured values. Figure 6.14
shows the alkalinity from Conventional line period 6. Except for period 4 the calculated
alkalinity concentration correlates with the measured values very well.
-77-
Figure 6.15 and 6.16 shows total Kjeldhal-N and Ammonia/Nitrate curves from Conventional
line period 4. By the modelling total Kjeldhal-N is often predicted to be lower than the
measured concentration. For ammonia and nitrate the modelling gives results which matches
the measured values (See comments on the hydrolysis constants KHX and KHND in the next
paragraph).
Figure 6.15 Total Kjeldhal-N from Con-
Figure 6.16 Ammonia and Nitrate from
ventional line, period 4
Conventional line, period 4
6.7.3 Calibration of constants in the model
By the calibration the main points for focus is one hand the constants related to the secondary clarifier controlling the effluent quality, the concentrations of suspended solids in the
process tanks, the sludge age, and the sludge blanket height. On the other hand the constants
related to the activated sludge processes controlling the concentration of COD and the nitrogen components in the process tanks.
-78
Default
CONV4
FMCT4
CONV5
FMCT5
CONV6
FMCT6
CONV7
FMCT7
Unit
(.1
0.06
0.005
0.005
0.005
0.005
0.005
0.005
0.005
0.005
gN/gCOO
I%H
20
IS
25
25
2-5
IS
Z5
25
IS
gCOO/m 3
•%X
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
m3/gCOOAl
•%HD
0.25
025
0.25
0.25
0.25
0.25
0.25
0.25
0.25
T«03
0.098
0.103
0.103
0.103
0.103
0.103
0.103
0.103
0.103
KiiA
1
1.0
0.25
1.0
0.25
1.0
0.25
1.0
0.25
gN/m3
m/d
Constant
V0
137
130
130
130
130
160
150
170
150
k
037
0.75
0.65
02
OJ
0.8
0.75
11
0.6
m 3 AQ
SSlnit
5
S
S
10
10
5
6
5
6
g SS/m 3
S%03
25
10
10
20
20
20
20
20
20
gN/m3
Table 6.6 Constants found by calibration of the Pilot Plant
In table 6.6 are listed the default constants of the model together with constants which were
changed during the calibration. The default values of other constants of the model can be
found in the symbol list. Only a few of the constants in the model were changed. Most of the
changes are small and kept within normal limits of variation. In the following is a short description of the changes and there implications.
Comments to constants regarding activated sludge processes.
fM : Fraction of nitrogen in inert material. This constant is changed to a very low value, to
meet the requirements of the nitrogen mass balance of the influent wastewater. If this value
was greater there would be a much greater need for estimation of some of the measured values
in the influent.
KsH : Monod constant for substrate of heterotrophic bacteria. As it was not possible with the
default constant to match the measured values of soluble BOD, this constant is changed to a
lower value. As seen in figure 6.7 this value might even be lower than the calibration value
of 2.5 g/m3. Experience has shown that it is often necessary to decrease this Monod constant
to get the desired results. Therefore it can not be regarded as being a special feature of the
Bilbao waste water.
-79-
Krøj and KHND : Hydrolysis rate for COD, and hydrolysis rate for nitrogen. These constants
are estimated to be lower than the default values. With the default values of this constants the
particulate Kjeldahl nitrogen in some of the periods is calculated to be lower then the
measured values. The low values estimated by the calibration compensate somewhat for this
(Figure 6.8) as it increases the amount of particulate degradable COD and the nitrogen bound
in organic substrate. As the theoretical value of these constants is nearly unknown, it can not
be concluded from this that these constants are a consequence of unusual wastewater in Bilbao.
T N03 : Temperature coefficient for nitrification. The value are slightly changed, compared to
the default value, to obtain a greater dependency of the nitrification on temperature. This is
done to achieve a lower nitrification at low temperatures. By the modelling this accounts for
all the differences in the nitrification rates in the four periods. But one must be aware that the
measurements show that there is a rather low alkalinity in the wastewater, and this could give
a reason for reduced nitrification under certain circumstances. This situation could not be
observed by the modelling as there is no inhibition of nitrification by low pH included in the
model.
Comments on constants regarding secondary clarifier performance.
V„, k One of the more interesting changes witch is made affects the constants for calculating
the sludge settling velocity (The Maximum settling velocity V0 and the sludge characteristic
constant k). These constants reflects the settling properties of the sludge. In general it is not
possible to estimate a general value for these constants, because they are very dependent on
the actual settling performance of the sludge which in turn is dependent on temperature,
reactor configuration, bacterial composition, influent composition etc. The constants Vo and
k is very important for the calibration of the sludge blanket height and the sludge age.
From figure 7.7 it is seen that the maximum settling rate can be determinate from the
expression:
ln(V0) = 2 *
V0 = 170 m/d
Comparing this value to the calculated values in table 6.7 it is seen that the calculated values
in general are lower. However comparing the dynamics of the calculated sludge blanket with
the measured sludge blanket it was observed that the dynamics of the sludge blanket height
of the modelling was more dynamic than the measured value. Taking this in account the values
from the calibration is not contradictory to values above.
-80
The k value reflect the sludge volume in the clarifier, and it is possible to compare the k
value with the measured sludge volume index. Figure 6.17 shows the estimated k value as
function of the measured SVI values of table 13. As it can be observed this correlate reasonably good.
As the k value reflects settling properties of the
clarifier it can be deduced that at high temperatures as in period 4, and especially in period 5,
there was a very good settling. I contrary to this,
the settling in period 6 and 7 at the low temperature was very poor. This is especially true for the
conventional line in period 7.
Figure 6.17 Estimated k values as function of measured SVI
6.8 Conclusion
The program has shown to be a valuable tool for
analyzing data. The program can tell whether there is any reason for concern, regarding the
composition of a certain waste water, and it can give some indication of the consequences on
the effluent quality and the operation of the plant with this waste water. Further it can be
helpful in explaining measured results.
From the work with the program it can be
concluded that the calibration of the model can be conducted without serious change of
constant values. This indicates that there is nothing which indicates that the investigated waste
water of Bilbao has a special composition. One must keep in mind that this conclusion is valid
inside the limitations of the model. The measurements (See chapter 7) has revealed that there
might be problems with nitrification because of low alkalinity.
However the calibration of the constants regarding the secondary settler, indicates that a
configuration of the waste water treatment plant similar to the pilot plant could favour bulking
tendencies in the plant, especially at low temperatures.
-81
6.9 List of symbols
Components in activated sludge model CUnit g/m3)
V
BH
Xs
X,
x,ND
M>0
°NH
SND
^NO
Spo
^ALK
So
SFE
S,
Heterotrophic bacteria
Autotrophic bacteria
Particulate degradable organic COD
Particulate inert organic COD
Particulate precipitated iron
Particulate degradable organic nitrogen
Particulate orthophosphate
Soluble slowly degradable substrate COD
Soluble easily degradable substrate COD
Ammonium
Soluble degradable organic nitrogen
Nitrate
Orthophosphate
Alkalinity
Oxygen
Soluble iron
Soluble inert organic COD
g COD/m3
g COD/m3
g COD/m3
g COD/m3
g Fe 3+ /m 3
gN/m 3
g FeP0 4 /m 3
g COD/m3
g COD/m3
gN/m 3
gN/m 3
gN/m 3
gP/m 3
g HCOVm3
g COD/m3
g Fe 2+ /m 3
g COD/m3
Stoichiometric constants in activated sludge model
default value
Constant
0.67
YH
: Heterotrophic yield
Autotrophic yield
0.24
Nitrogen in bacteria
0.086
Nitrogen in inert substrate
0.06
Fraction of endogenous day
0.08
Kinetic constants of heterotrophs in activated sludge model
Constant
default value
: Heterotrophic growth rate
6
: Heterotrophic decay rate
0.62
BH
: Monod constant for substrate
20
KSH
: Monod constant for oxygen
0.20
KOH
: Monod constant for ammonium 0.01
KVNH
N
: Monod constant for alkalinity
0.10
K,NOH : Monod constant for nitrate
0.50
: Fraction of denitrifiers
0.80
Unit
g COD/g COD
g COD/g COD
g N/g COD
g N/g COD
g COD/g COD
Unit
d"1
d"1
g COD/m3
g COD/m3
gN/m 3
g HCOVm3
gN/m 3
-82-
Kinetic constants of autotrophs in activated sludge model
Constant
default value
HA
: Autotrophic growth rate
0.8
BA
: Autotrophic decay rate
0.15
K^
: Monod constant for nitrate
1.0
KQA
: Monod constant for oxygen
0.40
KAA
: Monod constant for alkalinity
0.30
Kinetic constants of hydrolysis in activated sludge model
Constant
default value
KHX
: Particulate substrate hydrolysis 0.005
KHS
: Soluble substrate hydrolysis
4.00
K HND : Ammonification
1.00
r\ h
: Correction for lower anoxic
hydrolysis
0.40
Kinetic constants for simultaneous precipitation
Constant
default value
KFe
: Iron oxidation rate
50
KMe
: Precipitation rate
1.0
Kp 0
: Resolubilisation rate
0.40
Secondary clarifier
Constant
default value
GT
: Total flux
Gg
: Gravity flux
GF
: Flow
flux
Vg
: Setüing Velocity
XJS
: Sludge concentration
VF
: Flow velocity
A
: Area of clarifier
h
: Height of clarifier
QE
: Effluent
flow
QR
: Return sludge
flow
Qp
: Waste sludge
flow
V0
: Max settling velocity
137
k
: Sludge characteristic constant
037
X NS
: Non settled suspended solids
XS Ini , : Floating particles in sludge
10
XS N 0 3 : Max non settled SS due to N 0 3
KN03
: Monod constant for SS
20
S
:
NO3
Nitrate concentration
Unit
d"1
d'1
g N/m 3
g COD/m 3
g HCOVm 3
Unit
m 3 /(g COD d)
m 3 /(g COD d)
Unit
/ ( g Fe 2+ d)
m 3 /(g Fe 3+ d)
d'1
m3
Unit
g/m 2 /d
g/m 2 /d
g/m 2 /d
g/m 2 /d
g SS/m 3
m/d
m2
m
m 3 /d
m 3 /d
m 3 /d
m/d
m 3 /kg
g SS/m
g SS/m 3
g SS/m 3
g N0 3 /m 3
gN0 3 /m 3
-837.DISCUSSI0N OF RESULTS
In this chapter the results presented in chapter 5 and 6 will be discussed. The
discussion will focus on two aspects:
- the general treatability of the wastewater of Bilbao in a biological activated
sludge process
- comparison between the two process lines investigated (CONV and FMCT)
7.1.
Primary settling
The results from the two process lines are similar. All data from the intensive periods
4,5,6 and 7 are given in Figure 7.1 and 7.2. Figure 7.1 shows the suspended solids in
the effluent as a function of suspended solids in the influent. For the typical influent
concentrations, the removal efficiency is approximately 50 per cent, which is in the
low end of the normal expected range of 40-70 percent (Abwassertechnologie, 1988).
Figure 7.2 shows the COD reduction over the primary clarifier which amounts to 2535 per cent. The removal of inorganic suspended solids is slightly higher than that of
VSS which means that the ratio CODT^/SS increases slightly over the primary settler
as seen in table 7.1. The ratio CODT^/VSS is essentially unchanged over the primary
settler, indicating that the average composition of the suspended organic matter is
not significantly affected by the primary settling. The slight increase is soluble COD
is caused by hydrolysis of suspended solids during settling. In this case approximately
3 per cent of the particulate COD has been solubilized during primary settling.
Fiq.7.1.
Periods
,
,
SSe v s SSi i n P r i m a r y s e t t l e r
4 , 5 , 6 , 7 . L i n e s CONV a n d FMCT.
. , . ,
. . . .
■ ,
. . . .
, , , ,
. . . . I . . . ,
i
i
i
i
1
1
1
1
250
D
D
200
a
en
E
\_^
+>
C
dl
D
6
DD
150 ° D
D
D
• D fr
C
° /'S
D
D
D
100
D
a
D
B
D
D
n
CP
D
D
nD
9D
.p
•
■ ■ ° Ba
D
j
?
D
D
00
p
° n
mi
D
D
DD
;
a
?
d?
D D
D
■
_ -'
Do
D
Eb
D
D
b
D
.
D
D
:
^ b
D •
P,
a
D
D
m
.
D.%..:.... °
D
UUISl
D
D
□
m
D
D
D
'
a.
D
°
DD
D
50 l i l i
50
|
1 l
100
1 1
l i l i
150
1 1 1 1
200
i i i i 1 i i i i
250
SSinfluent
300
l
350
(mg/l).
l
l
l
I l l 1
400
450
500
F i q . 7 . 2 . CO De vs CO Di in Primary settler
Periods 4,5,6,7. Lines CO NV and FMCT.
I ! I I I I
600
500
tflU
O)
5
400
+>
c
m
□
D
U-
D
d- Q
300
ai
Q
o
00
ai
D
D
DD
q *
%a
fia
¡O
□
PB?
200
100 I
1 I
100
I
I I
I
200
I
I
1 I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I
300
400
500
600
700
CODinfluent (mg/l).
800
900
1000
86
Table 7.1 Primary Settling. Period 4,5,6 and 7, average values.
Parameter
SS
VSS
NVSS
COD
T
Influent
Effl. primary
% reduction
COD
s
CODT.s
CODTJ
SS
CODT.s/
VSS
265
177
88
. 475
128
347
1.31
1.96
134
97
37
336
138
198
1.48
2.04
49
45
58
29
-8
43
-
-
Results from full scale operation of primary clarifiers, show that the removal
efficiency is somewhat higher than in the pilot plant.
7.2.
Activated sludge process
Various aspects of the process will be discussed, including nitrification, sludge
quality, effluent quality, sludge yield and energy consumption
7.2.1 Nitrification
The pilot plant has been operated to get nitrification at high operating temperatures. This has been achieved as shown at Figure 7.3 and 7.4. To obtain nitrification at 23°C a F/M-ratio of 0.25 kg BOD5/(kg VSS • d) or an aerobic sludge age
of 11 days was needed. These values are a result of low pH and low alkalinity
during the experiments in period 4 and 5. Model calculations - see chapter 6 have shown this. The values corrected for the low pH can be found in Table 7.2,
together with the design values at 17CC.
The low pH in the secondary effluent in the experiments, is due to the low
alkalinity (approx. 2,5 mmole/HC03") in combination with the high nitrogen
Fig.7.3.NNH3 and NN03 final effluents
vs F/M. T M 9 and 23 a C.
Average values periods 3,4,5.
en
OU
NH4N anc N03N In effluent (mg/l)
+
19«
40
30
X ""
. . . . _._1 9 * . _ : - - - .
20
00
""""■5
f
""-..
X
10
19"
n
19'
U "1
0.1
0.2a
¥~'~~
0.3
.a.
0.4
0.5
0.6
0.7
F/M (kg BOD/kg VSS.day)
+
CONV.NN
H 3
*
CONV.NN03
D
FMCT.NN
H 3
x
FMCT.NN03
Dashed lines indicate tendency at 232C
0.8
0.9
Fiq.7.4.N-NH3 in effluent vs Aerobic
sludge aqe.CONV and FMCT systems.
Data for periods 3 — 4 — 5 — 6 _ 7.
(mg/1)
50
Äft
+
-i"
40-1
•*-"fério(ls--6"7"'
30
2010-
Periods 3—4—5
ut
B.ft
oo
oo
#*
4 - 22.7%
+
+
22,8-°t
T
Labeled the teiiperatures for every
period.
+
lift
-4=-
20
Aerobic sludge age (days)
23.ft
"î"
aft
40
-89content of the raw wastewater (approx.40-50 mg N/1). The alkalinity consumption
of the nitrifiers (0.14 m mole H + / mg N oxidized is so high that if more than 10
mg NH4-N/1 is to be nitrified the alkalinity of the water needs to be increased
either by addition of base or through denitrification. Addition of base will not
solve problems with denitrification in settlers during summer, and the suspended
solids escape resulting from denitrification.
The results obtained with nitrification as given in Table 7.2 illustrate that the rate
of nitrification is within the normal range as long as pH is 7-7.5. In this range
nitrification proceeds with approximately twice the speed obtained at pH 6.2-6.8.
The normal range for the maximum growth rate of nitrifiers is around 0.8 d"1 at
20°C /Henze et al. 1987/
Table 7.2 Nitrification. Estimates for increased pH based on experimental results.
Maximum
F/M-ratio
kg BODj/kg VSS • d
Minimum
ox, aerobic
d
Experiments
0.25
Model, pH(7-7.5)
A, max
Temp.
d"1
°C
11
0.4
23
0.40
6
0.8
23
Model, pH(7-7.5)
0.30
9
0.6
20
Model, pH(7-7.5)
0.25
11
0.4
17
Figure 7.2 and 7.3 shows that there is no difference in nitrification in the two lines
investigated.
Table 7.3 shows measured and model calculated alkalinity changes during
nitrification in experimental period 4 and 5. It can be seen that the model predicts
the alkalinity change reasonably.
-90
Table 7.3. Alkalinity changes in biological process, period 4 and 5, mmol HC03"/1
Period 4
Period 5
CONV
FMCT
CONV
FMCT
Influent
(measured)
4.52
4.32
6.12
5.22
Effluent
(measured)
0.52
0.64
2.26
2.14
Effluent
(calculated)
0.00
0.00
0.00
0.00
7.2.2 Activated sludge quality
The specific oxygen uptake rate is similar in both lines in spite of the fact that the
FMCT-line was operated at higher MLSS concentrations (3-6 g/1) while the
CONV-line at lower concentration (0.6-3 g/1) - see Table 5.1. This is shown in
Figure 7.5. The observed values were approx. 10-20 mg 0 2 /(g VSS.h) in periods
4,5,6 and 7 which are within the expected range (Kristensen et al., 1992). The
activated sludge in the experiments have had a VSS/SS-ratio of 0.6-0.8, which is
in the expected range as well.
Sludge volume indexes as well as abundance of filamentous microorganisms varied
significantly during the experimental periods. The lowest SVI's were observed in
periods 4 and 5 characterized by high sludge age (and consequently low F/M
ratio). Both lines revealed at those periods average SVI's between 41 and 65
ml/g. The highest SVI's were observed in the CONV-line in periods 2,3 and 7, up
to 426 ml/g.
The relation between SVI and aerobic sludge age is shown in Figure 7.5 a. In
general, in the CONV-line the relation between SVI and aerobic sludge age is
hyperbolic. At aerobic sludge ages above approx. 10 days SVI's do not exceed 100
ml/g. In the FMCT-line the relation between SVI and sludge age is loose and
5 .. So ip e c iifif i c
ïq.7
/ .. b
M L V S S . CONV a n d
e rax.Q
r a t e \v :
o x y _ g e n u p tt a
a kk e
FMCf. P e r i o d s
4,5,6,7
50
40
L
0
_c
ui
30
D D
LO
en
o
en
E
\-/
D DD
20
DD
D
'P. u ,
a Q
D
D
□
CD
G
I
3D
en
□
rP
D
Sn D £
. . t l . p . BP . .
10
o fl D°nb
0
2000
D
_
§
n
4000
6000
r
8000
MLVSS ( m g / l ) .
N o t e : Values above 3.500 mg/1 of MLVSS belongs to t h e FMCT line, while values below
2.500 mg/1 belongs t o the CONV line.
-92-
Fig.7.5a Relation between SVI
and Aerobic Sludge Age
500
Sludge Volume Index (ml/g)
400
300
200
100
10
20
30
Aerobic sludge age (d)
-93rather insignificant. The SVI's vary between 41 and 167 ml/g. This is explained by
the large quantities of sludge accumulated in the FMCT-line big clarifier. Anaerobic conditions in the clarifier sludge layer presumably controlled occurrence of
both, Sphaerotilus natans and type 1701 which were the microorganisms most
drastically influencing SVFs as shown in Figure 7.5 b.
In all experimental periods biological foaming occurred but at different intensities.
Microscopic observations indicate the responsible microorganism - Nocardia sp.
As shown in Figure 7.5 c, Nocardia was present at all experimented sludge ages.
Haliscomenobacter hydrossis occurred in significant abundances at aerobic sludge
ages below about 20 days. Neither Nocardia sp. nor H. hydrossis influenced
significantly SVFs. Fungi appeared in the FMCT-line in period 1 as dominating
filaments without significant increase of SVI. During this period marked decrease
of pH was observed in FMCT-line. While pH in CONV-line was 7.4, in the
FMCT-line it was 6.8. Type 0041 occurred at small abundance in both lines during
several experimental periods without causing problems.
In general, the microscopic observations and SVI's were within the expected
occurrence described in the literature for completely stirred activated sludge
reactors. The single exception was Nocardia sp. which occurred at all situations at
significant abundances. That is not the usual case. Nocardia foam floated on
aeration tanks and covered their surface, in some periods almost completely. In
most periods no significant difference was observed between the two lines.
Average relative abundance through all periods was in CONV-line 3 and in the
FMCT line 2. This was influenced mainly by the two last periods, No 6 and 7.
These were characterized by low temperature, 8 °C, and no nitrification. The
main difference between the two reactors was the aerobic sludge age fraction.
While in the CONV-line the fraction was as high as 0.67-0.97, in the FMCT-line it
was only 0.31-0.83. Thus the recycled sludge dwelled for significant periods of
time in anaerobic conditions since no nitrification occurred at that time. On
contrary, during periods 4 and 5 the temperature was high, around 23 °C, and
nitrification occurred. The aerobic sludge age fraction in the FMCT-system was
94
Fig.7.5b Relation between Abundance of
Filaments and SVI
(Sphaerotilus n. and Type 1701 only)
500
Sludge Volume Index (ml/g)
400
300
200
100
1
2
3
4
5
6
Cummulative Relative Abundance
95
Fig.7.5c Occurence of Filamentous Microorganisms at Various Aerobic Sludge Ages
Nocardia
H. hydrossis
S. natans
T. 1701
10
20
30
Aerobic Sludge Age (d)
40
-96higher than in the low temperature periods, 0.7 compared to 0.3. The conditions
in the clarifier blanket were partially anoxic due to the nitrates present at high
concentrations. From these observations it could be concluded that keeping the
recycled sludge anaerobic for a period of time may contribute to suppressing
Nocardia sp.
This finding is supported by Mori et al., who found that an anaerobic-oxic process
controlled Nocardia sp. to acceptable levels. Process configuration, however, was
in their experiments quite different.
The S\Ts of the activated sludges influence the recycle solids concentrations as
shown on Figure 7.6. At high SVl's sludge failed to thicken sufficiently and low
concentrations of solids was recycled into the aeration tank. This resulted in low
mixed liquor concentrations (see Table 5.1 period 7, CONV line). For SVTs of
100 -150 ml/g, 8-12 g SS/1 can be expected in the return sludge in the CONV
line. The FMCT lines gives higher recycle solids (12-16 g SS/1) due to the higher
retention time. The solid line in Figure 7.6 illustrates that in the FMCT line
considerably higher recycle solids concentrations are obtained than those found in
the SVI test.
7.2.3 Settling velocity
The relationship between initial zone settling velocity and SVI has been investigated. The observed initial zone settling velocities vary from 0.1 - 4,3 m/h - see
Table 5.13. Using the approach by Daigger and Roper 1985, and the expression
V. = V 0 - e k ' X i
the data has been grouped in 4 ranges according to the SVI. Based on these 4
groups, the k-value for each group has been estimated and the result is shown in
Figure 7.7.
Fig.7.6.Recycle SS vs SVI.Recirculatiori
rates 30-78%.Solid line illustrates s o lids concentration in SVI test
Recycle SS (g/l).
CO
-J
"i
i
1
1
50
100
150
200
r
250
SVI (ml/g).
300
350
400
450
Fig.7.7. Settling velocity vs
MLSS for different SVI ranges.
Ln VI (m/h)
CD
oo
6
MLSS (g/l)
Range 1 - S V I 1 8 - 6 3
-B- Range 2-SVI 64-106
Range 3-SVI 110-208
- * - Range 4-SVI 3 5 3 - 8 3 5
Represented regression lines for
every range.
F i g . 7 . 8 . K vs SVI average in every
range.
2.5
.:+"
M
1.5
k tea
CO
(O
1
0.5 4
.+.
4
o
:
Too
K is the slope of regression lines
plotting In Vi vs HL5S.
~m
300
SVI (il/g)
400
500
600
- 100-
The figure illustrates, that for increasing SVI the initial settling velocity for a
given MLSS decreases. In Figure 7.8 the settling constant, k, has been plotted
against SVI. There is a good correlation between the two parameters. The k
values obtained in this study are shown in Table 7.4 together with the k values
found by Daigger & Roper, 1985. They measured stirred SVFs which gives lower
values than unstirred SVTs. Thus the sludge in the present experiments has a
somewhat lower settling velocity.
Table 7.4. Comparison of k-values obtained for settling characteristics.
SVI range
(Daigger & Roper)
36-64
65-108
111-251
285-402
k
0.25
0.32
0.52
0.85
SVI range
(experiments)
29-63
64-106
110-208
353-835
k (experiments)
0.14
0.42
0.66
2.33
k (modelling)
7.2.4 Effluent quality
The effluent quality will be discussed in two parts - the soluble and the suspended. The soluble concentrations will be a result of the influent and on the
biological processes in the treatment plant.
Soluble COD in the effluent can be divided in many fractions. Of primary interest
is the two fractions biodegradable and inert (non-biodegradable). The inert COD
concentration in the effluent can be estimated as:
CODincrt, „,„„,. = COD^,,,, - 1,5 • BODS«,,,,,.
Fiq.7.9.C0D inert (s)e vs C0D(s)i.
CONV and FMCT.— — — —
Average values periods 1 3 4~5 6 7.
COD inert (s) eff luent (mq/1).
150
200
COO (s) influent (mq/1).
COD inert soluble = COD soluble - 1.5 B0D5 soluble
-102In Figure 7.9 the correlation between effluent inert soluble COD and total soluble
COD in the influent is shown. It is seen that approximately 15 per cent of the soluble COD in the influent ends up as soluble inert COD in the effluent. The soluble inert COD in the effluent does not necessarily has its sole origin in the
soluble COD of the influent.
Possibly a part of it is a result of biomass decay (Artan et al., 1990), but as a
simplified approach the correlation given, in Figure 7.9 can be used.
Figure 7.10 shows that temperature and F/M-loading influences the total soluble
COD in the effluent. Increasing F/M-loading will increase soluble COD in the
effluent. Decreasing temperature has a similar effect. The observed increase in soluble COD can not be explained by the increase in soluble BOD in the effluent.
Figure 7.11 shows that BOD does only increase marginally. Thus there is an increase in inert soluble COD for both low temperature and high load. This fits well
with the observations by Sollfrank and al., 1992 that at low temperatures more
soluble inert is found in the effluent.
High load can in this respect be regarded equal to low temperature in the sense
that under both conditions the degradation of organic matter is less complete.
Figure 7.11 illustrates that removal of soluble BOD is very efficient under all the
investigated conditions. Total BOD in the effluent is shown in Figure 7.12 . For
all investigated F/M-loadings 0.15-0.60 kg BOD/(kg VSS • day) the total BOD is
below 20 mg/I and the total COD below 50 mg/1. Thus the quality of the effluent
with respect to organic matter can live up to the expected effluent criteria of 25
mg BOD/1 and 125 mg COD/1 according to the EEC directive (91/271/EEC) of
21 May 1991.
Fig.7.10.CODs in effluent vs F/M and T5.
Average values periods 4~5_6_7
60
CODs in effluent (mg/l)
50-
o
w
40
FMCT High T9
30-
**""C0NV-Iöw-T*- B - FMCT low Ts
-*-
?.0
0.1
0.2
Labeled the temperatures.
0.3
0.4
0.5
F/M (kg BOD/kg VSS.day)
CONVhighT-0
0.6
0.7
Fig.7.11.BODs in effluent vs F/M and T9.
Average values periods 4~5_6_7
BODs in effluent (mg/l)
o
0.1
0.2
Labeled the temperatures
0.3
0.4
0.5
F/M (kg BOD/kg VSS.day)
Fig.7.12.BODe vs F/M.
Average values periods 4 5 6 7
on
BODe (mg/l)
¿\J
J
I
X
i
15
4
FMCT
X
CONV
I
X
+
10
■
■
"
*
4
o
UI
■
X
4
X
5
.. _
o0.1
0.2
0.3
F/M (kg BOD/kg VSS.day)
0.4
0.5
0.6
106
In periods with bulking in the pilot plant, the effluent quality with respect to
suspended solids was excellent due to filtering of the effluent through the sludge
blanket This effect is difficult to obtain in full scale plants because of problems
with controlling the sludge blanket under storm water conditions.
7.2.5 Yield coefficient, activated sludge
The sludge production is strongly influenced by temperature and F/M-load. In
Figure 7.13 a and b it is shown that high load and low temperature increases
sludge production considerably. In Table 7.3 values relevant for design are given.
It is seen that for constant F/M of 0,2 kg BOD/(kg VSS-d) the sludge production
in winter (8°C) is twice as high as in summer (23°C). If the load is increased
during winter because of no need for nitrification, then the yield is 2,5 times that
during summer. There is no significant difference between the yield for the 2 lines
investigated as long as they are operated at similar F/M-ratios.
Table 7.5 Observed yield coefficients for the CONV and FMCT line.
F/M
Temp
kg BOD/
(kg VSS-d)
°C
kg VSS/kg
BOD
kg SS/kg
BOD
kg COD/kg
COD
0.20
23
0.23
0.32
0.20
0.20
17
-0.3
0.45
-0.27
0.20
8
0.41
0.65
0.36
0.40
8
0.54
0.78
0.48
Observed yield
There is a close relationship between the F/M-ratio and the aerobic sludge age as
expected. This is shown on Figure 7.13 c. No difference is seen between CONV
and FMCT line. This means that the regression line given in Figure 7.13 c can be
used to convert between F/M-ratio and aerobic sludge age as wanted.
Fi q.7.13a.Y observed vs F/M and T~.
CONV and-FMCT.
— - _ —
Yob:
Average values periods 3 4 5 6 7.
(kg VSS/kg BODreioved)
o-J
0.4
0.6
F/H (kg BOO/ kg VSS.day)
Fi q- 7.13b- Y observed vs F/M and T - .
CGNV and FMCT.
Average values periods 3 — 4 - 5 _ 6 _ 7.
i obs (kg TSS/kg BODrenoved)
o
00
A
0.6
F/M (kg B0Ü/ kg VSS.day)
FIG. 7.13 c
Reciprocal Aerobic Sludge Age v:
Average values all periods
-i—i
0.4
F/M.
i_
FMCT 1
-
CONV D
>,
-S
0.3
Ql
en
<
0.2
o
Ql
CO
t)
CD
D
m
JD
0
L
ai
<
0.1
0 -
-0.1
-i
i—■—■—■—r
0.2
0.4
0.6
F/M ( k g BOD/kg VSS.day)
0.8
-1107.2.6 Energy consumption
Energy consumption and yield is closely related. Figure 7.14 shows the specific air
consumption in the two lines. The air consumption is a function of 3 factors:
- yield;
- D.OinMLVSS;
- aeration efficiency.
It is seen that the air consumption is high when the yield is low. The energy
consumption for the same F/M ratio was approximately equal in both systems.
Since the CONV-line was operated in general at lower concentrations of dissolved
oxygen in the mixed liquor, the oxygen transfer was for this line higher by 10-15
%. This can not be easily seen from the data because of other factors influencing
the oxygen transfer rate as well, for instance significantly higher mixed liquor
solids concentration in the FMCT-line than in the CONV-line. The higher solids
concentration tends to increase oxygen transfer efficiency in the FMCT-line due
to a higher volumetric reaction rate. At the same time increased air flow in that
line has the opposite effect. The oxygen transfer efficiency in the pilot plant is in
general rather low (2-4 per cent), because of low water column depth in the
aeration tanks.
7.3 Secondary settling
The strongest influence on secondary settler performance in this study has been
the influence of nitrate. Nitrate causes denitrification in the settler, and nitrogen
bubbles may be produced which will tend to float the suspended solids. This
phenomena is called rising sludge. Figure 7.15 illustrates this effect. At low nitrate
concentrations (0-3 mg NCyN/l) the suspended solids concentration in the
effluent is stable and low, 5-20 mg SS/1. At nitrate concentrations above 6-8 mg
NO3-N/I suspended solids in the effluent gets unstable, and at higher levels, 15-50
F¡g.7.14. AIR CONSUMPTION VS YIELD.
AVERAGE VALUES PERIODS 4,5,6,7.
OKO
m3 air/Kg BOD5 removed
¿OU
200
150
100
•
■
+
\
■
---
4-
4_
50
o0.1
0.2
0.3
0.4
0.5
YIELD(Kg VSS/Kg BOD5 removed)
CONV
+
FMCT
0.6
0.7
Fig.7. 15 ..TSS vs N-N03 in final effluent
All values for periods 4 - 5 - 6 _ 7 .
J
i
i_
100 -
75
o
O O:
en
E
50
ai
en
co
O
< * ■ ■ ■
O
25
o
o
o
o
s>
•<£>•
o
oo
o o
D^va
:<$>
í
.o
So o
«> C0NV
O FMCT
0 ~i
10
20
1
r~
-I
30
N-N03e (mg/1)
1
I
1
40
1
1
1
I
50
-113-
mg SS/l. This illustrates that nitrogen bubble generation is not always found when
nitrate is high. Many factors influence the generation of nitrogen bubbles, among
others:
- nitrate concentration;
- denitrification rate (incl. temperature effects);
- solids retention time in the settler;
- nitrogen gas concentration in MLVSS;
- oxygen concentration in MLVSS.
The complicated interplay between these factors can not be solved through the
results of these investigations. But the results illustrate that nitrate in the effluent
might deteriorate the effluent quality with respect to SS, BOD5 and COD. Temperature and hydraulic retention time in the settler also effects SS in the effluent.
The temperature effect seen in figure 7.16 is mainly the effect of nitrate which is
found in the effluent at high temperatures. Increasing hydraulic retention time has
a minor impact and reduces SS. A similar minor impact is seen for the settler
overflow rate as shown in figure 7.17. In most cases this load has been low 0.1-0.7
m/h and for these loads only a slight effect would be expected.
The sludge blanket height does not seem to have had any effect on SS in the
effluent - see figure 7.18 and 7.19, as long as it is more than 1 m below the water
surface.
For all experiments there was no significant variation in performance of the
settlers in the FMCT and the CONV line. This is remarkable when considering
the difference in the design of the two settlers. It indicates that the operational
parameters compared - blanket height and overflow rate - seems to be general for
both types of settlers.
SSe (mg/1)
Fig.7.16.SS in effluent vs hydraulic
retention time in the secondary settler.
Average values for periods 4 — 5 — 6 — 7.
Hydraulic retention tine (h)
50
SSe (ig/l)
Fig.7.17.SS in effluent vs overflow rate
in secondary settler.
Average values for periods 4"5~6"7.
40302010-
.2
0.4
.8
1
1.2
Overflow rate (n/h)
1.4
1.
1.8
Fig.7.18.SS in effluent vs Blanket level
in secondary settler for CO NV system.
j
i—I—i
i i i I i i i i 1 i i i i i i i i ■ i i i i
i — L
i
i ■ ■ ■ i
120 110 4
100 -i
90 -\
80
70 -.
en
E
60 4
50
40
. D
30 -3
20
D D„ .
£>
10
*a*a
a•
0 -Ì
-T - T
1 1 1
1 1
0.5
1 T"
' I''''I '
1.5
2
2.5
H.BLANKET Cm)
Note: Data for periods 267 (no nitrification)
3.5
f IG.7. 19.SS in effluent vs Blanket leve
in secondary settler for FMCT system.
en
E
ai
in
tsi
120 110 \
100 \
90 -Ë
80 \
70 \
60 \
50 \
40 -j
30 \
20 \
10 \
0 -=
•••••••
' Q • ■•
Q
' ' '!' 'D' ' ■ ' " ' '
;
a ' '■ '
a
a ;
B'
V'
' 'jï' 'D' ' ' ' 'f '
•••••□
' b'n.* ' D ' n ' a ^ ' :
D ' ' '.
a
•
-i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—r
0.5
1.5
2
2.5
H.BLANKET Cm)
Note: Data for periods 267 (no nitrification)
3.5
D'
-
- 118
7.4.
HEAVY METALS
The pilot plant influent, the primary effluent, the secondary effluent and the
sludges were analyzed for heavy metals (Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn).
Starting from period 4 (July 90) the pilot plant influent was taken from the
influent to the full-scale primary treatment plant in Galindo. Since not yet all the
sewers connecting the wastewater from Bilbao to the treatment plant have been
constructed, the incoming wastewater does not represent the ultimate
composition.
Comparison of heavy metals content found in pilot-plant sludges and regulated by
EC Directive (86/278/CEE from 12.6.1986) is in Tab. 7.6. Metals are compared
to the maximum permissible concentrations in soils at low pH what is the most
strict standard for comparison. So far, the concentration of metals in the biologically treated wastewater and in the sludges are low in comparison to applicable standards. As can be seen from the table, all concentrations (except asingle
value of Ni in primary sludge) are within acceptable limits.
Tab.7.6. Concentration of metals found in pilot plant sludges
mg/kg of dry solids
Metal
Cadmium
EC regulation for
soils pH<7
Primary sludge
Secondary
sludge
20
2-5.9
3.9 -5.9
Copper
1000
152-492
75.5-347
Nickel
300
90.7-1057
66-249
Lead
750
91.5-218
126-236
Zinc
2500
471-1018
460-983
16
0.12-1.32
0.49-3.1
1000
27.6-136
25.8-46.6
Mercury
Chromium
-1197.5.
GENERAL WASTEWATER CHARACTERISTICS
The wastewater used in the experiments has characteristics similar to normal
municipal wastewater. This holds for the concentration of the various components and
the ratios between these. Toxic substances (e.g. metals) have not been observed to
influence the treatment results. However it must be pointed out that the wastewater
used is not identical to what will be treated in future in the full scale plant.
- 120 8.
CONCLUSIONS
8.1.
General conclusions
The primary settling is normal as expected with a SS removal of about 50% and
a COD removal of 25-35 per cent. The removal of inorganic suspended solids is
slightly higher than that of VSS.
The effluent quality with respect to BOD and COD is well below the proposed
EEC standards for both systems. The soluble inert COD in the effluent is approx.
30-40 mg/1.
Increasing F/M-ratio increases soluble COD in effluent. Decreasing temperature
has a similar effect.
To obtain nitrification at 23°C a F/M-ratio of 0.25 (kg BOD^/kg VSS.d) or an
aerobic sludge age of 11 days was needed. These values are a result of low pH
and low alkalinity during experiments. Calculated nitrification rates with an
activated sludge model for pH-(7-7.5) are normal so no additional inhibiroty
effects on nitrification was detected.
The strongest influence on secondary settler performance in this study has been
the influence of nitrate. Nitrate in effluent give problems in settler producing high
SS in the effluent.
Problems with low alkalinity and denitrification in settlers can be solved by
providing a process with nitrification and denitrification. COD/N-ratio in the raw
wastewater is sufficient for denitrification. In primary settled or precipitated
wastewater the ratio is rather low, which indicates that external carbon might be
added to satisfy part of the carbon demand for denitrification.
The secondary settling performances in the two systems are similar. FMCT gives
higher SS recycle concentration and provides higher stability in operation.
-121 The observed yield was similar for both systems for similar F/M ratios. The yield
is highly influenced by temperatures and F/M-ratio. For similar F/M-ratio the
yield at 8* C was approx. twice the yield at 23° C.
The sludge settling velocity was in the normal expected range.
The removal of phosphorus was within the expected range for removal of P
through biological sludge production, approx. 2 mg P/l.
The removal of N was approx. 8 mg N/1 due to surplus sludge production. In
periods with nitrification a similar amount was denitrified. The overall removal
was 10-30% which for the high range indicates some denitrification in periods
with nitrification.
Energy for aeration was practically equal for the two systems for similar F/Mratios. The energy consumption was lower at higher observed yields.
Activated sludgefilamentousbulking occurred in some periods. It has been shown
that increasing aerobic sludge age above approx. 10 days eliminated bulking
problems in the CONV system. On the other hand, the FMCT system never
suffered from extreme bulking.
Biological foaming caused by Nocardia sp. was rather intensive and a general
phenomena for the particular wastewater and systems configurations. It can be
concluded from the experiments that exposure of the sludge to anaerobic
conditions can significantly suppress occurrence of Nocardia sp.
The wastewater used in the experiments has characteristics similar to normal
municipal wastewater. This holds for the concentration of the various components
and the ratios between these. Toxic substances (e.g. metals) have not been
observed to influence the treatment results.
-1228.2.
New system versus traditional system
Over the expected benefits of the FMCT system the following conclusions can be drawn:
Allows for better adjustment of biomass to instantaneous needs due to storage of
large amounts of biomass in the big clarifier.
Aeration tank volume could be reduced by using high MLVSS concentrations
(normal range 3000-6000 mg VSS/1). Reduction of volume could be approx. 50%.
The clarifier volume of the FMCT system was approx. 3-3.5 times the volume
needed for the CONV secondary clarifier.
There is no reduction in energy consumption in aeration tanks for similar F/Mratio.
The effluent quality was not improved compared to CONV system.
Excess sludge volume was lower due to higher concentrations. Dry matter
production (yield) is similar in the two systems.
Sludge in FMCT was more stabilized with a lower percentage of VSS.
Less bulking and foaming problems occurred in FMCT system.
-1238.3.
Modelling
Model has shown to be a valuable tool for interpretation of experimental results
identifying irregularities in experimental data.
The results from model follow the experimental results, and the modelling has not
revealed any irregularities in the wastewater composition of Bilbao, nor in the
process performance of the pilot unit.
The model can describe the actual settler performance and the performance of
the biological reactors.
- 124LIST OF SYMBOLS
AS
=
Activated sludge
BODe
=
BOD effluent (mg/1)
BODr
=
BOD removed (Kg/day)
BODs
=
BOD soluble (mg/1)
CODe
=
Chemical Oxygen demand effluent (mg/1)
CODi
=
Chemical Oxygen demand influent (mg/1)
CODinert (s)
=
COD inert soluble (mg/1)
CODs
=
COD soluble (mg/1)
COD (s)i
=
COD soluble influent (mg/1)
CODT^
=
Particulate COD (mg/1)
DO
=
Dissolved Oxygen in aeration tank (mg/1)
Fexcess
=
Sludge wasted and lost (Kg VSS/day)
F/M
=
Food mass ratio (Kg BOD/Kg MLVSS. day)
H. Blanket
=
Blanket level in secondary settler (m)
K
=
Settling constant (volume/mass)
MLSS
=
Mixed liquor .suspended solids (mg/1)
MLVSS
=
Mixed liquor volatile suspended solids (mg/1)
MxO
=
Total sludge mass beginning of period (kg)
Mxl
=
Total sludge mass end of period (kg)
NVSS
=
Non volatile suspended solids (mg/1)
OUR
=
Oxygen uptake rate (mg O^l.h)
P.S.
=
Primary settler
Qi
=
Influent flow (m3/h)
Qr
=
Recycle flow (m3/h)
Qw
=
Sludge wasting flow (m3/h)
R
=
Regression coefficient
SS
=
Suspended solids (mg/1)
S.S.
=
Secondary settler
SSe
=
Suspended solids effluent (mg/1)
125
SSi
Suspended solids influent (mg/l)
SOUR
Specific oxygen uptake rate (mg 0 2 /g VSS.h)
SVI
Sludge volume index (ml/g)
TSS
Total suspended solids (mg/1)
u
Utilization rate (Kg BOD/Kg VSS.day)
Va
Aeration tank volume (m3)
Vi
Initial settling velocity (m/h)
vss
Volatile suspended solids (mg/1)
Vtotal
Total volume: aeration tank + secondary settler
Xa
Biomass concentration in aeration tank (kg MLVSS/m3)
Xi
Initial SS concentration (mass/volume)
Y
Yield coefficient
Yobs
Observed yield coefficient
Maximum specific growth rate autotrophs^"1)
ex
Total sludge age (days)
6a
Aerobic sludge age (days)
o
Beginning of intensive period
i
End of intensive period
All the symbols used for laboratory and plant parameters are included in chapter 3.
- 126 10.
REFERENCES
Abwassertechnologie (1988) Ed. E. Blitz and W. Czysz. Springer Verlag
Berlin 1988 ISBN 3-540-13038-1
Artan, N. D. Orhon and B. Beler Baykal (1990) Implications of
the Task Group Model-1. The effect of initial substrate concentration.
Wat.Res.,24, 1251-1258
Daigger, G.T and R.E Roper (1985) The relationship between SVI
and activated sludge settling characteristics J. WPCF, 5JZ, 859-866
Dupont, R., Henze, M. (1991) Modeling Of The Secondary
Clarifier Combined With The Activated Sludge Model No. 1. Preprint :
IAWPRC conf. on: Interactions of wastewater, biomass and reactor configurations in biological treatment plants. Copenhagen, 21-23 August, 1991.
Eikelboom D.H. and Van Buijsen H.j. (1981). Microscopic Sludge
Investigation Manual. IMG - TNO Report A94a, Delft.
Ekama G.A., Pitman, A.R., Smollen, M. and Marais, G.v.R.
(1984). Secondary settling tanks. Chapter 8 in: Theory, Design and Operation
of Nutrient Removal Activated Sludge Processes, pp. 8.1-8.14. Water
Research Commision, Pretoria, SA.
Gujer, W. (1991) Modeling Population Dynamics in Activated
Sludge Systems. Preprint : IAWPRC conf. on: Interactions of wastewater,
biomass and reactor configurations in biological treatment plants.
Copenhagen, 21-23 August, 1991.
Henze, M., C.P.L. Grady jr., W. Gujer, G.V.R Marais and
T. Matsuo (1987) Activated sludge model no. 1 IAWPRC Sci. Techn. Report
No.l, IAWPRC, London
Kristensen, G.H, P.E. Jørgensen, M. Henze (1992)
characterization of functional groups and substrate in activated sludge and
wastewater by AUR, NUR and OUR. Wat.Sci.Tech.
Mori, T., Itokazu, K., Ishikura, Y., Mishina, F., Sakai, Y. and
M. Koga (1991) Control of Actinomycetes Scum Production by an AnaerobicOxic Process. IAWPRC Specialized Conference on Interactions of
Wastewater, Biomass and Reactor Configuration in Biological Treatment
Plants, Copenhagen, 21-23 August.
127
Process Control manual for Aerobic biological waste-water
treatment facilities (1977). EPA - 430 / 9-77-006.
Sollfrank, U., J. Kappeler and W. Gujer (1992) Temperature
effects on wastewater characterization and the release of soluble inert organic
material. Wat. Sei. Tech.
Standard Methods for the Examination of Water and Wastewater
(1989). 17,h edition APHA, AWWA, WPCF.
Vesilind P.A. (1979). Treatment and disposal of wastewater
sludges. Ann Arbor Science, Ann Arbor, Mich.
-129
ANNEX 1
DRAWING AND PHOTOGRAPHS OF
THE PILOT PLANT AND LABORATORY
SECONDARY SETTLER
FINAL EFFLUENT TANKS
BLOWERS
INDUSTRIAL WASTES RECEPTION TANK
00
AERATION TANK
DISSOLVED OXYGEN, pH AND T?, METERS WITH
AUTOMATIC CLEANING
134
LABORATORY
\^-/W^f^í^i&}-
INDUSTRIAL WASTE DOSAGE TANK
.-v -^---^:-':^^-'
CONTROL PANEL
136
LABORATORY
137
LABORATORY
139
ANNEX 2
ANALITICA!. METHODS
-140ANNEX 2
DESCRIPTION OF THE ANALYTICAL METHODS
Analyses and tests were carried out by laboratory personnel
working shifts for six days a week, so that samples could be
analyzed immediately they were taken. A refrigeration system
was used to preserve the 24-hour composite samples of influent
and effluents from the plant.
The frequency with which analyses were made was the same as in
the transitional and intensive periods; the only change was the
humber of parameters during the various periods.
The analytical methods used as a reference were those of
"Standard Methods for the Examination of Water and Wastewater",
17th Edition, 1989, APHA, AWWA, WPCF.
Here follows a brief description of the analytical methods
which were used.
SST:
Total Suspended Solids dried at 103-1052C.
A known volume of a sample is filtered through a
standard glass fiber filter and the residue contained
in the filter is dried at 103-105SC to constant weight.
The increase in the filter weight represents the
suspended matter.
SSV:
Volatile Suspended Solids calcined at 550 s .
Volatile solids correspond with the weight loss
occurring when the residue resulting from the SST test
is calcined in a muffle furnace at a temperature of
550+50SC.
DBO T:
5
Biochemical Oxygen Demand during a 5-day
incubation period.
A sample is placed in a full, stoppered bottle and
incubated in the dark, at 20 9 C, in the presence of
micro-organisms, excess nutrients and dissolved oxygen
for 5 days. The dissolved oxygen (D.O.) is measured
initially and after incubation. The DBO is calculated
from the difference between the initial and final D.O.
levels.
-141 DBO S:
5
Biochemical Oxygen Demand, during a 5-day
incubation period, of the soluble portion of the
sample.
O.D. :
Dissolved Oxygen.
Dissolved oxygen was measured by means of an oxygen
membrane electrode.
DQO T:
Chemical Oxygen Demand (Total Sample).
A sample is put at reflux for 2 hours in a highly acid
solution together with a known excess quantity of
potassium dichromate (K Cr 0 ) . After digestion,
2 2 7
the potassium dichromate that remains unreduced is
titrated with ammonic ferrous sulphate to establish the
quantity of potassium dichromate consumed and the
oxidizable organic matter is calculated in terms of
oxygen equivalent.
DQO S:
Chemical Oxygen Demand (Soluble)
The soluble DQO is determined exactly the same way as
described above, except that the sample is filtered
through a membrane filter prior to analysis.
N-NH :
3
Ammoniacal Nitrogen
Zn sulphate and sodium hydroxide (pH approx. 10.5) are
added to the sample so as to allow eventual
interferences to precipitate; afterwards it is
filtered. A dissolution is prepared with a known volume
of the filtrate, to which Nessler reactant is added to
develop colour. Ammonia is measured calorimetrically.
NTK:
Total Kjeldah Nitrogen
This determination shows the addition of organic and
ammoniacal nitrogen. The sample is digested at A20 9 C by
means of sulphuric acid, potassium sulphate and a
selenium reactive mixture as a catalyst, so as to
convert the organic nitrogenated compounds into
ammoniacal compounds; afterwards, the ammonia is
distilled in an alkaline medium and absorbed with boric
acid. The NTK is measured carorimetrically by using
Nessler reactant for colour development.
N-NO :
Nitrates
3 The previously membrane-filtered sample, the whiting and
the standard are pipetted in test tubes placed in a
container with cold water. The following is added,
allowing for rest periods between additions, in this
sequence: urea sulphite, sulphuric acid, chromotropic
acid and sulphuric acid. After stoppering the tubes, the
contents is mixed and following a 45-minute rest period
the nitratres are measured calorimetrically.
- 142P-PO :
Orthophosphates
4 Active carbon is added to the sample, which is filtered
through a membrane (0.45 Jim) and then vanadate-molybdate
reactant is added for colour development. The
orthophosphates are finally determined by a calorimetrie
procedure.
P-TOTAL
Total Phosphor
The sample is digested with a nitric-sulphuric acid
mixture until white fumes appear, soda is added to
Phenolphthalein pink colour and neutralized with
sulphuric acid. Total phosphor is measured as orthophosphates, following the above-mentioned procedure.
ALCAL R:
Total Alkalinity
Potentiometrie titration of the sample at ambient
temperature up to pH = 3.7 by using previously
standardized HCl approx. 0.02N. The result is expressed
in mmol/1 CaCO .
3
A & G:
Oils and Greases
Dissolved or emulsified oil and grease are extracted
from a sample acidified by contact with
trichlortrifluorethane and determined gravimetrically.
CI:
Chlorides
Chlorides were determined by the argentimetrlc method.
The potassium Chromate may indicate the final valuation
point of chloride with silver nitrate. Silver chloride
precipitates quantitatively prior to the formation of
silver Chromate.
SULF T:
Total Sulphides
Sulphides are oxidized by excess iodide in an acid
solution. The iodine formed is titrated with a sodium
tiosulphate dissolution, using starch as final point
indicator. For removal of interferences a preliminary
ZnS precipitation treatment is carried out, followed by
filtration.
FENOLES
The acidified sample is distilled with H PO at pH = 4.0
3 4
in order to separate phenols from non-volatile
impurities. In the presence of potassium ferrocyanide,
distilled phenols react with 4-aminoantipyrine to form
an antipyrine coloured compound. This compound is
extracted from the aqueous solution by CHC1 and the
absorbance is measured at 460 nm.
3
- 143DETERG:
Anionic Déte rgents
Anionic detergent s are transferred with methylene blue
from an acquous s olution to an immiscible organic
compound to form a cationic coloured compound. This
process comprises three successive extractions from an
aqueous dissoluti on in an acid medium containing the
sample and an exc ess of methylene blue en chloroform
(CHC1 ) ending wi th an aqueous washing. The intensity
3
of blueing in the organic phase is observed in a
spectrophotometer at 652 nm, as a measure of anionic
detergents.
CN T:
Total Cyanides
The cyanhydric acid is liberated by distillation and
air purging of the acidified sample. The purpose of
distillation is to separate the HNC from eventual
interferences by organic and inorganic contaminants.
The HCN gas is caused to pass through an NaOH washing
solution, in which it is collected. The cyanide
concentration in the soda solution is determined by a
selective electrode.
METALS
Metals were determined by atomic absorption spectrophotometry.
Samples contain particles and organic material
requiring a treatment prior to analysis. Metals can be
found either inorganically or organically bound, in
particles o dissolved. A digestion was made before a
preliminary filtration. A digestion with nitric acid
took place for the following materials: calcium,
magnesium, cadmium, chrome, copper, iron, nickel,
manganese, lead and zinc. For mercury, a digestion was
made with potassium permanganate-sulphuric acid.
In the atomic absorption spectrophotometry, the sample
is aspirated towards a flame in which it is atomized.
A light beam traverses the flame, passes through a
monochromator towards a detector which measures the
amount of light absorbed by the element atomized in
the flame. The amount of energy absorbed at a
characteristic wavelength in the flame is proportional
to the concentration of the element to be analyzed in
the sample.
Determination of calcium, magnesium, cadmium, chrome,
copper, iron, nickel, manganese, lead and zinc was
made by direct aspiration towards an air-acetylene
flame. Mercury was determined by the cold-steam
technique.
- 144 OUR:
OUR
Oxygen Consumption Rate
Agitation of the sample in a partly-full bottle to
increase the D.O. concentration in the sample almost
to saturation. Filling of the 250 ml Winkler bottle
with the sample, insertion of the D.O. meter probe,
placing of the bottle on a magnetic agitator and
recording of the D.O. concentration at 30-second
intervals for 15 minutes or until the D.O.
concentration is limiting (1.0 mg/1).
sp:
Specific Oxygen Consumption Rate
Ratio of OUR in mg D.0./1 x hr to the SSV of the
sludge sample expressed in gr/1 and determined by
gravimetric techniques.
V Sed:
Settled Volume
After homogenizing the sample, pour it carefully into
a 1 litre test beaker and allow it to settle for 30
minutes, at the end of which the volume occupied by
the settled sludge is measured in ml.
SVI:
Sludge Volume Indez
Retio of V.S. after 30 minutes to the SST of the
sludge sample, as determined by gravimetry and
expressed in gr/1.
SED TEST:
Zonal Settling Speed
After homogenizing the sample, pour it carefully into
a 2 litre test beaker (41.5 cm high x 8 cm dia.) and
allow it to settle. Record the heights of the liquidsolid interface at. 5-minute intervals during the first
20 minutes, at 10-minute intervals till minute 60 and
at 30-minute intervals till minute 180. Plot the
height of the interface (in cm) against time (in
minutes) and determine the settling speed as the
maximum gradient ocurring within the first 10 minutes
approximately.
Esp.Grav.:
Specific Gravity
Record the temperature of the sludge sample and weigh
first 100 ml of it and then 100 ml of distilled water
at A 9 C. Specific gravity is the ratio of the weight of
the sample to the weight of water, multiplied by a
corrective factor of the sample temperature.
MICROSCOPIC ANALYSIS
Throughout the project,from 2 to 3 weekly observations
were made of the activated sludge in both lines with a
view to follow up changes ocurring in the sludge
during the various periods. During the "live"
observations, a counting was made both of protozoa and
filamentous micro-organisms. After completion of the
-145
counting, a sample was taken for GRAM and NEISSER
tinting and thus final identification of filamentous
bacteria.
The method used for identification of types of floes
and filamentous micro-organisms was that of D.H.
Eikelboom and H.J.J. Van Buijsen.
lOIHfflqiMliMii^
DÒóólUzóTOÇ11^^
ó"426709
£t?A M eòo
Commission of the European Communities
Diteciotaie ■ Generai fot Science, Research ana Development
Environment Research Programme
ADVANCED DESIGN AND OPERATION
OF
MUNICIPAL WASTE WATER TREATMENT PLANTS
PILOT PLANT FLQW PI,
Vccn/i T 2 m :
PRIMARY
SETTLERS
¡
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TANK
:
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SECONDARY !
SE TTLE RS l
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■ f «Kr
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MAIN DIFFE RE NCE S BE TWE E N BOTH SYSTEMS ABE :
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: £ £ ; «! ; , ' £ ;
AERATION TANKS AND SE CONDARY SE TTLE R WE RE THE RMICALLY INSULATE D
FOR LOW TE MPE RATURE E XPE RIVE NTS
Contract N° EV4V0073E (A)
L. Concha
M. Henze
TECHNOLOGIES FOR E NVIRONME NTAL PROTE CTION
REPORT 1
EUR 15030 EN
JUNE 1992
COMMISSION OF THE EUROPEAN COMMUNITIES
Directorate-General for Science, Research and Development
Environment Research Programme
CONTRACT NO. EV4V-0073-E (A)
L. Concha
M. Henze
ADVANCED DESIGN AND OPERATION
OF MUNICIPAL WASTE WATER
TREATMENT PLANTS
Technologies for Environmental Protection
Report 1
PARL EUROP. Biblioih.
N . C . ^ Áio^o
CI.
EUR 15030 EN
JUNE 1992
Advanced Design and Operation of Municipal Waste Water Treatment Plants
Contract No. EV4V-0073-E(A)
Project coordinator: L. Concha
Ente Vasco de la Energia (EVE)
Edificio Albia 1
San Vincente. 8 - Pianta 14
48001 - Bilbao
Edited by: L. Concha, Ente Vasco de la Energia (EVE), Spain
M. Henze, Technical University Lyngby, Denmark
J. Busing, CEC, DG XII, D-l, Brussels, Belgium
ISBN 2-87263-085-6
Depot legal D 1992/0157/09
This is report No 1 in the Technologies for Environmental Protection Report Series
of the Environmental R&D Programme of the Commission of the European
Communities, Directorate-General for Science, Research and Development.
For more information concerning this series, please contact :
Mr. H. Ott
CEC-DG XII/D-1
Rue de la Loi, 200
B-1040 Brussels
No part of this publication may be reproduced, stored in a retrieval system, or
transmitted in any form or by any means, electronic, mechanical, photocopying,
recording or otherwise, without indicating the above mentioned references.
Publication No EUR 15030 EN of the
Commission of the European Communities,
Dissemination of Scientific and Technical Knowledge Unit,
Directorate-General Information Technologies and Industries,
and Telecommunications,
Luxembourg
© ECSC-EEC-EAEC, Brussels-Luxembourg, 1993.
LEGAL NOTICE
Neither the Commission of the European Communities nor any person acting on
behalf of the Commission is responsible for the use which might be made of the
following information.
E. GUYOT SA, rue Ransfort 25, 1080 Brussels
Printed in Belgium
- III -
FOREWORD
Research work desoribed in the report was aimed at optimizing
design and operation of unified Sludge Age Control Technology
(USCT) in order to enable aotivated sludge plants to treat a
greater variety and strength of municipal and industrial waste
waters than a conventionally designed and operated plant.
The conventional and the new processes were studied in parallel,
eaoh fed with about 85% domestic and 15% industrial waste water
originating from major industrial sources located in the
Galindo/Bilbao area.
The present report is the first issue of a series of Technologies
for Environmental Protection Reports supported under the EC
Environment Programme of DGXII.
J. Busing, DGXII/D-1
1-
CONTENTS
SUMMARY AND CONCLUSIONS
INTRODUCTION
5
7
PILOT PLANT DESCRIPTION
10
2.1. Pumping of domestic sewage
14
22. Primary settling
14
23. Biological reactor
15
2.4. Secondary settling
16
2.5. Sludge recirculation
17
2.6. Incoming industrial waste reception
18
2.7. Means for homogenization, preparation and dosage of industrial wastes.
18
METHODOLOGY
19
3.1. Research schedule
19
32. List of sampling points and general sampling strategy
20
33. List of analyzed parameters
24
3.4. List of continuously measured parameters
27
3.5. Total number of samples and analysis
29
3.6. Scientific and technical team
30
3.7. Analytical methods
31
OPERATING STRATEGY
33
4.1. Control parameter: sludge age.
34
42. Control parameter: F/M ratio
38
-2RESULTS
44
5.1. Operating conditions in intensive periods
46
52. Hydraulic data
47
53. Influent to Pilot plant
48
5.4. Metals in influent to pilot plant
49
5.5. Primary clarifiers effluents
50
5.6. Metals in primary clarifiers effluents
51
5.7. Final effluents
52
5.8. Metals in final effluents
53
5.9. Diurnal variations CONV system
54
5.10. Diurnal variations FMCT system
55
5.11. Activated sludge mass balance (1)
56
5.12. Activated sludge mass balance (2)
57
5.13. Sludge quality
58
5.14. Metals in primary sludge
59
5.15. Metals in activated sludge
60
5.16. Aeration parameters
61
5.17. Energy consumption
62
5.18. Sludge age calculation
63
MODELLING
64
6.1. Introduction
64
62. Concepts of models
64
6.2.1.
Activated sludge model
64
622.
Secondary clarifier model
66
63. CAB description
68
6.4. Model plant
69
6.5. Input data handling
70
-3-
7.
6.6. Operation conditions used for modelling
72
6.7. Modelling and analyzing
73
6.7.1.
Notes on modelling
73
6.12.
Some results from the modelling of the pilot plant
74
6.73.
Calibration of constants in the model
77
6.8. Conclusion
80
6.9. List of symbols
81
DISCUSSION OF RESULTS
7.1. Primary settling
83
7.2. Activated sludge process
86
7.2.1.
Nitrification
86
122.
Activated sludge quality
90
123.
Settling velocity
96
12.4.
Effluent quality
100
12.5.
Yield coefficient
106
7.2.6.
Energy consumption
110
13.
8.
83
Secondary settling
110
7.4. Heavy metals
118
7.5. General wastewater characteristics
119
CONCLUSIONS
120
8.1. General conclusions
120
82. New system
122
S3.
123
Modelling
9.
LIST OF SYMBOLS
124
10.
REFERENCES
126
ANNEXES
1.
Drawing and photographs of the Pilot plant and Laboratory
129
2.
Description of the analytical methods
139
-50.
SUMMARY AND CONCLUSIONS
Although there is a vast number of wastewater treatment plants operating throughout the
world, it is a well-known fact that many of them don't meet the standards they were
designed for, particularly in plants treating mixed wastewaters (domestic and industrial).
The problems usually affecting the plants are influenced by the following basic factors:
sludge acclimatisation capacity to industrial wastes, flexibility and controlability of the
process, secondary settling performance and aeration capacity.
Knowing these, it was the purpose of the research to investigate a new process called
FMCT process (FMCT: food mass control technology) that is a new modification of the
activated sludge system. FMCT system includes a big settling tank which allows for
storage of biomass and control of F/M-ratio under varying load conditions. The new
process was supposed to provide the following advantages over the conventional system:
Better adjustment of biomass to instantaneous needs.
Reduction of aeration tank volume using concentrations of 5-8 g MLSS/1.
Reduction of energy consumption in aeration tanks.
Better quality of treated wastewaters.
Lower volume of excess sludge.
Lower probability of bulking problems.
A pilot plant study has been carried out in Galindo (Spain) primary treatment full scale
plant, treating mixed wastewaters (domestic and industrial) in two parallel lines, one
working with the CONV system and the other with FMCT system.
- 6-
Seven intensive study periods were carried out covering a range of temperatures: 8" C
to 2? C, and F/M-ratios: 0.15-0.60 (kg BOD/kg VSS.day).
A new mathematical model based on the IAWPRC activated sludge model no. 1 was
developped for the new system giving special attention to model the secondary settler.
The effluent quality found in both systems is well below the proposed EEC standards.
The soluble inert COD in the effluent is approximately 30-40 mg/1. Increasing F/Mratio increases soluble COD in the effluent having decreasing temperature a similar
effect.
Nitrification rates were low due to low pH and low alkalinity. Calculated nitrification
rates with IAWPRC activated sludge model no. 1 for pH-(7-7.5) were normal so no
additional inhibitory effects on nitrification was detected.
The yield is highly influenced by temperatures and F/M-ratio. For similar F/M-ratio the
yield at ffC was approximately twice the yield at 23° C.
The new system has proved to allow for better adjustment of biomass to instantaneous
needs due to storage of large amounts of biomass in the big clarifier. Other advantages
observed were: less occurrence of bulking and foaming problems, excess sludge volume
lower due to higher concentrations reached in secondary settler and sludge produced was
more stabilized with lower percentage of volatile suspended solids.
The mathematical model has shown to be a valuable tool for interpretation of
experimental results and for description of the actual settler performance and the
performance of the biological reactors.
INTRODUCTION
Bilbao is a coastal city in northern Spain which has about 1,000,000 habitants in
its drainage area. Sizable industry discharges its wastewaters to a severely polluted
estuary as well.
The "Consorcio de Aguas de Bilbao, Abastecimiento y Saneamiento" (CAGB), is
a public company owned by 24 municipalities.
Now the sewerage scheme in Bilbao is being developed and the wastewater
treatment plant of Galindo is in operation providing primary treatment to about
150,000 p.e. since July 1990.
The next stage in the scheme will be the construction of the biological treatment
in Galindo wastewater treatment plant as well as the construction of new sewers.
For that purpose a pilot plant was built in 1981 in order to investigate the
performance of biological treatment with the Bilbao wastewater. During the
period 1981-1987 several investigations were conducted in the pilot plant; resulting
in great experience to a Consorcio team that becomes specialised in biological
wastewater treatment processes as well as analytical methods.
Although there is a vast number of wastewater treatment plants operating
throughout the world, it is a well-known fact that many of them don't meet the
standards they were designed for. The problems usually affecting these plants are
influenced by five basic factors:
- sludge acclimatization capacity to industrial wastes;
- flexibility of the process;
- controllability of the process;
- secondary settling;
- aeration capacity.
-8-
The effects of deficiencies in these five areas produce the typical problems such
as:
- sludge bulking and flotation;
- scum production;
- inhibition caused by toxic agents;
- high consumption of electricity;
- poor performance in the treatment
Knowing these, it was the purpose of the Consorcio to investigate new designs and
operational strategies for biological treatment of mixed (domestic and industrial)
wastewaters. The new process to investigate was called FMCT process (FMCT:
Food to Microorganisms Control Technology). FMCT system includes a large final
settling tank which allows storage of biomass and control of F/M ratio under
varying load conditions. The new process was supposed to provide the following
advantages over the conventional system:
1. Better adjustment of biomass to the instantaneous needs.
2. Reduction of aeration tank volume using concentrations of 5 to 8 g/1 of mixed
liquor suspended solids.
3. Reduction of energy consumption in aeration tanks.
4. Better quality of treated wastewaters.
5. Lower volume of excess sludge.
6. More stable sludge with a lower proportion of volatile suspended solids.
7. Better sedimentation characteristics of the sludge with lower probability of
bulking problems.
To investigate the new process the pilot plant was modified having two parallel
lines one working with the Conventional (CONV) system and the other with the
FMCT system. The pilot plant was provided with cooling systems to carry out
experiments at low temperatures (8°C).
-9The investigation project was presented in the DG XII by the Consorcio de Aguas
de Bilbao and EVE (Ente Vasco de la Energia). Prof. Mogens Henze from the
Technical University of Denmark was in charge of developing a mathematical
model for the new system giving special attention to model the secondary clarifier.
During the investigation Prof. Peter Grau from the Prague Institute of Chemical
Technology became involved in the project giving valuable advice in activated
sludge population dynamics.
The pilot plant was installed in the Galindo wastewater treatment plant were it
was fed with mixed wastewaters (domestic and industrial). The experiments have
being performed during two years and finished in March 1991.
-102.
PILOT PLANT DESCRIPTION
As described in the previous chapter the plant is equipped with two lines or
processes which can be used in parallel. One of the lines is the conventional
completely stirred activated sludge tank followed by a traditionally sized final
clarifier, so called CONVentional process (CONV), while the other system has
much larger final clarifier. The system is called "Food to Microorganisms ratio
Control Technology" (FMCT). A flow diagram of the pilot plant is shown in
Figure 2.1.
The sewage treatment lines consist of the following:
- pumping of domestic sewage;
- mixing, homogenization and distribution to the two lines of both domestic and
industrial sewage;
- primary settling;
- biological reactor for activated sludge;
- secondary settling;
- sludge recirculation.
For the sake of completeness and for industrial waste composition purposes, the
following is available:
- incoming industrial waste storage tanks;
- means for homogenization, preparation and dosage of industrial wastes.
A detailed drawing of the pilot plant is included in Annex 1.
of secondary settler
recirculation capacity
AERATION TANKS AND SECONDARY SETTLER WERE THEfîMICAU.Y INSULATED
FOB LOW TEMPERATURE EXPERIMENTS
■at^Mg'-'»- ::...; / ' f t B g a i a s g s B B —
t=MC'r^ 2 - limali
12-
Fig. 2.2. GENERAL VIEW OF PILOT PLANT
Fig. 2.3. INDUSTRIAL WASTES STORAGE TANKS
- 13-
Fig. 2.4. AERATION TANK CONTROL METERS
äöaa _ .
**•' '
:
: *
I •• • •
wrosi» i ¿TU!
Fig. 2.5. PILOT CONTROL ROOM
-142.1.
Pumping of domestic sewage
In a well two submersible pumps are placed, one as a spare pump, of the
displacement type and protected by a bar screen for solids, hand-operated but
designed for self-cleaning.
The flow rate of each pump is 15 m 3 /h, the impulse pipe is made of
polypropylene, 1,000 m in length and 2.1/2" in diameter
and flows into a
homogenization chamber where an agitator mixes domestic and industrial wastes
adequately. Distribution to each line takes place through two weirs. The flow rate
to each unit is controlled.
Pumping characteristics
2.2.
No. of pumps
2
Unit flow rate
3/
15 m h
Power
5.5 kW
Type of runner
Displacement
Impulse piping
2.1/2" dia. Polypropylene
Primary settling
Each sewage treatment line is equipped with a primary settler 2.2 m in diameter,
made of steel plates and protected with epoxy paint.
The sewage flows in through a pipe into a central distribution well; it flows out by
gravity through a V-notched weir.
The bottom- is conical shaped, without scrapers, and the sludge is removed by
means of an automatic, programmed pneumatic valve.
- 15-
Primary settling characteristics
2.3.
Design flow rate
3 m3/h each settler
Diameter
2.2 m
Overflow rate
0.79 m/h
Total volume
12 m3
Biological reactor
Each line is equipped with a 18 m3 tank, where biological reactions take place.
Supply of oxygen is made by means of two blowers (one for each line), which
inject air into the reactor through fine-bubble ceramic diffusers.
Cooling coils are inside the reactors in order to enable carrying out tests at
temperatures lower than ambient temperature. The reactors are, therefore,
thermally insulated.
To prevent solids from settling when the airflowis low, each reactor is fitted with
a submerged propeller.
In each reactor tank, the pH, dissolved oxygen and temperature are continuously
controlled, the last two parameters acting automatically on the supply of air and
on the refrigerating equipment.
- 16
Biological reactor characteristics
2.4.
Volume
18 m3
Material
Steel plates, protected by epoxy paint
Design retention time
6h
Air injection flow
125 m3/h each blower
Thermal insulation
Expanded polystyrene
Temperature reduction
Vaporization coils
Secondary settling
The conventional line is equipped with a secondary settler 2.2 m in diameter,
made of steel plates; the FMCT line has a 4 m diameter settler, also made of steel
plates.
In both settlers sewage flows in through a central baffle well and overflows
through a V-notched weir.
The bottom is of conical shape; the 4 meter diameter settler was equipped with
a bottom scraper.
For low-temperature operation both settlers are insulated by means of a layer of
expanded polystyrene.
- 17-
Secondary settler characteristics
Conventional Line FMCT Line
2.2
4
0.79
0239
kg/(m2.h)
4.14
535
Thermal insulation
Expanded polystyrene
Diameter m
Overflow rate
m/h
Aplied solids flux
Total volume
2.5.
m3
12 m3
405
Sludge recirculation
The CONV line is equipped with two Mono rype pumps, capable of a variable
flow rate by means of frequency converters operated from the central panel.
The FMCT line has three pumps with the same features, whereby the recirculating capacity is increased.
There exists a continuous control on the flow of sludge which is being recirculated, with a direct reading on the panel.
Sludge recirculation characteristics
Conventional Line
No. of pumps
2
FMCT Line
3
Unit flow rate
0.6-4 m3/h
l-6m 3 /h
Recirculation rate
0.7-3 m3/h
2-12 m3/h
Flow rate variation
Frequency converter
- 182.6.
Incoming industrial wastewater reception
There is a set of 5 m3 m cylindrical tanks, made of glass-fibre reinforced
polyester, for the reception of concentrated industrial wastewaters.
Each tank contains a vertical mixer driven by a slow-speed .motor for the
homogenization of wastes received by tank trucks at variable intervals.
Each tank is fitted with a bottom-discharging valve through which a part of
each type of waste is removed to the 20 m3 joint preparation tank.
2.7.
Homogenization. preparation and dosage of industrial wastes
There is a homogenization and preparation tank where the various types of
industrial wastes are brought together, mixed and diluted. After preparation,
the whole mixture is transferred into another storage tank, whence it is finally
dosed, by means of a variable flow pumping unit, into the general inlet trough
where it is mixed with domestic sewage.
Both the preparation thank and the industrial waste dosage tank have a 20 m3
capacity.
-193.
METHODOLOGY
In the course of the research work, seven intensive study periods were carried
out under different operating conditions of the pilot plant.
In Periods 1 and 2 temperatures were maintained in the 14°C region (Winter).
In Period 3 the temperature was about 20°C (Spring).
In Periods 4 and 5 the temperature was kept in the 23°C region (Summer).
Finally, in Periods 6 and 7 (Winter) the cooling systems installed in the
aeration tanks were used, the temperature being kept at about 8°C. Ambient
temperature during the latter periods was 10-12°C.
At each temperature two different conditions of F/M ratio were tested.
In between the various intensive periods there were transition periods in which
the pilot plant was stabilized to the specific operating conditions which were
subsequently maintained during the next intensive period.
3.1.
Research schedule
Period 1: 16-19 Jan. '90
Temperature approx. 13°C
CONV. Line
F/M = 0.376
FMCT Line
F/M = 0.275
Period 2: 26 Feb-26 Mar '90
Temperature approx. 16°C
CONV. Line
F/M = 0.405
FMCT Line
F/M = 0.174
-20
Period 3: 16-30 May. '90
F/M = 0.845
FMCT Line
F/M = 0.22
Period 4: 9-24 Jul '90
Temperature approx. 23°C
CONV. Line
F/M = 0205
FMCT Line
F/M = 0.162
Period 5: 20 Aug-3 Sep '90
Temperature approx. 23°C
CONV. Une
F/M = 0.4
FMCT Line
F/M = 0.282
Period 6: 14-31 Jan '91
Temperature approx. 8°C
CONV. Line
F/M = 0.231
FMCT Line
F/M = 0.207
Period 7: 18 Feb-8 Mar '91
3.2.
Temperature approx. 19.5°C
CONV. Line
Temperature approx. 8°C
CONV. y ne
F/M = 0.579
FMCT Line
F/M = 0.429
List of sampling points and general sampling strategy
For identification of the sampling points, the following codes have been used:
First character Identifies the treatment line.
C:
CONV
U:
FMCT
-21 Other characters: Identify the location of the sampling point.
TJWO: domestic sewage
IWO: industrial waste
SPO:
influent into plant - domestic and industrial mixture
SPI
effluent from primary settling
SP2;
contents of aeration tank
SP3
effluent from aeration tank
SP4:
effluent from secondary settling
SP5
re-circulated sludge from secondary settling
SP6:
sludge from mixed liquor
SP7:
sludge removed from primary settling
Sampling points scheme is shown in figure 3.1
Types of samples taken are as follows:
Type 1: composite - 24 hours (500 ml samples taken hourly)
Type 5: grab taken at 9:00 hrs
Type 6: grab taken at 17:00 hrs
Type 7: grab taken at 01:00 hrs
Both during the intensive and transition periods, the following samples were
taken on a daily basis:
1) SPO:
composite sample from 24 hrs, influent to pilot
plant.
2) CSP1 and USP1:
composite sample from 24 hrs, effluents from the
primary settling.
3) CSP4 and USP4:
composite sample from 24 hrs, final effluents.
4) CSP2 and USP2:
3 grab samples daily (9hrs, 17 hrs and 01 hrs),
mixed liquors.
FIG. 3.1: SAMPUNG POINTS
PILOT PLANT
LINE CONV
AER AVON
TANK
MIXING TANK
RECIRCULACtON
-»
—
EFFLUENT
WASTED
SP.)
...LINE FMCT
—
RECIRCULAVON
—
SLUDGE
EFFLUENT
WASTED
SLUDGE
IW2 1
INDUSTRIAL
PI
f IW3
WASTE
L^^_^
DOSING
INDUSTRIAL
TANK
WASTE
MIXING TANK FOR
INDUSTRIAL
WASTE
DOMESTIC WASTE
IW5 J
I IW6
-23-
5) CSP5 and USP5:
3 samples daily (9 hrs, 17 hrs and 01 hrs) of recirculated sludge.
At the end of each intensive period, additional samples were taken:
6) CSP7 and USP7:
Grab sample of primary sludge at 9 hrs.
Sampling was done manually, by the plant operators in all cases, except for
variability studies, when samples were taken by automatic samplers.
Upon completion of the last two intensive periods, a special sampling was
made to define the varying conditions in the pilot plant. This sampling was
carried out by taking samples every 2 hours for a 24 hours period, each
individual sample being independently analyzed.
The analyzed sampling points were as follows:
CSP1: effluent from primary settling, CONV line
USP1: effluent from primary settling, FCMT line
CSP4: effluent from secondary settling, CONV line
USP4: effluent from secondary settling, FCMT line
CSP3: effluent from aeration tank, CONV line
USP3: effluent from aeration tank, FCMT line
CSP5: re-circulated sludge, CONV line
USPS: re-circulated sludge, FCMT line
-243.3. List of analyzed parameters
The following groups are distinguished:
Group 1. General parameters
TSS
Total Suspended Solids (mg/L)
VSS
Volatile Suspended Solids (mg/L)
CODT
Total Oxygen Chemical Demand (mg 02/L)
CODS
Soluble Oxygen Chemical Demand (mg 02/L)
BODT
Total Oxygen Biochemical Demand (5 days) (mg 02/L)
BODS
Soluble Oxygen Biochemical Demand (5 days) (mg 02/L)
TKNT
Kjeldahl Total Nitrogen (mg/L)
TKNS
Kjeldahl Soluble Nitrogen (mg/L)
NH4-N
Ammonia Nitrogen (mg/L)
N03-N
Nitrate Nitrogen (m'g/L)
ALCALT Total Alkalinity (mmol HC03-/L)
P TOT
Total Phosphorus (mg/L)
P04-P
Dissolved Orthophosphate P (mg/L)
SULF T
Total Sulfides (mg/L)
CL"
Chlorides (mg/L)
O&G
Oils and Greases (mg/L)
Group 2. Special parameters
Phenols
Deterg.
Phenols (mg/L)
Anionic Detergents (mg/L)
CN-T
Total Cyanides (mg/L)
Ca T
Total Calcium (mg/L)
Mg T
Total Magnesium (mg/L)
-25
Cd T
Total Cadmium (mg/L)
Cr T
Total Chromium (mg/L)
Cu T
Total Copper (mg/L)
Ni T
Total Nickel (mg/L)
Pb T
Total Lead (mg/L)
Zn T
Total Zinc (mg/L)
As T
Total Arsenic (mg/L)
Hg T
Total Mercury (mg/L)
Group 3. Specific analyses of sludge
TSS
Total Suspended Solids (mg/L)
VSS
Volatile Suspended Solids (mg/L)
SVI
Sludge Volume Index (ml/g)
ESP. GRAV.
Specific Gravity
ISV
Initial Settling velocity (cm/min)
SV
Volume Settled Within 30 min (ml/L)
OUR
Oxygen uptake Rate (mg O^L. h)
SOUR
Specific Oxygen Uptake Rate (mg 0 2 /g.h)
H. BLANKET
Sludge Blanket Height (m)
MICROSCOPIC Examination
Analyses Schedule During Intensive Periods
On sewage samples: Type 1 (composite from 24 hrs)
-26
1
1 Frequency
1 Daily
| Three times
| per week
SPO
i
CSP1 | USPl
CSP4
TSS
CODT
BODT
TKNT
USP4 |
1
NH4-NI
VSS
CODS
BODS
TKNS
N03-NI
P04-P
Al cal
P TOT
Cl
0 &G
Ca
Fe
Pb
Phenols
Mg
Zn
Mn
Deterg.
Cu
Ni
Hg
Sulfides
Cr
Cd
Cyanides
On sludge samples: Types 5, 6 and 7 (grab samples, taken at 9, 15 and 01 hrs)
27 -
I
SP2-5 ¡SP2-6¡SP2-7¡SP5-5¡SP5-6¡SP5-7¡
1
i
|
|
i
I
i
TSS
|
I
i
SV
I
Blanket H
-
i
i
i
SP7
VSS
|
|
|
i
1 Daily
|
|
¡ Sp. Gr.j
| ISV
|
| OUR
|
|
¡Twice
|per Week
¡ Micro. ¡
| Anal
j
¡
j
|
|
¡Only Once,¡Ca
¡at the End¡Cu
¡of each
¡Fe
¡Intensive ¡Zn
¡Period
¡Pb Mn
|
Mg¡
Cr¡
Ni¡
Cd|
Hg¡
¡
i
|
|
i
i
|
|
|
|
|
i
l
¡
¡
|TSS VSS|
¡Ca
Mg¡
¡Cu
Cr¡
¡Fe
Ni¡
¡Zn
Cd|
¡Pb Mn Hg¡
During transition periods
During the transition periods the same analysis with the same frequency were
carried out as during the intensive periods, except for the sewage samples,
were the following parameters were omitted: CODs, BODg, TKNS and P
TOT. During the transition periods no samples were taken in SP7.
3.4. List of parameters measured in the plant on a continuous basis
All continuous measurement signals were received at a data acquisition unit
connected to an IBM PC computer, where they were processed by means of
the software Labtech. Notebook, the configuration of which enabled the data
-28-
to be instantaneously transmitted from each meter to the printer every 15
minutes; thus, a daily printout with 96 entries was produced. The data printed
every 15 minutes; represent the average value of all signals received during
such a period of time. Summary printouts were also produced daily, listing
the maximum, average and minimum values for each meter, as well as the
total values.
Parameters measured on a continuous basis are as shown below:
Instantaneous Measurements
1. Flow Rates
FI-1
FI-2
FI-3
FI-3'
FI-4
FI-4'
FI-5
FI-5'
Domestic sewage Influent
Industrial influent
Influent to the CONV line
Influent to the FMCT line
Sludge recirculation - CONV line
Sludge recirculation - FMCT line
Air to aeration tank - CONV line
Air to aeration tank - FMCT line
2. Temperatures
TI-1
TI-2
TI-2'
TI-3
TI-3'
Mixing tank for domestic sewage and industrial waste
Mixed liquor - CONV line
Mixed liquor - FMCT line
Secondary settler - CONV line
Secondary settler - FMCT line
3. pH
PHI-1
pHI-2
pHI-2
pHI-3
pHI-3'
Mixing tank for domestic sewage and industrial waste
Mixed liquor - CONV line
Mixed liquor - FMCT line
Secondary settler - CONV line
Secondary settler - FMCT line
294. Dissolved Oxygen
OIC-1
OIC-1'
Mixed liquor - CONV line
Mixed liquor - FMCT line
Totalized measurements
1. Flow Rates
FQ-1
FQ-2
FQ-3
FQ-3'
FQ-4
FQ-4'
FQ-5
FQ-S'
Domestic sewage influent
Industrial influent
Influent to the CONV line
Influent to the FMCT line
Sludge recirculation - CONV line
Sludge recirculation - FMCT line
Air to aeration tank - CONV line
Air to aeration tank - FMCT line
2. Power Input
Ul
U2
U3
U4
US
Blowers - CONV line
Recirculation pumps - CONV line
Blowers - FMCT line
Recirculation pumps - FMCT line
Recirculation pumps - FMCT line
3.5. Total number of samples and analysis
Research work covered a total of 610 days, split in 489 days of transition
periods and 121 days of intensive periods. The number of samples processed
during the transition periods is estimated at 8,313, on which 55,743 parameters were analyzed; during the intensive periods some 2,071 samples were
taken and a total of 16,397 parameters analyzed.
Therefore, the total number of samples taken during the investigation was
10,384, on which 72,140 parameters were analyzed.
-303.6. Scientific and technical team
Miguel Lueje (CAGB - Mechanical Engineer)
Alejandro de la Sota (CAGB - Biologist)
Alberto Gómez (CAGB - Assistant Mechanical Engineer)
Prof. Peter Grau (Scientific Consultant, President of IAWPRC)
Prof. Mogens Henze (Technical university of Denmark, Modelling Expert)
René Dupont
(Technical University of Denmark, Modelling Expert)
Analytical Control
Karmele Zaballa (Biologist)
Juan M' Cenigaonaindia (Chemist)
Cristina Arrieta (Chemist)
José Antonio González (Chemical Technical Engineer)
Itziar Unzueta (Biologist)
Roberto Colino (Biologist)
Ma Jesus Citores (Chemist)
Marian Bilbao (Chemical Technical Engineer)
Itziar Aretxabala (Chemical Technical Engineer)
Pilot Plant Operation
Luis Angel Bilbao,
Coordinator (Merchant Navy Chief Engineer)
Ricardo Gómez (Electronics Technician)
Rafael López Heredia (Electronics Technician)
Antonio Malave (Electrical Technician)
Vicente Carro (Mechanical Technician)
An tol in Trancho (Electronics Technician)
Francisco Gutiérrez (Electrical Technician)
Esteban Garcfa (Electronics Technician)
Iñaki Zorrilla (Energetic Efficiency Technician)
31
3.7. Analytical Methods
All analytical methods employed conform to "Standard Methods for Sewage
Analysis", 17th Edition, 1989.
The analytical methods used are listed hereunder.
3.7.1. General Parameters
TEMPERATURE
pH
DISSOLVED OXYGEN
TOTAL SOLIDS
TSS
VSS
CODT
CODs
BODT
BODs
TKNT
TKNS
NH4-N
NO3-N
ALKALINITY
PTOTAL
P04-P
SULPHATES
TOTAL SULPHIDES
CHLORIDES
OILS & GREASES
Meter installed in the plant
Meter installed in the plant
Meter installed in the plant
Evaporation and drying at 105°C. Gravimetry
Filtering through glass fibre. Drying at 105 °C.
Gravimetry
Filtering. Ignition at 550°C. Gravimetry
Open reflux method. Oxidation by potassium
dichromate for two hours.
Membrane filtering. Two hours of open reflux
Dilution method. Dissolved oxygen
readings through probe
Membrane filtering. Dilution method
Acid digestion. Distillation and ammonia analysis.
Membrane filtering and application of the abovenamed method
Nessler colorimetrie method
Chromotropic acid method
Neutralization at Ph = 3.7
Acid digestion, orthophosphates analysis
Vanadate-Molybdate method.
Precipitation with barium salts. Gravimetry
Precipitation. Filtering and titration with sodium
thiosulphate
Titration with silver nitrate
Extraction by freon. Evaporation and
gravimetry.
3.7.2. Special Parameters
PHENOLS
Distillation and colorimetry of distillate with 4aminoan tipyrine. Prior extraction with chloroform.
-32
ANIONIC DET.
TOTAL CYANIDES
TOTAL METALS
Standard LAS. Colorimetry with methylene blue.
Distillation in acid medium. Selective electrode
method
Digestion by nitric acid. Analysis of metals by means
of atomic absorption spectrophotometry.
3.7.3. Sludge Analysis
TSS
VSS
SET. VOLUME
SPEC. GRAV.
ISV
OUR
BLANKET HEIGHT
MICR. ANALYSIS
Filtration through glass fibre. Drying at 105°C.
Gravimetry.
Filtration. Ignition at 550°C. Gravimetry
30-minute settling in a 1-litre cylinder.
Gravimetry
Settling curve in a 2-litre graduated cylinder
Probe measurement of the oxygen decay rate in a
BOD bottle
Height in meter from the bottom of the settling tank
to the interphase between the settled sludge and the
supernatant.
Observation of sludge under the microscope. GRAM
and NEISSER staining.
-334.
OPERATING STRATEGY
The plant has been treating a mixture of domestic sewage and industrial
waste of the following constant ratio:
85% by volume - domestic
15% by volume - industrial
The industrial waste was prepared from concentrated pickling liquors. The
final mixture had a concentration of approx. 20 ppm iron. Iron was the
component with the highest concentration in the industrial waste that was
handled.
Pumping facilities for the domestic sewage were located in a municipal
collector at Sestao, from August 1989 till June 1990. Pumping was continuous
from 06 hrs to 22 hrs; there were conditions of intermittent pumping during
the night due to the low flow rate of the collector, aggravated by the drought
and the water supply restrictions that prevailed in the district during that
time.
From June 1990 till the completion of the Project, the pumping facilities were
located at the Galindo Treatment plant, pumping being constant 24 hours a
day ever since.
Control and operation of the plant was carried out, throughout the project, by
the responsible technical personnel, 24 hours per day, 7 days per week.
The start-up of the pilot plant, prior to the formation of biomass in the
aeration tanks, was based on domestic sewage. During that time, operating
conditions in both lines were maintained as follows: 3 m3/h influent rate,
100% recirculation and dissolved oxygen levels of 2.5 mg/L.
-34-
Once sufficiently high concentrations of MLSS were reached, the
acclimatization phase for industrial waste was initiated. Industrial waste was
prepared from pickling liquors with high acidity and metal concentration
(HCl-Fe and H2S04-Cu-Ni).
This mixture was diluted with clean water and mixed prior to entering the
plant, with no previous neutralization. The concentration was increased by
10% daily, until 100% was dosed in ten days time.
Once 100% of industrial waste was reached in the mixture to be treated, a
considerable deterioration of the effluent was observed and it was, therefore,
decided to neutralize the industrial waste at Ph = 7 prior to the treatment.
The pre neutralization was effected with NaOH.
Influents treated in each line were:
2.5 m3/h
0.5 m3/h
Total
= 3.0m3/h
Domestic sewage
Industrial waste
Mixture
From that moment on, the operating strategy can be divided into two parts,
depending on the fundamental parameter of the process control selected:
Control Parameter: Sludge Age (9x)
Control Parameter: Mass Load ratio (F/M)
4.1. Control Parameter ; Sludge Age (8x1
Operation criteria for periods 1, 2 and 3.
As operating conditions we considered: dissolved oxygen, the recirculation
rates and wasting rates.
-354.1.1.
Conventional line
Dissolved Oxygen
The D.O. concentration in the aeration tank was kept at a preset value, 1.5
mg/L, by means of an oxygen controller which receives a signal from a meter
of the electrode probe type which, depending on the set point, actuates a
speed variator which regulates the blowers, which respond to changes in the
dissolved oxygen. The blowers increase or decrease the air supply to the
aeration tank.
Recirculation Rate
Departing from the result of the 30-min settling test, the recirculation rate to
be applied was calculated as follows:
Qr
SV
Qi
1000 - SV
where: Qr
x 100
(4.1)
Recirculation flow
Qi
Influent flow
SV
Settled volume after 30 minutes.
Figure 4.1 can be used to calculate the recirculation rate as a function of the
settled volume.
Wasting rate
When the sludge age established in each case is known, the wasting rate
needed to maintain the sludge age constant is calculated as follows:
Fig.4.1.Chart for calculation of recycle
flow as a function of settled volume
test.
Recycle (low (%)
GO
O)
150
200
250
300
Settled volume (SV ml/L)
350
400
450
500
37Va
SSe. Qi
Øx
MLSS
Qw =
where: Qw
v innn
i A 'M
Wasted flow (l/d)
Va
Volume of aeration tank (m3)
Gx
Sludge age (d)
SSe
Total suspended solids in effluent (kg/m3)
Qi
Influent flow (m 3 /d)
MLSS
Total suspended solids in mixed liquor (kg/m3)
Wasting was carried out intermittently from the mixed liquor.
Another factor which was taken into account when carrying out the
recirculation rate and wasting operations was the height of the sludge blanket
in the secondary settling tank which, occasionally, due to bad settling
characteristics of the sludge, rose to the extent that it caused loss of solids
into the effluent. To preserve the characteristics of the effluent, the option
was taken to increase the rate of recirculation by an additional 50% for two
hours, with a maximum limit of 4.5 m3/h, and to waste 1 m3 of mixed liquor.
4.1.2. FMCTLine
Dissolved Oxygen
D.O. in the aeration tank was controlled automatically in the same way as in
the conventional line and kept at a level of 2.5 mg/1.
-38Recirculation rate
Initially, the recirculation rate was adjusted three times per day, calculations
being made according to the above formula (4.1). Later, recirculations in the
40 - 60% range were effected and, finally, recirculation rate charts were used,
calculated as a function of the variation in the total organic load. Adjustment
took place every hour.
One of the charts used is shown in Figure 4.2.
Wasting rate
Wasting was taken from the mixed liquor three times a day, at 8 h intervals,
calculated as per formula (4.2). Each wasting was 1/3 of the total daily waste.
To facilitate calculations, individual charts for each sludge age were designed,
wherein the wasting rate is given as a function of the total suspended solids in
the effluent and the total suspended solids in the mixed liquor.
One example is shown in Figure 4.3
42.
Control parameter : Mass load ratio (F/MÌ
It was the operating criteria during periods 4, 5, 6 and 7. Control was the
same for both lines. The operating parameters considered in this case are:
dissolved oxygen, influent flow rate, recirculation rate and sludge wasting.
Fig.4.2.Recycle flow curve used in FMCT
line for periods 2 and 3.The curve fo
llows the CODi variation in 24 h.
Reoycle Flow (%)
00
—
80-
—
......
60-
•
■
•
1
40-
\
i
v
........
■■.
\
20-
o-
1
1 —
i
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Hours
Fig.4.3.Chart for calculation of wasting
flow as a function of MLSS and TSSe for
0a-2O days.
300
250
200-
15010050-
Qw (L/8 hours)
-—
SSe-10ppm
-+-
SSe«20ppm
-*-
SSe-30ppm
-B-
SSe-40ppm
-K-
SSe-50ppm
-e-
SSe-60ppm
-A
SSe-70ppm
-S-
SSe-80ppm
o
-41 Dissolved Oxygen
The set point for CONV line = 1.5 mg/1, FMCT line = 2.5 mg/1, being
established, this was maintained automatically as described above. Higher DO
in FMCT line was selected to provide sufficient concentration gradient of
oxygen for the higher MLSS.
Influent Flow Rate
After establishing the F/M ratio to be maintained during the period under
consideration, the influent flow rate was calculated daily, depending on the
volatile suspended solids 'in the mixed liquor and the chemical oxygen
demand of the influent, by applying the following formula:
F/M . MLVSS . Va
Qi =
BOD
(4.3)
BOD = 0.44 COD
where: Qi
BOD
Influent flow (m3/d)
Biochemical oxygen Demand (kg/m3)
MLVSS Volatile suspended solids in mixed liquor (kg/m3)
Va
Aeration tank volume (m3)
COD
Chemical Oxygen Demand (kg/m3)
This is displayed in Fig. 4.4.
Recirculation rate
This was adjusted as high as necessary, to prevent sludge from floating in the
secondary settling tank as a result of de-nitrification. During low-temperature
periods, when these flotation problems did not occur, the recirculation rates
were smaller, about 50%.
Fig.4.4.Chart for calculation of in
fluent flow as a function of MLVSS
and CODi for F/M ■ 0.5
Ql (m3/h)
■Iß—,
1D
141210-
I
—*— C O D - 3 0 0 mg/l
-4-
C O D - 3 5 0 mg/l
-*-
C O D - 4 0 0 mg/l
-B-
C O D - 4 5 0 mg/l
-*-
C O D - 5 0 0 mg/l
~~r^\
Ä—*
8-
^^^"^
\
\
6- -
<£~*<Z^ fr__
4j
^
"
*
^
^
^
"
*
"
"
^
—
2-
o500
1000
1500
2000
2500
3000
MLVSS (mg/l)
3500
4000
4500
5000
-43Wasting rate
Wasting were carried out depending on the height of the sludge blanket in
the secondary settler.
During high-temperature periods (4 and 5), limits of 3.2 m for the CONV
line and 3.7 m for the FMCT line were established.
Considering that the concentration of total suspended solids in the effluent
was too high with respect to good sludge settling characteristics during hightemperature periods and on the assumption that this might be due to
excessive blanket height, the decision was made to decrease it; for lowtemperature periods (6 and 7) the limits were set at 2 m. for the CONV line
and 3.5 m. for the FMCT line.
-44RESULTS
In this chapter are included all the average results for each intensive period.
This results are discussed later in chapter 7.
45
TABLE 5.1.
OPERATING CONDITIONS IN INTENSIVE PERIODS
TABLE 5.2.
HYDRAULIC DATA
TABLE 5.3.
INFLUENT TO PILOT PLANT (Domestic & Industrial)
TABLE 5.4.
METALS IN INFLUENT TO PILOT PLANT (Domestic & Industrial)
TABLE 5.5.
PRIMARY CLARIFIERS EFFLUENT CSP1/USP1
TABLE 5.6.
METALS IN PRIMARY CLARIFIERS EFFLUENT CSP1/USP1
TABLE 5.7.
FINAL EFFLUENTS CSP4/USP4
TABLE 5.8.
METALS IN FINAL EFFLUENTS CSP4/USP4
TABLE 5.9.
DIURNAL VARIATIONS CONVENTIONAL SYSTEM
TABLE 5.10.
DIURNAL VARIATIONS FMCT SYSTEM
TABLE 5.11.
ACTIVATED SLUDGE MASS BALANCE (1)
TABLE 5.12.
ACTIVATED SLUDGE MASS BALANCE (2)
TABLE 5.13.
SLUDGE QUALITY
TABLE 5.14.
METALS IN PRIMARY SLUDGE CSP7/USP7
TABLE 5.15.
METALS IN ACTIVATED SLUDGE CSP2/USP2
TABLE 5.16.
AERATION PARAMETERS
TABLE 5.17.
ENERGY CONSUMPTION
TABLE 5.18.
SLUDGE AGE CALCULATION
TABLE 5.1: OPERATING CONDITIONS IN INTENSIVE PERIODS
PERIOD
DATE
FA< (kgBOtVkgMLVSS.day)
1
2
16-29 Jan 90 26Feb-26Mar 90
CONV
FMCT
FMCT
CONV
3
16-30 May 90
CONV
FMCT
4
9-24 Jul 90
FMCT
CONV
5
20Aug-3Sep 90
CONV
FMCT
6
14-31 Jan 91
CONV
FMCT
7
18Feb-8Mar91
CONV
FMCT
0,376
0.275
0,405
0.174
0,645
0,22
0.205
0,162
0,4
0.2S2
0,231
Temperature (deg C)
12,9
13.2
15.6
16.4
19.3
19.7
20.6
20,5
22,7
22.6
11.6
8.6
6.4
6.1
Primary aettllng
Yes
Yes
Yes
Yes
No
No
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Influent flow (Ql) (m'/h)
1.51
3.44
5.9
6.2
2.56
3.14
1.76
6.58
0,207
0.579
0.429
2.53
2.54
2.07
2
2.S
2,3
Recycle flow (Or) (m'/h)
1.91
1.54
1.59
1.56
1,56
6,39
3
9
1.77
4.76
1.26
1.57
1.11
3.29
D.O. (mg/l)
0,97
2.65
1.6
2.07
1.64
1,56
1.53
2.5
1.4
1.4
1.63
2.65
1.93
2.51
1.6
No Detec
1.3
1.5
1.7
1.8
2.9
1.8
3.3
Blanket level (m)
2.1
1.4
2,5
3.1
2.9
pH
7,4
6.8
7.4
7,3
7.4
6.2
6.3
6.2
6.6
6.8
7.4
7.3
7.5
7.2
Total sludge age (daya)
9,6
11.5
6.7
47.4
4.2
27.1
36,8
31,4
10.0
19,7
12.0
.44.4
4.6
13.6
2642
3630
2194
5091
1420
5009
1097
3708
3136
5606
2346
3067
650
3616
MLVSS (mo/I)
Recycla VSS (mg/n
6912
10621
5062
11450
3470
7804
2400
5500
12485
16860
6324
8963
2032
9356
U (KgBOO/kgVSS.day) (1)
0.318
0.254
0.36
0,166
0.795
0,2
0,165
0,153
0.375
0.26
0.22
0.193
0.534
0.392
Sludge wasted (kgVSS/day) (2)
2.036
0.17
6.972
0.789
6
0,702
0
0
0
0
5.416
1.989
3.582
13.43
Effluent sludge (kgVSS/day) (3)
4.752
1.987
1.63
1.273
2.467
3.651
0.7
1,676
4.674
5.335
0.614
0.511
0.349
1.607
Sludge wasted and lost (4)
(KgVSS/day)
6.767
2,157
8.602
2.061
10.467
4.353
0.7
1.876
4.874
5.335
6.031
U
3.931
15.237
0.83
0.B1
0.80
0.76
0.82
0.75
0,79
0.75
0.75
0.73
0.66
0.62
0.73
0.65
MIVSS/MLSS
UUzatlon rata (kg BOO removed/kg MLVSS.(Jay)
Sludge wasted - OwJCa
Effluent sludge • (QI-Ow).VSSe
Sludge wasted and lost - (Ow.Xa) ♦ (QH}w).VSSa
TABLE 5.2: HYDRAULIC DATA
PERIOD
DATE
2
1
16-29 Jan 90 26Feb-26Mar 90
CONV
FMCT
CONV
FMCT
3
16-30 May 90
CONV
FMCT
4
9-24 Jul 90
CONV
FMCT
5
20Aug-3Sep 90
CONV
FMCT
6
14-31 Jan 91
CONV
FMCT
7
18Feb-BMar91
CONV
FMCT
a (domestic ♦ lndustriai)(m'/1i)
2.53
2,54
2,07
2
2,5
2,3
1.51
3.44
5,9
6,2
2.56
3,14
1,76
6.58
Q Industrial (m'/h)
0.37
0.36
0.31
0.31
0,33
0.31
0.19
0,45
0.24
0.34
0.31
0,39
0.14
0,54
Overflow Rate P.S. (m/h)
0.66
0.66
0.55
0,55
0.39
0,9
1.55
2.15
0.67
0.62
0.46
1.73
Retention Time P.S. (h)
4.35
4.33
5.24
5,24
7.29
3.2
1.66
1.34
4,3
.3.5
6.18
1.67
Retention Time A.S. (h)
4,05
4,41
4,67
4,91
4.43
2.7
3.99
1.44
2.34
1.38
4.66
3.62
6,22
1.62
Overflow Rate S.S. (m/h)
0,66
0,2
0,55
0,16
0,65
0,16
0,39
0,27
1,55
0.65
0,67
0,25
0,46
0,52
Retention Time S.S. (h)
4,35
15.93
5.24
19.27
4,4
17,59
7,29
11,76
1.66
4,93
4,3
12.66
6,16
6,15
Solids Surface Load S.S.
(kg/m'.h)
3,62
1,41
2,67
1,95
1.65
4,6
1.65
4,9
6.17
7.76
3.62
1.91
0,64
4.15
2,1
1.4
2,5
3.1
2,9
1.6
No detec
1,3
1.5
1.7
1.6
2,9
1,6
3,3
1.91
1,54
1,59
1,56
1,56
6,39
3
9
1.77
4,76
1,26
1,57
1,11
3.29
Blanket level (m)
<» (m'/h>
P.S.
Primary Settler
A.S.
Activated Sludge
S.S.
Secondary Settler
Or
Recirculation flow
TABLE 5.3: INFLUENT TO PILOT PLANT (Domestic & Industrial)
PERIOD
DATE
2
1
16-29 Jan 90 26Feb-26Mar 90
3
16-30 May 90
4
9-24 Jul 90
S
20Aug-3Sep 90
6
14-31 Jan 91
7
18Feb-8Mar 91
SS (mg/l)
262
343
237
232
260
250
319
VSS (mg/l)
217
260
190
150
177
169
213
B005T(mg/t)
386
375
377
194
234
207
236
148
146
166
35,5
44,9
63
70.3
COO T (mg/l)
1000
622
717
409
508
422
562
COD S (mg/l)
323
330
109,4
127
156
156
TXNT(mg/I)
90.1
61
34,5
34,3
43,9
483
TKN S (mg/l)
74.3
70
23,5
23.5
34,9
37.7
N-NH, (mg/l)
70.6
72.4
63.4
24,4
23.9
30,2
32
N-NO, (mg/l)
0.5
0.3
0.4
0,2
0.2
0,4
0.3
11.4
10,4
14.2
6,1
5.6
5.5
5,8
7.0
9.1
13.2
5.4
5.3
2.5
3.8
8.46
6.46
7.72
4.62
5,98
4,76
4.32
56.3
28,5
51.6
32.3
54,5
B005 S (mg/1)
TOTAL P (mg/l)
P-PO. (mg/l)
ALKAUNITY (mmol/HCO,-)
96
OIL l OREASE (mg/l)
173
66,6 '
SULFIDE (mg/l)
1.5
1.9
2
1.2
1.8
1
1.3
CHLORIDE (mg/l)
142.5
143
91.9
407.6
445.3
233.6
487.9
PHENOLS (mg/l)
0,05
0,043
0,013
0.011
0,052
0.186
SURFACTANTS (mg/l)
12.S
14.4
7.2
8.9
6.8
11.1
CYANIDE T (mg/l)
0.S2
0,178
0.139
0.052
0.15
0.19
14.4
Average values In every period.
CO
TABLE 5.4: METALS IN INFLUENT TO PILOT PLANT (Domestic & Industrial)
PERIOD
DATE
1
2
16-29 Jan 90 26Feb-26Mar 90
3
16-30 May 90
4
9-24 Jul 90
5
20Aug-3Sep 90
6
14-31 Jan 91
7
18Feb-8Mar 91
CaT(mg/l)
50.6
46.1
37,6
72.6
92.2
97.2
129
Mg T (mg/1)
7.4
7,3
5,9
23.1
36.4
24.1
49,3
Cd T (mg/l)
0.003
0,003
0,003
0,002
0.005
0.004
0.004
Cr T (mg/1)
0,049
0.04
0,023
0,045
0,031
0.013.
0,015
Cu T (mg/l)
0.069
0.072
0,065
0.097
0,074
0.06
0,069
Fe T (mg/l)
20
19.6
6.5
24,9
23,5
19
17.3
Mn T (mg/l)
0.191
0.169
0.1
0.239
0.247
0.234
0.233
NI T (mg/l)
0,129
0.126
0.O97
0.131
0,07
0.125
0.091
Pb T (mg/1)
0.076
0,075
0,072
0.09
0,102
0.079
0.075
Zn T (mg/l)
0.257
0,221
0.274
0.25
0.277
0.202
0.126
Average values in every period.
4*
CO
TABLE 5.5: PRIMARY CLARIFIERS EFFLUENT CSP1/USP1
PERIOD
DATE
1
2
16-29 Jan 90 26Feb-26Mar 90
CONV
FMCT CONV
FMCT
3
16-30 May 90
CONV
FMCT
4
9-24 Jul 90
CONV
FMCT
5
20Aug-3Sep 90
CONV
FMCT
6
14-31 Jan 91
CONV
FMCT
7
18Feb-8Mar 91
CONV
FMCT
SS (mg/l)
179
194
63.6
109
133
132
138.2
139.3
158
177
VSS (mg/l)
141
151
63.7
62,8
96.6
99.6
99.3
100.1
113
123
B0O5 T (mg/l)
295
316
114
133
159
143.5
159.1
153.1
161
174
BOOS S (mg/l)
144
145
41
43
57.8
45.5
63.6
63
83
73
COD T (mg/l)
640
674
256
285
326.6
322.4
331.3
341.1
406
418
COD S (mg/l)
29a
116
111
137
139
137.5
140
171
166
TKN T (mg/l)
79
65.2
30.1
30
33.2
33
39.9
39.8
46.6
43.3
TKNS(mg/l)
67
23.6
23.6
26
24.5
33,7
33.5
37.6
36.3
N-NH, (mg/l)
66.4
24.5
23,4
25.2
24,8
29.7
26.4
32.8
30.6
0,4
0.1
0,3
6
5.6
66.1
0.3
0.2
0.2
0,2
0.21
0.16
0,3
TOTAL P (mg/l)
11.4
10.1
6.9
6.7
5,8
5,7
5.1
4,9
P-PO, (mg/l)
11.9
10
5.6
S.5
S.9
S.5
2.7
2,6
4.9
4.1
4.24
519
N-NO, (mg/1)
ALKAUNrTY (mmol/HCO,)
7.76
6.12
OIL t, GREASE (mg/l)
56,9
51.9
1.7
2.1
133.9
132
SURFACTANTS (mg/l)
11.8
14.3
CYANIDE T (mg/l)
0.37
0.22
SULFIDE (mg/l)
CHLORIDE (mg/l)
PHENOLS (mg/l)
Average values In every period.
4.52
4.32
6.16
5.22
4,6
4,56
4,42
295
363
423
381
217
207
438
TABLE 5.6: METALS IN PRIMARY CLARIFIERS EFFLUENT CSP1/UPS1
PERIOD
DATE
Ca T (mg/))
2
1
16-29 Jan 90 26Feb-26Mar 90
CONV FMCT CONV FMCT
41.7
3
16-30 May 90
CONV FMCT
4
5
9-24 Jul 90 20Aug-3Sep 90
CONV FMCT CONV FMCT
6
14-31 Jan 91
CONV FMCT
7
18Feb-8Mar91
CONV FMCT
41.8
Mg T (mg/l)
6.6
6.6
Cd T (mg/I)
0.003
0,002
Cr T (mgfl)
0.019
0,026
0,009
0.013
0,016
0.018
0.006
0.005
0.008
0,008
0.03
0,037
0,037
0,039
0.039
Cu T (mg/I)
0,036
0,046
0.026
0,032
0.031
Fe T (mg/1)
6.6
6.9
5,6
9
9.1
10.5
7.19
7.32
6,41
6.93
Mn T (mg/I)
0,125
0.105
NI T (mg/I)
0,093
0.096
0,072
0,095
0.044
0.047
0.091
0.092
0.068
0,069
Pb T (mg/I)
0,043
0.05
ZnT (mg/I)
0.154
0.172
Average values In every perlod.
TABLE 5.7: FINAL EFFLUENTS CSP4/USP4
PERIOD
DATE
1
2
16-29 Jan 90 26Feb-26Mar 90
CONV
FMCT
CONV
FMCT
3
16-30 May 90
CONV
FMCT
4
9-24 Jul 90
CONV
FMCT
5
20Aug-3Sep 90
CONV
FMCT
6
14-31 Jan 91
FMCT
CONV
95
39.1
41.4
30
53.6
82.9
32,6
27,9
47.2
36.6
12,3
VSS (mg/l)
79.3
32.6
34.9
26
45.7
66.4
26.7
22,7
34.3
27.1
B005 T (mg/l)
54.S
27.8
17.6
17
25.2
38.2
12.7
9.5
16.9
10.8
BOOS S (mg/l)
5.5
4.6
2.2
3
3.9
1.7
2.6
2.5
2.5
COD T (mg/l)
233
134
103
112
COD S (mg/1)
74
79.7
SS (mg/1)
TKN T (mg/l)
50.9
29,4
TKNS(mg/l)
41.9
25,3
N-NH3 (mg/1)
43
N-N03 (mg/l)
6.4
TOTAL P (mg/l)
7
18Feb-8Mar91
CONV
FMCT
8.1
12,5
16.3
10,3
7
9.3
11.7
6
7.1
9
10.9
1,3
2.3
2.7
4.3
4.3
132
143
74.9
64,5
93.3
74.1
SI .6
56
68
67.3
62.8
46.4
27,9
28.1
40
30.4
34
36
47.4
46.9
53
15.5
7,6
7.2
11.9
7.9
31.2
30.5
30.6
30.8
70.1
70.2
47.5
9.8
5.3
5.1
7.1
5.9
28,8
28.3
29.2
29
25,6
56.7
61
46.4
5.2
0.5
0.5
6
Z.8
25,7
25.6
23.2
24.7
11.6
0.5
1.8
0.6
23.7
22.8
22.7
16.6
16.7
0,6
0.6
0.3
0.1
9
9
7.7
7.5
10.9
12,2
5.3
5.8
4.5
4.7
2.8
1.3
3.4
2.4
P-P04(mg/I)
7.9
6.7
6.5
7.8
9.7
11.4
4.4
4.5
4,4
4.5
2.3
0.7
2.5
1.8
ALKALINITY (mmol/HCO,")
5.0
3.2
7.02
7.06
5.74
1.28
0.56
0.64
2.26
2.14
4.16
4.16
3.S4
3.70
127.2
129.8
134.4
133,9
91.6
86.4
276.1
297.8
448.1
457.4
192.9
190
432.2
472.4
1.68
1.4
0.45
0.49
0.04S
0,045
OIL t GREASE (mg/l)
SULFIDE (mg/l)
CHLORIDE (mg/l)
PHENOLS (mg/l)
SURFACTANTS (mg/l)
CYANIDE T (mg/l)
Average values In every period.
Ol
M
TABLE 5.8: METALS IN FINAL EFFLUENTS CSP4/USP4
PERIOD
DATE
CaT(mg/l)
2
1
16-20 Jan 90 26Feb-26Mar 90
CONV FMCT CONV FMCT
49,1
47,2
41
41,1
3
16-30 May 90
CONV FMCT
34,4
4
5
9-24 Jul 90 20Aug-3Sep 90
CONV FMCT CONV FMCT
6
14-31 Jan 91
CONV FMCT
7
18Feb-8Mar91
CONV FMCT
36,9
Mg T (mg/I)
6,97
e.55
6.18
6,17
4,68
9,13
Cd T (mg/I)
0,003
0,002
0,002
0.002
0.002
0.002
Cr T (mg/I)
0.016
0.006
0.011
0.007
0,005
0,014
0.019
0,007
0.011
0.011
0,001
0,001
0,003
0.003
Cu T (mg/I)
0,043
0,026
0.015
0,011
0,01
0,024
0,016
0,017
0,015
0,012
0.011
0.019
0,011
0.01
Fe T (mg/I)
9,4
1,6
1.69
1,02
0,72
3,56
0,37
0.67
0.7
Mn T (mg/I)
0,104
0,092
0.062
0,059
0,037
0.069
0.1
0,063
0.073
0,071
0,03«
0,055
0,061
0,06
0.059
NI T (mg/I)
PbT(mg/I)
0,039
0,026
0,019
0,017
0,024
0,031
ZnT(mg/l)
0,149
0,113
0.033
0,042
0,064
0,019
1.5
1.56
3.56
2,22
0.52
0,064
0,06
0,036
0,031
0.063
Avenge values In every perlod.
Ol
CO
TABLE 5.9: DIURNAL VARIATIONS CONVENTIONAL SYSTEM
DATE: 12-Mar-91 (10:00h a.m.) to 13-Mar-91 (8:00h a.m.). Dry weather conditions.
HOUR
Primary clarifier effluent
mg/l
mg/l
mg/l
COD-T COD-S TKN-T
mg/l
N-NH3
Final effluent
mg/l
mg/l
COD-T COD-S
mg/l
COD-T
Mixed liquor
mg/l
mg/l
COD-S N-NH3
Recycle sludge
mg/l
COD-T
10
323
151
37
29
59
46
697
69
26
2475
12
292
13S
36
32
61
46
551
63
26
1743
14
319
151
45
3a
49
46
844
61
26
1377
67
29
2036
29
2109
16
403
159
45
36
49
44
756
16
356
151
45
35
49
44
1019
63
20
348
159
43
36
49
44
873
53
28
2109
52
26
2546
27
2914
22
364
162
39
30
56
44
697
24
360
143
31
23
49
44
580
46
2
311
131
29
22
49
37
551
54
28
2109
52
25
1616
4
253
111
23
18
49
26
990
6
222
115
22
17
49
28
756
44
25
1743
6
216
67
20
18
52
32
287
36
25
1616
AVERAGE
314
139
34
27
51
40
716
55
27
2066
MAX
403
162
45
38
61
46
1019
69
29
2914
MIN
216
67
20
17
49
28
267
36
25
1377
NOTE: CSP1 samples were taken from 13 Mar 91 to 14 Mar 91. with heavy rain between 2 am to 6 am (1< Mar 91)
Operating conditions tn the Plant as Pertod 7.
CTI
TABLE 5.10: DIURNAL VARIATIONS FMCT SYSTEM
DAY: 12-Mar-91 (10:00h a.m.) to 13-Mar-91 (8:00h a.m.). Dry weather conditions.
Hour
Primary clarifier effluent
mg/l
mg/l
mg/l
COD-T COD-S TKN-T
10
190
12
364
14
475
16
568
251
mg/l
N-NH3
Final effluent
mg/l
mg/l
COD-T COD-S
Mixed liquor
mg/l
mg/l
COD-T COD-S
27
20
SB
41
177
71
56
56
46
4968
273
62
47
49
32
4733
42
26
79
44
3445
112
3445
mg/l
N-NH3
Recycle sludge
mg/l
COD-T
31
19008
173
36
19740
160
51
17397
113
38
21790
127
IB
745
333
39
26
70
46
5612
169
29
21937
20
606
257
34
22
73
57
4499
95
43
21790
22
407
205
26
19
73
55
4323
B1
30
22B15
24
230
130
20
15
79
53
3503
50
24
20765
11
79
52
3503
40
23
19008
9
79
53
3737
35
23
21056
2
162
96
15
4
135
63
13
6
79
36
6
S
73
53
3503
44
25
20912
e
63
■ 44
10
7
73
53
4323
40
25
19008
AVERAGE
336
164
30
22
70
46
4132
95
31
20436
MAX
745
33
71
56
79
57
5612
160
51
22815
MIN
79
36
6
5
49
32
3445
35
23
17397
.
NOTE: USP1 samples were taken from 13 Mar 91 to 14 Mar 91, with heavy rain between 2 am to 8 am (14 M ar 91)
Operating conditions in the Plant as Period 7.
Ul
TABLE 5.11: ACTIVATED SLUDGE MASS BALANCE (1)
PERIOD
DATE
1
2
16-29 Jan 90 26Feb-26Mar 90
CONV
FMCT
CONV
FMCT
3
16-30 May 90
CONV
FMCT
4
9-24 Jul 90
FMCT
CONV
5
20Aug-3Sep 90
FMCT
CONV
6
14-31 Jan 91
FMCT
CONV
7
18Feb-8Mar91
FMCT
CONV
Blanket level 0 (m)
2,9
0,49
2.93
2,67
3.27
1.63
No detec
1.17
1.63
1.77
1.97
3,10
1.6
3.4
Blanket level 1 (m)
2.3
1,75
2.97
3,7
2.3
1.45
No detec
1.33
2,55
1.97
1.43
2,9
1.9
3.27
Recycle VSS 0 (kg/m')
5.22
9,06
5,71
11.10
3.72
6.70
2,49
4.67
5.62
9.37
7.116
6.664
2.918
6,2
Recycle VSS 1 (kg/m*)
6.61
11,38
2.72
11.02
3.92
8.06
2.42
4.93
12.628
20.924
5.428
11.924
1.264
9.412
MLVSS 0 (kg/m1)
2,59
2,796
2.20
4.27
1.52
4.68
1.20
3.66
2.67
5.40
2.94
2.84
0.63
3.72
MLVSS 1 (kg/m")
3.77
4,819
1.63
5.11
1.55
4.80
1.07
4.30
3.20
S.13
1.65
3.33
0,74
3.86
Sludge volume In settler 0 (m1)
6.71
0,14
6.63
20.5
6.23
5.24
0
1.94
1.9
6.72
3.16
23.36
233
27,15
Sludge volume In settler 1 (m3)
4,43
G.49
6.98
30.92
4.43
3.69
0
2.85
5.36
9.18
1.26
20.87
2.91
25.52
VSS In settled sludge 0 (kg/m ) (1)
3,47
4.55
3.37
6,55
2.2S
5.35
1.63
4.20
3.65
6.72
4,33
4.76
1.93
5.21
VSS In settled sludge 1 (kg/m*) (1)
4.72
7.01
1,99
7.06
2.34
5.69
1.52
4.51
6.34
10.39
2,91
6.19
0.91
5.71
Sludge mass In settler 0 (kg)
23.26
0.64
23,02
134.21
18.54
28.05
0
8,14
6.94
45.16
13,76
111.76
3.8S
141,54
Sludge mass In settler 1 (kg)
20.69
45.47
13.91
216.91
10.37
21.72
0
12,85
34.13
95.41
3,72
129.25
2.66
145.72
Sludge mass In alratlon tank 0 (kg)
46.62
50.22
39.60
76.66
27.36
64.24
21.60
69.5
48.06
97.20
52.92
51.12
14.94
66.96
Sludge mass In alratlon tank 1 (kg)
67.66
66,76
29.34
91,98
27.90
86.40
19.26
77.40
57.60
92.34
29.70
59.94
13,32
69.46
1
(1) VSS In settler sludge - (2 . MLVSS + Recycle VSS)/3
0 - Beginning of period
1 - End ot period
Ol
TABLE 5.12: ACTIVATED SLUDGE MASS BALANCE (2)
PERIOD
DATE
2
1
16-29 Jan 90 26Feb-26Mar 90
FMCT
CONV
CONV
FMCT
14
Removed BODS (kg/day)
Sludge mass 1 A.S. (kg)
4
9-24 Jul 90
CONV
FMCT
5
20Aug-3Sep 90
FMCT
CONV
6
14-31 Jan 91
CONV
FMCT
7
18Feb-BMar91
FMCT
CONV
14
29
29
15
15
16
16
15
15
18
16
19
19
6.79
2.16
a.60
2.06
10.49
4.35
0.70
1.86
4.87
5.34
6.03
2.50
3,93
15.24
14.5
16.3
15.0
15.2
19.9
16.0
3.6
10.1
20.2
26.3
9.1
10.7
6,2
25.4
67.9
86.8
29.3
92,0
27.9
66.4
19.3
77.4
57,6
92,3
29.7
59,9
13,3
69,5
DAYS
Sludge wasted and lost (1)
(kgVSS/day)
3
16-30 May 90
FMCT
CONV
S.S. (kg)
20.9
45.5
13.9
216.9
10.4
21.7
0.0
12.9
34.1
95,4
3.7
129,3
2.7
145.7
Total(kg)
36.6
132.2
43.3
310.9
36.3
108.1
19.3
90.3
91.7
187,6
33,4
189,2
16.0
215.2
46.6
50.2
39.6
76.9
27.4
64.2
21.6
69.5
46,1
97,2
52,9
51.1
14.9
67.0
Sludge mass 0 A.S. (kg)
S.S. (kg)
23.3
0.6
23.0
134,2
18.5
28.1
0.0
8.1
6.9
45,2
13,8
111.8
3.9
141.5
Total(kg)
69.9
50.9
62.6
211.1
45.9
112.3
21.6
77.6
55,0
142.4
66.7
162,9
18.8
208.5
Sludge mass balance (kg) (2)
113.9
111.6
230.1
159.6
149.7
61.1
8.9
42.6
109.6
125.4
75.3
71.3
71.9
296.2
Total removed BODS (kg)
203.1
226.2
435.1
439.4
299.1
269.7
57.4
161,1
303.6
395.2
164.6
192,0
117.8
462,0
0.56
0.49
0.53
0.36
0.50
0.23
0,15
0.26
0.36
0.32
0.46
0,37
0,61
0,61
Observed Yield (kgVSS/kg BOD5) (3)
(1)
Sludge wasted and lost - (Ow.Xa) + (O-Ow).VSSe
(2)
Sludge mass balance - (Sludge mass 1) • (Sludge mass 0) + (Sludge wasted and lost N 8 days)
(3)
A.S.:
S.S.:
0 :
1:
Observed Yield - sludge mass balance / total removed B0D5
Activated sludge
Secondary settler
Beginning of period
End of period
or
TABLE 5.13: SLUDGE QUALITY
PERIOD
DATE
1
2
16-29 Jan 90 26Feb-26Mar 90
FMCT
CONV
FMCT CONV
SVI (ml/g)
Senang Velocity ( m / h )
Blanket level (m)
3
16-30 May 90
CONV
FMCT
4
9-24 Jul 90
CONV
FMCT
5
20Aug-3Sep 90
CONV
FMCT
6
14-31 Jan 91
CONV
FMCT
7
18Feb-8Mar91
CONV
FMCT
104
119
273
140
299
99
51
65
44
41
143
167
426
107
1.32
0.9
0,35
0.06
0.66
0.36
4,3
1.7
3.4
1.8
0.7
0.2
0.7
0.6
2.1
1.4
2.5
3.1
2.9
1.6
No detec
1,3
1.5
1.7
1.8
2.9
1.6
3.3
4
3
4
4
3
2
2
3
3
♦
4
1
1
2
♦
-
4
-
-
Filamentous M i c r o o r g a n i s m s
(Relative abundance)
Nocardia
S. natans
T.1701
H. hydrossls
T.1663
T.0041
1
2
Fungi
Zooglea
+
-
3
-
1
♦
-
2
-
-
+
-
-
1
1
+
-
+
♦
+
+
-
+
-
1
+
-
-
-
-
++
+♦
-
M L S S (mg/l)
3177
4476
2749
6714
1735
6671
1395
4927
4186
7718
3585
5073
887
5527
MLVSS (mg/l)
2642
3630
2194
5091
1420
5009
1097
3708
3138
5606
2346
3087
650
3618
NOTE1
NOTE 2
Relative Abundance of M i c r o o r g a n i s m s (by E ikelboom)
Zooglea++ : very a b u n d a n t
*
-
Sporadic g r o w t h of filamentous microorganisms
1 L o w g r o w t h of filamentous m i c r o o r g a n i s m s
NOTE3
2 M o d e r a t e g r o w t h of filamentous microorganisms
Settling velocity depends on M L S S concentration
3 High g r o w t h of filamentous microorganisms
4 E xcesive g r o w t h of filamentous microorganisms
5
Field o l v i e w f u l lof filamentous microorganisms
CJ1
00
TABLE 5.14: METALS IN PRIMARY SLUDGE
PERIOD
DATE
Ca (mg/kg dry sludge)
CSP7/UPS7
1
31 January 90
CONV
FMCT
2
14 March 90
CONV
FMCT
29033
32597
41609
41339
40444
26666
26480
25489
3
30 May 90
CONV
FMCT
4
5
25 July 90 4 September 90
FMCT
CONV
FMCT CONV
6
1 - 4 Feb 91
CONV
FMCT
7
8 March 91
CONV
FMCT
Mg
1750
2535
3674
3246
5227
4675
4516
1983
Cd
3,2
3.6
4
5.9
1.9
2
5.6
5.3
Cr
127
326
55,6
57,1
27.6
113
133
136
Cu
565
257
179
175
152
244
460
492
Ft
77156
141163
73168
71260
34819
130746
179325
192094
Mn
372
525
371
378
203
282
1162
1245
997
1057
NI
587
154
127
120
90.7
143
Pb
99
168
218
217
159
91,5
160
154
Zn
496
733
663
644
471
539
962
1018
Hg
ND
NO
1.32
0.79
0.67
0.42
0.12
0.25
SS (mg/t)
13180
14660
35906
36876
30552
16000
31044
12052
VSS(mg/l)
9700
9937
15752
5980
9019
22836
22S76
20783
CJI
co
TABLE 5.15: METALS IN ACTIVATED SLUDGE
PERIOD
DATE
Ca (mg/Kg dry sludge)
1
31 January 90
CONV
FMCT
CSP2/USP2
2
14 March 90
CONV
FMCT
3
30 May 90
CONV
FMCT
5
4
25 July 90 4 September 90
CONV
FMCT
CONV
FMCT
6
1 - 4 Feb 91
CONV
FMCT
7
8 March 91
CONV
FMCT
14052
11367
17915
22972
28098
20067
15113
13781
23894
23019
27733
28759
18337
22303
Mg
2213
221B
2932
2948
3549
3559
4220
4064
2962
3302
4489
6291
3906
5100
Cd
2.2
5.5
2.2
4.1
3
5.9
3.9
5.3
3.9
3.9
5.9
4
6,4
8.3
Cr
77.5
83.2
126
679
82.6
142
70.7
74.2
43.4
46.6
35.9
43,9
25.8
38,3
Cu
232
302
219
360
157
204
347
346
182
183
223
219
75.5
170
F«
32197
36180
35940
50823
18338
36576
69971
73852
62796
68376
55466
62706
332S2
35507
Mn
177
175
224
335
139
214
296
244
434
377
295
393
195
268
NI
166
163
165
218
148
190
214
249
168
177
189
173
66
91
Pb
117
125
124
157
160
182
236
228
146
153
143
173
126
146
Zn
549
571
569
874
704
1018
983
682
551
596
63S
663
460
548
Hg
ND
NO
NO
NO
ND
NO
2.1
3,1
0.49
1,31
1.11
1.06
0.68
0,79
SS (mg/t)
4925
6333
3198
7858
1934
6460
1846
3218
5344
8380
2377
5334
958
5456
VSS(mg/l)
4143
5348
2572
5882
1584
4S66
1338
2512
3744
5648
1657
3472
766
3816
O!
O
TABLE 5.16: AERATION PARAMETERS
PERIOD
DATE
2
1
16-29 Jan 90 26Feb-26Mar 90
FMCT
CONV
FMCT CONV
3
16-30 May 90
FMCT
CONV
4
9-24 Jul 90
CONV
FMCT
5
20Aug-3Sep 90
CONV
FMCT
6
14-31 Jan 91
CONV
FMCT
7
18Feb-8Mar 91
CONV
FMCT
12.9
13,2
15,6
16,4
19,3
19.7
23.7
23,7
22.7
22.6
6.4
8.3
8.4
8.2
Specific OUR (motygVSS.h)
19,62
19,56
12,35
9,92
19,35
15,61
13.64
12.35
22,77
19,50
6,38
11.04
22,1
19.11
OUR (mgOa/Lh)
56,72
70.48
26,9
43,66
29.11
79.7
16
53.3
69
109,7
17,42
39,66
19.34
83.84
0.97
2.65
1.6
2,07
1,64
1.56
1,53
2.5
1.4
1.4
1,63
2,65
1.93
2.51
69
93,2
46
55
67
100.6
32
63.5
96.5
118.8
33
37,4
30
63
Temperature (deg C)
D.O. (mgOj/l)
Air Flow (m'/h)
Relation Air Flow C/F
0.74
Energy In Aeration (kw.h)
1393
Relation of Energy In Aeration
CVF
1.23
C/F-
CONV Une Value
FMCI Une Value
OUR - Oxygen Uptake Rate
0,64
1126
765
0,91
045
465
0.58
0.81
0.50
0.67
796
256
0.51
500
768
0,63
0.88
922
301
0.66
0,48
349
301
0.46
660
TABLE 5.17: ENERGY CONSUMPTION
PERIOD
DATE
Energy In Recirculation pumps (kw.h)
2
1
16-29 Jan 90 26Feb-26Mar 90
FMCT
CONV
FMCT
CONV
3
16-30 May 90
CONV
FMCT
76
62
146
129
75
3S3
4
9-24 Jul 90
CONV
FMCT
5
20Aug-3Sep 90
CONV
FMCT
6
14-31 Jan 91
CONV
FMCT
7
18Feb-8Mar91
FMCT
CONV
114
300
66
1S3
77
70
68
142
301
349
301
660
Energy In Blowers (kw.h)
1393
1126
765
S4S
465
799
256
500
768
922
Total Energy (Kw.h)
1469
1190
913
974
540
1151
370
600
854
1075
378
419
369
602
CD (mVh)
2.53
2.54
2.07
2
2.5
2.3
1.51
3.44
5.9
6.2
2.56
3.14
1.76
6.58
N«days
Flow Treated (m1)
Energy Consumption Total (kw.h/m*)
Energy Consumption In areatlon (kw.h/m*)
14
14
29
29
15
15
16
16
15
15
18
18
19
19
650.06
S53.4
1440,72
1392
900
626
579.8
1320.9
2124
2952
1105.92
1356.48
811.66
3000.48
1.73
1,40
0.63
0.70
0.60
1.39
0.64
0.61
0,40
0,36
0.34
0.31
0.4S
0.27
0,31
0.27
0.25
0,37
0.22
1.64
1.32
0.53
0.60
0.51
0.96
0.44
0.36
0,36
B005 Removed (kg)
203.1
226,2
435.1
439.4
299.1
269,7
57.4
161.1
303,6
395,2
164.6
192.0
117.6
462.0
B005 Removed (kg/day)
14,51
16.3
15,0
15.15
19.93
17,96
3.58
10.06
20,23
26,34
9.14
10.66
6.20
2S.36
7.23
5,22
2,10
2.22
1.61
4.27
6.45
4.97
2.B1
2.72
2.30
2.16
3.13
1.66
2.96
4.45
3.10
2.S3
2.33
1.63
1.61
2JJ
1.37
Energy Consumption Total
(kw.h/kgBCO)
Energy Consumption (kw.h alratlon/kg BOO)
Air Consumption (m'/day)
m* alr/kg BOO removed
6.66
4,94
1.76
1.92
1.5S
1.656
2.237
1.104
1.320
1.608
2.414
766
1.524
2.316
2.651
792
896
720
1.512
114.13
137.24
73.6
67.13
60.66
134.26
214.5
151.49
114.46
108.24
86.65
84.24
116,13
59.62
Note: In period 1 atr diffusera were clogged and were replaced for new ones In period 2. So that the Energy consumption In blowers In period 1 is much higher than In other periods.
TABLE 5.18 : SLUDGE AGE CALCULATION
PERIOD
DATE
2
1
16-29 Jan 90 26Feb-26Mar 90
CONV
FMCT
CONV
FMCT
Temperatur« (*C]
3
16-30 May 90
CONV
FMCT
4
5
9-24 Jul 90 20Aug-30Sep 90
CONV
FMCT
FMCT
CONV
6
14-31 Jan 91
FMCT
CONV
7
18Feb-8Mar 91
FMCT
CONV
12.9
13.2
15,6
16.4
19.3
19.7
23,7
23.7
22.7
22.6
6,4
6.3
6,4
6.2
14
14
29
29
15
15
16
16
15
15
16
1B
19
19
Fexcese (kg VSS/day)
6.79
2.16
6.60
2.06
10.49
4.35
0.70
1,66
4.67
5,34
6,03
2.50
3.93
15,24
Mxl (kg)
60.8
132,2
43.3
310.9
36.3
106.1
19,3
90,3
91.7
167.6
33,4
169,2
16.0
215.2
MxO(kg)
69.9
50.9
62.6
211.1
45.9
112.3
21.6
77,6
55,0
142,4
66.7
162.9
16.6
206.5
1.3
9.6
-0.7
3.4
-0,5
-0.3
-0.1
0,6
2,4
3,0
-1.9
1.5
-0.1
0.4
Ntdays
(MX1-MMO)/N (kg/day)
79.4
91,6
53.0
261.0
42,1
110.2
20.5
64,0
73.4
165,1
50.1
176,1
17,4
211.9
[(Mx1-MxO)/N]»Fexce>s (kg/day)
6.1
6.0
7.9
5.5
10,0
4.1
0.6
2,7
7,3
6,4
4.2
4,0
3,6
15,6
Total aludge age (days) (1)
9.6
11.5
6.7
47.4
4.2
27.1
36.6
31.4
10.0
19.7
12.0
44.4
4,6
13.6
47.6
65.3
39.4
91.6
25.6
90,2
19.6
66.7
56.5
100,9
42.2
5S.6
11.7
65.1
5.6
6.2
5.0
16.7
2.6
22,1
35.5
25.0
7.7
12,1
10,1
14.0
3.1
4.2
43.0
25.6
58.7
61 J)
46.4
5.2
0.5
O.S
6.0
2,6
25.7
25.6
23.2
24.7
(MK1«MXO)/2 (kg)
Va.Xa (kg)
Aerobic sludge age (day«) (2)
N-NH3 In effluent (mg/l)
(1)
Total sludge age (days) -
(Mx1+Mx01/2
[(Mx1-Mxü)/NJ+(-excess
(2)
Aerobic sludge age (days) -
Vo.Xfl
L(Mx1-MxÚ)7NJ+t-excess
Fexcess -
Sludge wasted and lost (kgVSS/d)
Mx1 -
Total sludge mass (kg) end of period
MxO-
Total sludge mass (kg) beginning of period
((Mx .•Mx0)/N]+Fexcess -
Sludge acumutated En the system (kg/day) + sludge wasted and lost (kg/day)
VauXa -
Average sludge mass In alratlon tank (kg)
O)
-646 MODELLING
6.1 Introduction
To verify and analyze the obtained experimental data against the known theory, a
computer program CAB (Consorcio de Aguas, Bilbao) was developed. The program
includes current theory for activated sludge reactors and clarifiers, and is therefore a
valuable tool which can be used in understanding and interpreting measured data.
This chapter shortly describes the implemented mathematical models, the model set
up of the plant and the results obtained from calculations with the program.
6.2 Concepts and models
The process model used in CAB is based on the IAWPRC Activated Sludge Model
No 1. (Henze et al, 1987), and for the secondary clarifiers on the flux theory adapted
for modelling with the activated sludge models (Dupont, 1991).
6.2.1 Activated sludge model
The model for activated sludge is presented in figure 6.1. Explanations of the
components and constants are found in the symbol list at the end of the chapter. The
model is a slightly expanded version of the original Activated Sludge Model No. 1
(Henze et al, 1987).
To prevent numerical problems for components in the model which have a negative
stoichiometric constant, a few new terms are added to some of the processes. Finally,
three new components (Particulate precipitated compounds Xpg, Particulate
orthophosphate XPO, soluble phosphate SP0) and three new processes (process 10,11
and 17) are added to deal with simultaneous precipitation.
A general description of the included components and processes can be found in
numerous papers (Henze et al, 1989; Gujer, 1991).
Component -
Process I
12
*BH
Xpo
XBA
13
14
17
Process rates
ML"J-Tn
Spo
1 Aerobic growth
Y„-1
of heterotrophic
°NH
IV
°AIK
^ H ^ S R K Q H ^ O ^NH^NH ^AH^AIK
2 Anoxic growth
-1*Y H
of heterotrophic
1-Yu
f,
S
*OH
MH-
2,86-YH
KSH^SR
KOH'SO
K
N
NOH' , S NO K N H ^ N H
KAH'SAU
3 decay of
heterotrophic
1-f.
U-l. -
"H-*BH
4 Aerobic growth
of autotrophic
^"YT
->nb
1
YA-4.5
KA-
So
KNA^NH
KOA*SQ
KAA^ALK
•XBA
5 Decay of
autotrophic
1-f.
B
A-XBA
6 Hydrolysis of
KHX-
Particulate
Xs-
(1Æ2H)-XBH
7 Hydrolysis of slowly
degradable
^HS'SŞŞ'XBH
8 Hydrolysis of
particulate organic
•nu
,e.
9 Ammonification.
^HND-^— 'fO)
14
10 Iron oxidation.
-2
3ï
11 Precipitation.
2_
31
J6
T
Ket' S 0 -
-• S n
KAO^ALK
*ME ^PO *FE
12 Resolubilisation.
-2
31
Figure 6.1 Activated sludge model matrix.
Kpo'
05
oí
-666.2.2 Secondary clarifier model
The model for the secondary clarifier is based on the zone settling theory for sedimentation in clarifiers described among others by Vesilind, 1979, and Ekama et al, 1984, and
adopted for use with activated sludge models by Dupont, 1991.
The conceptual idea by the implemented
secondary clarifier is shown in figure 6.2.
The clarifier is regarded as a flat bottom
cylindrical tank with a given height and a
given area, in which an inlet is placed in
a given depth, from which there is an
upward flow and a downward flow. These
flows together with the gravity settling of
the particles gives the flux expressions for
the upper an lower part of the clarifier.
Total flux expression :
GT = Gt + GF = V¿Xs * VpXs (6.1)
: Total flux
Gravity flux
: Flow flux
Vg : Settling Velocity
Xss: Sludge concentration.
VF : Flow velocity
Figure 62 Conceptual model for clarifier.
Expression for flow velocity:
V =
^F =
—
A
ÖR + ßp
for h > h .„,
(6.2)
for h < h inlet
A : Area of clarifier
h : Height of clarifier
Q E : Effluent flow
QR : Return sludge flow
Qp : Waste sludge flow
67
Expression for settling velocity:
(63)
-h-Xs
Vt = V0- e
V0 : Max settling velocity due to gravity
k : Sludge quality constant
Inserting expression 6.2 and 6.3 in the total flux expression 6.1 the following expressions
for flux in the upper and lower part of the clarifier are obtained:
Gj. =
~Ã J
{ °
■Xs
for h > h jnJet
2 p ' • J£¡
GT =
for h < h
(6.4)
(6.5)
To be able to model the sludge which does not settle in the clarifier, the following
empirical model is used for suspended solids in the inlet to the clarifier.
'NO,
-^NS
=
-^lnit
+
-*^N03
(6.6)
^N03 + ^N03
Y
NS
xs,Init
xs,N03
^N03
: Non settled suspended solids in inlet to clarifier which will not settle
: Floating particles in the inlet to the clarifier.
: Max concentration of suspended solids due to nitrate in the inlet to the
clarifier, which will not settle.
: Monod constant for nitrate.
: Concentration of nitrate in the inlet to the clarifier.
Applying model 6.4, 6.5 and 6.6 to mass balances over tiny elements of layers in the
clarifier, the concentration profile in the clarifier can continuously be calculated over
time by integration.
-68-
6.3 CAB description
CAB (Consorcio de Aguas, Bilbao) is a dynamic simulation program developed for this
project. The purpose of the program has been to develop a program which could be used
as an analyzing tool and which could support the work of verifying and analyzing the
experimental data. In the development of the program special attention is paid to the
clarifier part, because the differences in clarifier design is a key factor in the difference
of the two pilot plant lines.
One of the goals for the program was that it should be possible to run the program on
any PC type computer. This has been achieved, but reasonable minimum hardware
requirements would be PC with a 286 processor, a mathematical co-processor and a
graphic screen.
Plant
Operatio
Constants
-CAB Version 1.0Presentation System utilities
Exit
Plant
Table of plants
Flow scheme
Ctrl-T
Dimensions
Dimensions
Volume of Activ, sludge 1
Surface aeration (Kla) for Activ, sludge 1
1 8 0 ra 3
1 0 1/d
Surface area of Final sed. 1
Height of Final sed. 1
Position of inlet in Final sed. 1 •
1 2 5 m3
4 4 m
1 3 m
Plant: USP
Const:
Input tank volumes
<F1> Help
<F10> Save
Influent:
RAH Max :
213016 Avail:
213008 bytes
Figure 63 Example on user interface from CAB.
The program is driven by pull down menus (Figure 6.3), from where the different tasks
can be operated. This includes :
- Possibilities for setting up the configuration and dimensions of the plant.
- Possibilities for operating the designed plant with different controls and operating
strategies.
- Possibility to simulate dynamic load conditions.
- Possibility for calibrating the model by adjusting model constants.
- Graphic and table output of calculation results
69
The program and manual for the program can be found in annex 6.
6.4 Model Plant
For model purposes a simplified flow sheet of the plant was set up (Figure 6.4). Due
to the fact that both lines have the same flow sheet (but different dimensions), only the
flow sheet for one pilot plant line is drawn. The actual plants includes a primary clarifier,
but this is not included here because CAB do not include a model for the primary
clarifier.
The figures (SPx) on the flow sheet
are the measuring points, where
SP2
samples where taken.
The effluent pipe (SP6) from the
bottom of the clarifier in the flow
sheet is only used for sample-taking
and not for control of sludge mass
and sludge age. The actual sludge
SPI .
3
V
.i—iM
AS
/i
«* SlrD
wasting is handled by the pipe from Figure 6.4 Pilot plant flow sheet used for
the activated sludge reactor (SP2). modelling
In table 6.1 the physical dimensions of the pilot plant used for modelling is listed. In the
table is given an actual inlet height, and a used inlet height. A lower height is used in
the modelling, as it is not possible to model a sludge blanket height which is below the
actual inlet height with the present one dimensional flux model. The only consequence
of this is that the retention time for both water and biomass in the clarifier might be
longer, giving a larger delay and damping in the clarifier than expected.
70CONV
FMCr
3
Volume of Activated sludge reactor
18 m
18 m3
Area of secondary clarifier
3.8 m2
12.5 m2
4m
4.5 m
Actual
2m
2.4 m
Used
1.2 m
1.3 m
Height of secondary clarifier
Depth of inlet in secondary clarifier
Table 6.1 Dimension of the CONV and the FMCT line of the pilot plant.
It is further seen that the volume of the clarifier at the FMCT line is much greater than
the volume of the clarifier in the conventional line. This is the key difference between
the two lines in the plant.
6.5 Input data handling
The data which are obtained from the pilot plant are very comprehensive and cover a
long period of intensive measurements of many parameters. From these data 4 periods
were selected for further modelling, covering the last 4 periods of intensive measurement.
The raw data as they are used for modelling are listed in Annexes 7.1 to 7.4. Hatched
fields in the tables are fields that contain estimated data.
Three reasons make it necessary to check the data and make some corrections and
calculations before they can be input to the model :
- The model is not able to handle data in the inlet which is inconsistent regarding to
mass balances. The influent measurements must be checked for mass balance
inconsistency, and eventually new values must be extrapolated if inconsistency is found.
- To avoid missing data it is necessary to estimate values in cases where no measuring
was conducted.
- As the model internally deals with model components, all of which it are not possible
to be measured at present, it is necessary to estimate values for these components by
conversion of the measured influent data. This conversion must be conducted both for
inlet data, and for output data, converting model data back to measurable data.
-71 In the two first cases above the estimation of data is best done before the data are entered
into the program. In the last case the conversion of the measured data is done entirely by the
program. The user can control this conversion by means of conversion constants given to the
program (Table 6.2).
CONV
FMCT
CONV
FMCT
COEV!oluhl./CODIotlll
0.42S
0383
5%H/^particulate
0.99S
0.995
Bor^olubl./BODrot.i.
0.422
0.410
0.005
0.005
BOD/BOPrnfinit.
0.6
0.6
'%A/B0I}?«rticiiLt.
}%/BODpartlculat.
0.900
0.900
BOD!n£lnlt./COD
0.729
0.696
%s/cor% o l u b l .
0.5
OS
Kj-hfeojjifcx./Kj-Nrotal
0.835
0312
%R/ C O E %olubl.
OS
OS
NIVN/KJ-NÎO1U1J1.
0.882
0384
PCVP/Frot«!
0.637
0.642
Constant
Constant
Table 62 Conversion constants used for the inlet.
The conversion constants are based on mean values for all the measured data of the 4 periods. The
conversion constants are regarded as being identical in the 4 periods.
The variations patterns for total COD and total Kjeldhal-N of the influent from the 4 periods are
shown in figure 6.5 to 6.8. There is no significant difference in the influent variation of the two lines.
Figure 6.5 Influent patterns of total COD
Figure 6.6 Influent patterns of total COD
and total Kjeldhal-N from period 4
and total Kjeldhal-N from period 5
72
Figure 6.7 Influent patterns of total COD
Figure 6.8 Influent patterns of total COD
and total Kjeldhal-N from period 6
and total Kjeldhal-N from period 7
6.6 Operation conditions used for modelling
CONV6
FMCT6
CONV7
FMCT7
Units
CONV4
FMCT4
CONV5
FMCT5
Oxygen
13
23
13
1.8S
1.7
2.75
13
23
mg/l
Inlet flow
13
3.4
6
&2
VAR1'
VAR1'
VAR1'
VAR1'
m 3 /h
Return flow
3
9
13
VAR3)
50%
50%
50%
50%
ni/h
Waste flow
0
0
0
0
VAR2)
VARZ)
VAR2'
VAR2'
m 3 /h
Temperature
20
20
22.8
218
113
8.6
8.2
8.2
oC
Parameter
Notes :
1) The inlet flow is variable, but controlled to keep the F/M ratio constant
2) The waste flow is variable, controlled by the sludge blanket
3) During period 5 the return sludge flow in the FMCT line decreased from 8.2 to 2 3 m /h
Table 6.3 Operation conditions for modelling
Table 6.3 shows the operation conditions as they are used under the simulation, and in most cases
these are the same operation conditions as used in the pilot plants.
-73-
6.7 Modelling and analyzing
In this work, analyzing the experimental data is conducted as calibrations on each of the 4 periods
and in the two plants. In this way it is possible to find out whether there is any deviation from
expected behaviour of the plant. This could either be of the plant in general or for a single period.
If there is found any deviations then the program is valuable tool to use, helping to explain the cause
of the deviation.
6.7.1 Notes on modelling
The retention time and damping of the effluent concentrations from the clarifier is greater than
expected. This due to the fact that the actual used inlet by the modelling is lower than the physical
inlet depth of the clarifier. This is the only way to model sludge blanket dynamics with a one
dimensional clarifier model, when the measured sludge blanket is below the physical inlet of the
clarifier (see operating conditions table 6.3).
The modelling of period 4 for the conventional line is a special case of the case above and gives
some problems in form of a very low or non existing sludge blanket. To model the concentration,
the sludge age and the height of the sludge blanket in this period, it was necessary to model the
clarifier with a inlet in the lowest possible level (in this case 0.2 m). This gives as explained above
a greater retention time in the clarifier.
During the calibrations it was assumed that the plant during the intensive periods was not in a
transition period. This gives the advantage that the same period can be run over and over. This is
very difficult to handle in period 4 and 5, because of the very low sludge wasting, which made the
sludge mass in the system slowly, but continuously increasing. This in turn reflects that the system
might not be totally in balance.
-74-
BODinfinity/BOD
CONV4
FMCT4
C0NV5
FMCT5
CONV 6
FMCT6
CONV 7
FMCT7
1.667
1.667
1.667
1.667
1.667
1.667
1.667
1.667
Uniu
0.71
0.77
0.75
0.64
0.76
0.7
0.7
0.71
jBOO/sCOO
0.7
0.8
0.7$
SBOO/gCOO
eBOO/sBOD
BOD/CODtotal
Effluent
0.85
0.6S
0.7S
0.64
OS
Effluent
0.6
0.6
0.7
0.61
0.7
0.64
0.66
0.69
SSS/tCOO
Clarifier
0-5
0.6
0.7
0.61
0.7
0.6
0.6
OS
sss/scoo
Qarìfìcr
SS/CODrot.1
Table 6.4 Conversion constants used for effluent and secondary clarifier
In table 6.4 are listed conversion constants for the effluent and for the secondary clarifier .
The values for the effluent are mean values calculated form the measured data for each period.
The values for the secondary clarifier were found by calibration.
The conversion constants are mainly used for converting the measured influent components
to the components used by the model, and for converting the model components to measurable
components which can be compared with the respective measured values. The secondary
clarifier makes an very important exception to this. In the secondary clarifier, the three
constants which convert particulate model components of COD, particulate iron, and
precipitated phosphorus compounds to SS are used to calculate the sedimentation rate of the
particulate components. When calibrating a model it is very important to be aware of this, as
it can change the mass of suspended solids in the clarifier and thereby have an impact on the
sludge age and sludge blanket height
During the modelling, one of the objectives has been to calibrate the constants and the
operation so that the calculated sludge blanket and sludge age are matching the sludge blanket
height and sludge age obtained during the experiments. In this way the sludge blanket and the
sludge age become operating parameters.
6.7.2 Some results from the modelling of the pilot plant
In this paragraph are described some of the key results from the modelling, and a few
representative curves are shown with comments.
75-
Table 6.5 shows mean values of some key results from the calibration. As it can be seen the
modelling results are comparable with the results obtained from the measured data.
CONV6
FMCT6
CONV7
FMCT7
1.72
1.8
1.7
1.8
2.9
1.8
33
m
2.9
2.0
33
m
10
19.7
12
44.4
4.6
13.6
days
36
10
25
14
50
15
9
days
35.5
25
34
24
7.7
12.1
10.1
14
3.1
42
days
8
13
10
14
3
3
days
Measured
16.0
Calculated
21
533
69.0
109.7
17.4
39.7
193
63.6
46
75
83
18.8
21
125
355
CONV4
FMCT4
CONV5
FMCT5
Measured
-
1.4
1.4
Calculated
0.2
1.4
1.4
Measured
36.8
31.4
Calculated
35
Measured
Calculated
Parameter
Uniu
Sludge blanket
Total sludge age
Aerobic sludge age
OUR
Table 6.5 Key results from modelling. Mean values.
jtf
Figure 6.9 COD total from Conventional
Figure 6.10 COD soluble from Conven-
line, period 5.
tional line, period 5
Figure 6.9 and 6.10 show the modelling results from the conventional line, period 5, of total
COD and soluble COD. The modelling results for COD correlate with the measured values
quite well. For soluble COD the calculated values tends to give higher values than the
measured ones. This is probably caused by soluble inert COD from the influent. The soluble
inert COD in the influent tends to be estimated to high with the currently used methods
(Soluble inert COD = soluble COD - soluble BODinfinite).
76-
Figure 6.11 and 6.12 shows BOD total and BOD soluble from the FMCT line in period 7.
The general trend for these results is that the calculated mean concentration for total BOD
match the measured values very well, but the dynamics is missing in the calculations. The
calculation generally estimates the Soluble BOD concentration to high. This could possibly be
corrected by lowering the Monod constant for soluble substrate in the growth process for
heterotrophic bacteria (See paragraph 6.7.3).
Figure 6.11 BOD total from FMCT line,
Figure 6.12 BOD soluble from FMCT
period 7
line, period 7
±=
il 111 9
Figure 6.13 SS concentration in CONV
Figure 6.14 Alkalinity from Conventional
line, Period 7
line, period 6
Figure 6.13 shows the concentration of suspended solids in period 7 of the Conventional line.
In the shown figure the suspended solid concentration matches the measured values very well,
but in general the calculated curves are less dynamic than the measured values. Figure 6.14
shows the alkalinity from Conventional line period 6. Except for period 4 the calculated
alkalinity concentration correlates with the measured values very well.
-77-
Figure 6.15 and 6.16 shows total Kjeldhal-N and Ammonia/Nitrate curves from Conventional
line period 4. By the modelling total Kjeldhal-N is often predicted to be lower than the
measured concentration. For ammonia and nitrate the modelling gives results which matches
the measured values (See comments on the hydrolysis constants KHX and KHND in the next
paragraph).
Figure 6.15 Total Kjeldhal-N from Con-
Figure 6.16 Ammonia and Nitrate from
ventional line, period 4
Conventional line, period 4
6.7.3 Calibration of constants in the model
By the calibration the main points for focus is one hand the constants related to the secondary clarifier controlling the effluent quality, the concentrations of suspended solids in the
process tanks, the sludge age, and the sludge blanket height. On the other hand the constants
related to the activated sludge processes controlling the concentration of COD and the nitrogen components in the process tanks.
-78
Default
CONV4
FMCT4
CONV5
FMCT5
CONV6
FMCT6
CONV7
FMCT7
Unit
(.1
0.06
0.005
0.005
0.005
0.005
0.005
0.005
0.005
0.005
gN/gCOO
I%H
20
IS
25
25
2-5
IS
Z5
25
IS
gCOO/m 3
•%X
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
m3/gCOOAl
•%HD
0.25
025
0.25
0.25
0.25
0.25
0.25
0.25
0.25
T«03
0.098
0.103
0.103
0.103
0.103
0.103
0.103
0.103
0.103
KiiA
1
1.0
0.25
1.0
0.25
1.0
0.25
1.0
0.25
gN/m3
m/d
Constant
V0
137
130
130
130
130
160
150
170
150
k
037
0.75
0.65
02
OJ
0.8
0.75
11
0.6
m 3 AQ
SSlnit
5
S
S
10
10
5
6
5
6
g SS/m 3
S%03
25
10
10
20
20
20
20
20
20
gN/m3
Table 6.6 Constants found by calibration of the Pilot Plant
In table 6.6 are listed the default constants of the model together with constants which were
changed during the calibration. The default values of other constants of the model can be
found in the symbol list. Only a few of the constants in the model were changed. Most of the
changes are small and kept within normal limits of variation. In the following is a short description of the changes and there implications.
Comments to constants regarding activated sludge processes.
fM : Fraction of nitrogen in inert material. This constant is changed to a very low value, to
meet the requirements of the nitrogen mass balance of the influent wastewater. If this value
was greater there would be a much greater need for estimation of some of the measured values
in the influent.
KsH : Monod constant for substrate of heterotrophic bacteria. As it was not possible with the
default constant to match the measured values of soluble BOD, this constant is changed to a
lower value. As seen in figure 6.7 this value might even be lower than the calibration value
of 2.5 g/m3. Experience has shown that it is often necessary to decrease this Monod constant
to get the desired results. Therefore it can not be regarded as being a special feature of the
Bilbao waste water.
-79-
Krøj and KHND : Hydrolysis rate for COD, and hydrolysis rate for nitrogen. These constants
are estimated to be lower than the default values. With the default values of this constants the
particulate Kjeldahl nitrogen in some of the periods is calculated to be lower then the
measured values. The low values estimated by the calibration compensate somewhat for this
(Figure 6.8) as it increases the amount of particulate degradable COD and the nitrogen bound
in organic substrate. As the theoretical value of these constants is nearly unknown, it can not
be concluded from this that these constants are a consequence of unusual wastewater in Bilbao.
T N03 : Temperature coefficient for nitrification. The value are slightly changed, compared to
the default value, to obtain a greater dependency of the nitrification on temperature. This is
done to achieve a lower nitrification at low temperatures. By the modelling this accounts for
all the differences in the nitrification rates in the four periods. But one must be aware that the
measurements show that there is a rather low alkalinity in the wastewater, and this could give
a reason for reduced nitrification under certain circumstances. This situation could not be
observed by the modelling as there is no inhibition of nitrification by low pH included in the
model.
Comments on constants regarding secondary clarifier performance.
V„, k One of the more interesting changes witch is made affects the constants for calculating
the sludge settling velocity (The Maximum settling velocity V0 and the sludge characteristic
constant k). These constants reflects the settling properties of the sludge. In general it is not
possible to estimate a general value for these constants, because they are very dependent on
the actual settling performance of the sludge which in turn is dependent on temperature,
reactor configuration, bacterial composition, influent composition etc. The constants Vo and
k is very important for the calibration of the sludge blanket height and the sludge age.
From figure 7.7 it is seen that the maximum settling rate can be determinate from the
expression:
ln(V0) = 2 *
V0 = 170 m/d
Comparing this value to the calculated values in table 6.7 it is seen that the calculated values
in general are lower. However comparing the dynamics of the calculated sludge blanket with
the measured sludge blanket it was observed that the dynamics of the sludge blanket height
of the modelling was more dynamic than the measured value. Taking this in account the values
from the calibration is not contradictory to values above.
-80
The k value reflect the sludge volume in the clarifier, and it is possible to compare the k
value with the measured sludge volume index. Figure 6.17 shows the estimated k value as
function of the measured SVI values of table 13. As it can be observed this correlate reasonably good.
As the k value reflects settling properties of the
clarifier it can be deduced that at high temperatures as in period 4, and especially in period 5,
there was a very good settling. I contrary to this,
the settling in period 6 and 7 at the low temperature was very poor. This is especially true for the
conventional line in period 7.
Figure 6.17 Estimated k values as function of measured SVI
6.8 Conclusion
The program has shown to be a valuable tool for
analyzing data. The program can tell whether there is any reason for concern, regarding the
composition of a certain waste water, and it can give some indication of the consequences on
the effluent quality and the operation of the plant with this waste water. Further it can be
helpful in explaining measured results.
From the work with the program it can be
concluded that the calibration of the model can be conducted without serious change of
constant values. This indicates that there is nothing which indicates that the investigated waste
water of Bilbao has a special composition. One must keep in mind that this conclusion is valid
inside the limitations of the model. The measurements (See chapter 7) has revealed that there
might be problems with nitrification because of low alkalinity.
However the calibration of the constants regarding the secondary settler, indicates that a
configuration of the waste water treatment plant similar to the pilot plant could favour bulking
tendencies in the plant, especially at low temperatures.
-81
6.9 List of symbols
Components in activated sludge model CUnit g/m3)
V
BH
Xs
X,
x,ND
M>0
°NH
SND
^NO
Spo
^ALK
So
SFE
S,
Heterotrophic bacteria
Autotrophic bacteria
Particulate degradable organic COD
Particulate inert organic COD
Particulate precipitated iron
Particulate degradable organic nitrogen
Particulate orthophosphate
Soluble slowly degradable substrate COD
Soluble easily degradable substrate COD
Ammonium
Soluble degradable organic nitrogen
Nitrate
Orthophosphate
Alkalinity
Oxygen
Soluble iron
Soluble inert organic COD
g COD/m3
g COD/m3
g COD/m3
g COD/m3
g Fe 3+ /m 3
gN/m 3
g FeP0 4 /m 3
g COD/m3
g COD/m3
gN/m 3
gN/m 3
gN/m 3
gP/m 3
g HCOVm3
g COD/m3
g Fe 2+ /m 3
g COD/m3
Stoichiometric constants in activated sludge model
default value
Constant
0.67
YH
: Heterotrophic yield
Autotrophic yield
0.24
Nitrogen in bacteria
0.086
Nitrogen in inert substrate
0.06
Fraction of endogenous day
0.08
Kinetic constants of heterotrophs in activated sludge model
Constant
default value
: Heterotrophic growth rate
6
: Heterotrophic decay rate
0.62
BH
: Monod constant for substrate
20
KSH
: Monod constant for oxygen
0.20
KOH
: Monod constant for ammonium 0.01
KVNH
N
: Monod constant for alkalinity
0.10
K,NOH : Monod constant for nitrate
0.50
: Fraction of denitrifiers
0.80
Unit
g COD/g COD
g COD/g COD
g N/g COD
g N/g COD
g COD/g COD
Unit
d"1
d"1
g COD/m3
g COD/m3
gN/m 3
g HCOVm3
gN/m 3
-82-
Kinetic constants of autotrophs in activated sludge model
Constant
default value
HA
: Autotrophic growth rate
0.8
BA
: Autotrophic decay rate
0.15
K^
: Monod constant for nitrate
1.0
KQA
: Monod constant for oxygen
0.40
KAA
: Monod constant for alkalinity
0.30
Kinetic constants of hydrolysis in activated sludge model
Constant
default value
KHX
: Particulate substrate hydrolysis 0.005
KHS
: Soluble substrate hydrolysis
4.00
K HND : Ammonification
1.00
r\ h
: Correction for lower anoxic
hydrolysis
0.40
Kinetic constants for simultaneous precipitation
Constant
default value
KFe
: Iron oxidation rate
50
KMe
: Precipitation rate
1.0
Kp 0
: Resolubilisation rate
0.40
Secondary clarifier
Constant
default value
GT
: Total flux
Gg
: Gravity flux
GF
: Flow
flux
Vg
: Setüing Velocity
XJS
: Sludge concentration
VF
: Flow velocity
A
: Area of clarifier
h
: Height of clarifier
QE
: Effluent
flow
QR
: Return sludge
flow
Qp
: Waste sludge
flow
V0
: Max settling velocity
137
k
: Sludge characteristic constant
037
X NS
: Non settled suspended solids
XS Ini , : Floating particles in sludge
10
XS N 0 3 : Max non settled SS due to N 0 3
KN03
: Monod constant for SS
20
S
:
NO3
Nitrate concentration
Unit
d"1
d'1
g N/m 3
g COD/m 3
g HCOVm 3
Unit
m 3 /(g COD d)
m 3 /(g COD d)
Unit
/ ( g Fe 2+ d)
m 3 /(g Fe 3+ d)
d'1
m3
Unit
g/m 2 /d
g/m 2 /d
g/m 2 /d
g/m 2 /d
g SS/m 3
m/d
m2
m
m 3 /d
m 3 /d
m 3 /d
m/d
m 3 /kg
g SS/m
g SS/m 3
g SS/m 3
g N0 3 /m 3
gN0 3 /m 3
-837.DISCUSSI0N OF RESULTS
In this chapter the results presented in chapter 5 and 6 will be discussed. The
discussion will focus on two aspects:
- the general treatability of the wastewater of Bilbao in a biological activated
sludge process
- comparison between the two process lines investigated (CONV and FMCT)
7.1.
Primary settling
The results from the two process lines are similar. All data from the intensive periods
4,5,6 and 7 are given in Figure 7.1 and 7.2. Figure 7.1 shows the suspended solids in
the effluent as a function of suspended solids in the influent. For the typical influent
concentrations, the removal efficiency is approximately 50 per cent, which is in the
low end of the normal expected range of 40-70 percent (Abwassertechnologie, 1988).
Figure 7.2 shows the COD reduction over the primary clarifier which amounts to 2535 per cent. The removal of inorganic suspended solids is slightly higher than that of
VSS which means that the ratio CODT^/SS increases slightly over the primary settler
as seen in table 7.1. The ratio CODT^/VSS is essentially unchanged over the primary
settler, indicating that the average composition of the suspended organic matter is
not significantly affected by the primary settling. The slight increase is soluble COD
is caused by hydrolysis of suspended solids during settling. In this case approximately
3 per cent of the particulate COD has been solubilized during primary settling.
Fiq.7.1.
Periods
,
,
SSe v s SSi i n P r i m a r y s e t t l e r
4 , 5 , 6 , 7 . L i n e s CONV a n d FMCT.
. , . ,
. . . .
■ ,
. . . .
, , , ,
. . . . I . . . ,
i
i
i
i
1
1
1
1
250
D
D
200
a
en
E
\_^
+>
C
dl
D
6
DD
150 ° D
D
D
• D fr
C
° /'S
D
D
D
100
D
a
D
B
D
D
n
CP
D
D
nD
9D
.p
•
■ ■ ° Ba
D
j
?
D
D
00
p
° n
mi
D
D
DD
;
a
?
d?
D D
D
■
_ -'
Do
D
Eb
D
D
b
D
.
D
D
:
^ b
D •
P,
a
D
D
m
.
D.%..:.... °
D
UUISl
D
D
□
m
D
D
D
'
a.
D
°
DD
D
50 l i l i
50
|
1 l
100
1 1
l i l i
150
1 1 1 1
200
i i i i 1 i i i i
250
SSinfluent
300
l
350
(mg/l).
l
l
l
I l l 1
400
450
500
F i q . 7 . 2 . CO De vs CO Di in Primary settler
Periods 4,5,6,7. Lines CO NV and FMCT.
I ! I I I I
600
500
tflU
O)
5
400
+>
c
m
□
D
U-
D
d- Q
300
ai
Q
o
00
ai
D
D
DD
q *
%a
fia
¡O
□
PB?
200
100 I
1 I
100
I
I I
I
200
I
I
1 I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I
300
400
500
600
700
CODinfluent (mg/l).
800
900
1000
86
Table 7.1 Primary Settling. Period 4,5,6 and 7, average values.
Parameter
SS
VSS
NVSS
COD
T
Influent
Effl. primary
% reduction
COD
s
CODT.s
CODTJ
SS
CODT.s/
VSS
265
177
88
. 475
128
347
1.31
1.96
134
97
37
336
138
198
1.48
2.04
49
45
58
29
-8
43
-
-
Results from full scale operation of primary clarifiers, show that the removal
efficiency is somewhat higher than in the pilot plant.
7.2.
Activated sludge process
Various aspects of the process will be discussed, including nitrification, sludge
quality, effluent quality, sludge yield and energy consumption
7.2.1 Nitrification
The pilot plant has been operated to get nitrification at high operating temperatures. This has been achieved as shown at Figure 7.3 and 7.4. To obtain nitrification at 23°C a F/M-ratio of 0.25 kg BOD5/(kg VSS • d) or an aerobic sludge age
of 11 days was needed. These values are a result of low pH and low alkalinity
during the experiments in period 4 and 5. Model calculations - see chapter 6 have shown this. The values corrected for the low pH can be found in Table 7.2,
together with the design values at 17CC.
The low pH in the secondary effluent in the experiments, is due to the low
alkalinity (approx. 2,5 mmole/HC03") in combination with the high nitrogen
Fig.7.3.NNH3 and NN03 final effluents
vs F/M. T M 9 and 23 a C.
Average values periods 3,4,5.
en
OU
NH4N anc N03N In effluent (mg/l)
+
19«
40
30
X ""
. . . . _._1 9 * . _ : - - - .
20
00
""""■5
f
""-..
X
10
19"
n
19'
U "1
0.1
0.2a
¥~'~~
0.3
.a.
0.4
0.5
0.6
0.7
F/M (kg BOD/kg VSS.day)
+
CONV.NN
H 3
*
CONV.NN03
D
FMCT.NN
H 3
x
FMCT.NN03
Dashed lines indicate tendency at 232C
0.8
0.9
Fiq.7.4.N-NH3 in effluent vs Aerobic
sludge aqe.CONV and FMCT systems.
Data for periods 3 — 4 — 5 — 6 _ 7.
(mg/1)
50
Äft
+
-i"
40-1
•*-"fério(ls--6"7"'
30
2010-
Periods 3—4—5
ut
B.ft
oo
oo
#*
4 - 22.7%
+
+
22,8-°t
T
Labeled the teiiperatures for every
period.
+
lift
-4=-
20
Aerobic sludge age (days)
23.ft
"î"
aft
40
-89content of the raw wastewater (approx.40-50 mg N/1). The alkalinity consumption
of the nitrifiers (0.14 m mole H + / mg N oxidized is so high that if more than 10
mg NH4-N/1 is to be nitrified the alkalinity of the water needs to be increased
either by addition of base or through denitrification. Addition of base will not
solve problems with denitrification in settlers during summer, and the suspended
solids escape resulting from denitrification.
The results obtained with nitrification as given in Table 7.2 illustrate that the rate
of nitrification is within the normal range as long as pH is 7-7.5. In this range
nitrification proceeds with approximately twice the speed obtained at pH 6.2-6.8.
The normal range for the maximum growth rate of nitrifiers is around 0.8 d"1 at
20°C /Henze et al. 1987/
Table 7.2 Nitrification. Estimates for increased pH based on experimental results.
Maximum
F/M-ratio
kg BODj/kg VSS • d
Minimum
ox, aerobic
d
Experiments
0.25
Model, pH(7-7.5)
A, max
Temp.
d"1
°C
11
0.4
23
0.40
6
0.8
23
Model, pH(7-7.5)
0.30
9
0.6
20
Model, pH(7-7.5)
0.25
11
0.4
17
Figure 7.2 and 7.3 shows that there is no difference in nitrification in the two lines
investigated.
Table 7.3 shows measured and model calculated alkalinity changes during
nitrification in experimental period 4 and 5. It can be seen that the model predicts
the alkalinity change reasonably.
-90
Table 7.3. Alkalinity changes in biological process, period 4 and 5, mmol HC03"/1
Period 4
Period 5
CONV
FMCT
CONV
FMCT
Influent
(measured)
4.52
4.32
6.12
5.22
Effluent
(measured)
0.52
0.64
2.26
2.14
Effluent
(calculated)
0.00
0.00
0.00
0.00
7.2.2 Activated sludge quality
The specific oxygen uptake rate is similar in both lines in spite of the fact that the
FMCT-line was operated at higher MLSS concentrations (3-6 g/1) while the
CONV-line at lower concentration (0.6-3 g/1) - see Table 5.1. This is shown in
Figure 7.5. The observed values were approx. 10-20 mg 0 2 /(g VSS.h) in periods
4,5,6 and 7 which are within the expected range (Kristensen et al., 1992). The
activated sludge in the experiments have had a VSS/SS-ratio of 0.6-0.8, which is
in the expected range as well.
Sludge volume indexes as well as abundance of filamentous microorganisms varied
significantly during the experimental periods. The lowest SVI's were observed in
periods 4 and 5 characterized by high sludge age (and consequently low F/M
ratio). Both lines revealed at those periods average SVI's between 41 and 65
ml/g. The highest SVI's were observed in the CONV-line in periods 2,3 and 7, up
to 426 ml/g.
The relation between SVI and aerobic sludge age is shown in Figure 7.5 a. In
general, in the CONV-line the relation between SVI and aerobic sludge age is
hyperbolic. At aerobic sludge ages above approx. 10 days SVI's do not exceed 100
ml/g. In the FMCT-line the relation between SVI and sludge age is loose and
5 .. So ip e c iifif i c
ïq.7
/ .. b
M L V S S . CONV a n d
e rax.Q
r a t e \v :
o x y _ g e n u p tt a
a kk e
FMCf. P e r i o d s
4,5,6,7
50
40
L
0
_c
ui
30
D D
LO
en
o
en
E
\-/
D DD
20
DD
D
'P. u ,
a Q
D
D
□
CD
G
I
3D
en
□
rP
D
Sn D £
. . t l . p . BP . .
10
o fl D°nb
0
2000
D
_
§
n
4000
6000
r
8000
MLVSS ( m g / l ) .
N o t e : Values above 3.500 mg/1 of MLVSS belongs to t h e FMCT line, while values below
2.500 mg/1 belongs t o the CONV line.
-92-
Fig.7.5a Relation between SVI
and Aerobic Sludge Age
500
Sludge Volume Index (ml/g)
400
300
200
100
10
20
30
Aerobic sludge age (d)
-93rather insignificant. The SVI's vary between 41 and 167 ml/g. This is explained by
the large quantities of sludge accumulated in the FMCT-line big clarifier. Anaerobic conditions in the clarifier sludge layer presumably controlled occurrence of
both, Sphaerotilus natans and type 1701 which were the microorganisms most
drastically influencing SVFs as shown in Figure 7.5 b.
In all experimental periods biological foaming occurred but at different intensities.
Microscopic observations indicate the responsible microorganism - Nocardia sp.
As shown in Figure 7.5 c, Nocardia was present at all experimented sludge ages.
Haliscomenobacter hydrossis occurred in significant abundances at aerobic sludge
ages below about 20 days. Neither Nocardia sp. nor H. hydrossis influenced
significantly SVFs. Fungi appeared in the FMCT-line in period 1 as dominating
filaments without significant increase of SVI. During this period marked decrease
of pH was observed in FMCT-line. While pH in CONV-line was 7.4, in the
FMCT-line it was 6.8. Type 0041 occurred at small abundance in both lines during
several experimental periods without causing problems.
In general, the microscopic observations and SVI's were within the expected
occurrence described in the literature for completely stirred activated sludge
reactors. The single exception was Nocardia sp. which occurred at all situations at
significant abundances. That is not the usual case. Nocardia foam floated on
aeration tanks and covered their surface, in some periods almost completely. In
most periods no significant difference was observed between the two lines.
Average relative abundance through all periods was in CONV-line 3 and in the
FMCT line 2. This was influenced mainly by the two last periods, No 6 and 7.
These were characterized by low temperature, 8 °C, and no nitrification. The
main difference between the two reactors was the aerobic sludge age fraction.
While in the CONV-line the fraction was as high as 0.67-0.97, in the FMCT-line it
was only 0.31-0.83. Thus the recycled sludge dwelled for significant periods of
time in anaerobic conditions since no nitrification occurred at that time. On
contrary, during periods 4 and 5 the temperature was high, around 23 °C, and
nitrification occurred. The aerobic sludge age fraction in the FMCT-system was
94
Fig.7.5b Relation between Abundance of
Filaments and SVI
(Sphaerotilus n. and Type 1701 only)
500
Sludge Volume Index (ml/g)
400
300
200
100
1
2
3
4
5
6
Cummulative Relative Abundance
95
Fig.7.5c Occurence of Filamentous Microorganisms at Various Aerobic Sludge Ages
Nocardia
H. hydrossis
S. natans
T. 1701
10
20
30
Aerobic Sludge Age (d)
40
-96higher than in the low temperature periods, 0.7 compared to 0.3. The conditions
in the clarifier blanket were partially anoxic due to the nitrates present at high
concentrations. From these observations it could be concluded that keeping the
recycled sludge anaerobic for a period of time may contribute to suppressing
Nocardia sp.
This finding is supported by Mori et al., who found that an anaerobic-oxic process
controlled Nocardia sp. to acceptable levels. Process configuration, however, was
in their experiments quite different.
The S\Ts of the activated sludges influence the recycle solids concentrations as
shown on Figure 7.6. At high SVl's sludge failed to thicken sufficiently and low
concentrations of solids was recycled into the aeration tank. This resulted in low
mixed liquor concentrations (see Table 5.1 period 7, CONV line). For SVTs of
100 -150 ml/g, 8-12 g SS/1 can be expected in the return sludge in the CONV
line. The FMCT lines gives higher recycle solids (12-16 g SS/1) due to the higher
retention time. The solid line in Figure 7.6 illustrates that in the FMCT line
considerably higher recycle solids concentrations are obtained than those found in
the SVI test.
7.2.3 Settling velocity
The relationship between initial zone settling velocity and SVI has been investigated. The observed initial zone settling velocities vary from 0.1 - 4,3 m/h - see
Table 5.13. Using the approach by Daigger and Roper 1985, and the expression
V. = V 0 - e k ' X i
the data has been grouped in 4 ranges according to the SVI. Based on these 4
groups, the k-value for each group has been estimated and the result is shown in
Figure 7.7.
Fig.7.6.Recycle SS vs SVI.Recirculatiori
rates 30-78%.Solid line illustrates s o lids concentration in SVI test
Recycle SS (g/l).
CO
-J
"i
i
1
1
50
100
150
200
r
250
SVI (ml/g).
300
350
400
450
Fig.7.7. Settling velocity vs
MLSS for different SVI ranges.
Ln VI (m/h)
CD
oo
6
MLSS (g/l)
Range 1 - S V I 1 8 - 6 3
-B- Range 2-SVI 64-106
Range 3-SVI 110-208
- * - Range 4-SVI 3 5 3 - 8 3 5
Represented regression lines for
every range.
F i g . 7 . 8 . K vs SVI average in every
range.
2.5
.:+"
M
1.5
k tea
CO
(O
1
0.5 4
.+.
4
o
:
Too
K is the slope of regression lines
plotting In Vi vs HL5S.
~m
300
SVI (il/g)
400
500
600
- 100-
The figure illustrates, that for increasing SVI the initial settling velocity for a
given MLSS decreases. In Figure 7.8 the settling constant, k, has been plotted
against SVI. There is a good correlation between the two parameters. The k
values obtained in this study are shown in Table 7.4 together with the k values
found by Daigger & Roper, 1985. They measured stirred SVFs which gives lower
values than unstirred SVTs. Thus the sludge in the present experiments has a
somewhat lower settling velocity.
Table 7.4. Comparison of k-values obtained for settling characteristics.
SVI range
(Daigger & Roper)
36-64
65-108
111-251
285-402
k
0.25
0.32
0.52
0.85
SVI range
(experiments)
29-63
64-106
110-208
353-835
k (experiments)
0.14
0.42
0.66
2.33
k (modelling)
7.2.4 Effluent quality
The effluent quality will be discussed in two parts - the soluble and the suspended. The soluble concentrations will be a result of the influent and on the
biological processes in the treatment plant.
Soluble COD in the effluent can be divided in many fractions. Of primary interest
is the two fractions biodegradable and inert (non-biodegradable). The inert COD
concentration in the effluent can be estimated as:
CODincrt, „,„„,. = COD^,,,, - 1,5 • BODS«,,,,,.
Fiq.7.9.C0D inert (s)e vs C0D(s)i.
CONV and FMCT.— — — —
Average values periods 1 3 4~5 6 7.
COD inert (s) eff luent (mq/1).
150
200
COO (s) influent (mq/1).
COD inert soluble = COD soluble - 1.5 B0D5 soluble
-102In Figure 7.9 the correlation between effluent inert soluble COD and total soluble
COD in the influent is shown. It is seen that approximately 15 per cent of the soluble COD in the influent ends up as soluble inert COD in the effluent. The soluble inert COD in the effluent does not necessarily has its sole origin in the
soluble COD of the influent.
Possibly a part of it is a result of biomass decay (Artan et al., 1990), but as a
simplified approach the correlation given, in Figure 7.9 can be used.
Figure 7.10 shows that temperature and F/M-loading influences the total soluble
COD in the effluent. Increasing F/M-loading will increase soluble COD in the
effluent. Decreasing temperature has a similar effect. The observed increase in soluble COD can not be explained by the increase in soluble BOD in the effluent.
Figure 7.11 shows that BOD does only increase marginally. Thus there is an increase in inert soluble COD for both low temperature and high load. This fits well
with the observations by Sollfrank and al., 1992 that at low temperatures more
soluble inert is found in the effluent.
High load can in this respect be regarded equal to low temperature in the sense
that under both conditions the degradation of organic matter is less complete.
Figure 7.11 illustrates that removal of soluble BOD is very efficient under all the
investigated conditions. Total BOD in the effluent is shown in Figure 7.12 . For
all investigated F/M-loadings 0.15-0.60 kg BOD/(kg VSS • day) the total BOD is
below 20 mg/I and the total COD below 50 mg/1. Thus the quality of the effluent
with respect to organic matter can live up to the expected effluent criteria of 25
mg BOD/1 and 125 mg COD/1 according to the EEC directive (91/271/EEC) of
21 May 1991.
Fig.7.10.CODs in effluent vs F/M and T5.
Average values periods 4~5_6_7
60
CODs in effluent (mg/l)
50-
o
w
40
FMCT High T9
30-
**""C0NV-Iöw-T*- B - FMCT low Ts
-*-
?.0
0.1
0.2
Labeled the temperatures.
0.3
0.4
0.5
F/M (kg BOD/kg VSS.day)
CONVhighT-0
0.6
0.7
Fig.7.11.BODs in effluent vs F/M and T9.
Average values periods 4~5_6_7
BODs in effluent (mg/l)
o
0.1
0.2
Labeled the temperatures
0.3
0.4
0.5
F/M (kg BOD/kg VSS.day)
Fig.7.12.BODe vs F/M.
Average values periods 4 5 6 7
on
BODe (mg/l)
¿\J
J
I
X
i
15
4
FMCT
X
CONV
I
X
+
10
■
■
"
*
4
o
UI
■
X
4
X
5
.. _
o0.1
0.2
0.3
F/M (kg BOD/kg VSS.day)
0.4
0.5
0.6
106
In periods with bulking in the pilot plant, the effluent quality with respect to
suspended solids was excellent due to filtering of the effluent through the sludge
blanket This effect is difficult to obtain in full scale plants because of problems
with controlling the sludge blanket under storm water conditions.
7.2.5 Yield coefficient, activated sludge
The sludge production is strongly influenced by temperature and F/M-load. In
Figure 7.13 a and b it is shown that high load and low temperature increases
sludge production considerably. In Table 7.3 values relevant for design are given.
It is seen that for constant F/M of 0,2 kg BOD/(kg VSS-d) the sludge production
in winter (8°C) is twice as high as in summer (23°C). If the load is increased
during winter because of no need for nitrification, then the yield is 2,5 times that
during summer. There is no significant difference between the yield for the 2 lines
investigated as long as they are operated at similar F/M-ratios.
Table 7.5 Observed yield coefficients for the CONV and FMCT line.
F/M
Temp
kg BOD/
(kg VSS-d)
°C
kg VSS/kg
BOD
kg SS/kg
BOD
kg COD/kg
COD
0.20
23
0.23
0.32
0.20
0.20
17
-0.3
0.45
-0.27
0.20
8
0.41
0.65
0.36
0.40
8
0.54
0.78
0.48
Observed yield
There is a close relationship between the F/M-ratio and the aerobic sludge age as
expected. This is shown on Figure 7.13 c. No difference is seen between CONV
and FMCT line. This means that the regression line given in Figure 7.13 c can be
used to convert between F/M-ratio and aerobic sludge age as wanted.
Fi q.7.13a.Y observed vs F/M and T~.
CONV and-FMCT.
— - _ —
Yob:
Average values periods 3 4 5 6 7.
(kg VSS/kg BODreioved)
o-J
0.4
0.6
F/H (kg BOO/ kg VSS.day)
Fi q- 7.13b- Y observed vs F/M and T - .
CGNV and FMCT.
Average values periods 3 — 4 - 5 _ 6 _ 7.
i obs (kg TSS/kg BODrenoved)
o
00
A
0.6
F/M (kg B0Ü/ kg VSS.day)
FIG. 7.13 c
Reciprocal Aerobic Sludge Age v:
Average values all periods
-i—i
0.4
F/M.
i_
FMCT 1
-
CONV D
>,
-S
0.3
Ql
en
<
0.2
o
Ql
CO
t)
CD
D
m
JD
0
L
ai
<
0.1
0 -
-0.1
-i
i—■—■—■—r
0.2
0.4
0.6
F/M ( k g BOD/kg VSS.day)
0.8
-1107.2.6 Energy consumption
Energy consumption and yield is closely related. Figure 7.14 shows the specific air
consumption in the two lines. The air consumption is a function of 3 factors:
- yield;
- D.OinMLVSS;
- aeration efficiency.
It is seen that the air consumption is high when the yield is low. The energy
consumption for the same F/M ratio was approximately equal in both systems.
Since the CONV-line was operated in general at lower concentrations of dissolved
oxygen in the mixed liquor, the oxygen transfer was for this line higher by 10-15
%. This can not be easily seen from the data because of other factors influencing
the oxygen transfer rate as well, for instance significantly higher mixed liquor
solids concentration in the FMCT-line than in the CONV-line. The higher solids
concentration tends to increase oxygen transfer efficiency in the FMCT-line due
to a higher volumetric reaction rate. At the same time increased air flow in that
line has the opposite effect. The oxygen transfer efficiency in the pilot plant is in
general rather low (2-4 per cent), because of low water column depth in the
aeration tanks.
7.3 Secondary settling
The strongest influence on secondary settler performance in this study has been
the influence of nitrate. Nitrate causes denitrification in the settler, and nitrogen
bubbles may be produced which will tend to float the suspended solids. This
phenomena is called rising sludge. Figure 7.15 illustrates this effect. At low nitrate
concentrations (0-3 mg NCyN/l) the suspended solids concentration in the
effluent is stable and low, 5-20 mg SS/1. At nitrate concentrations above 6-8 mg
NO3-N/I suspended solids in the effluent gets unstable, and at higher levels, 15-50
F¡g.7.14. AIR CONSUMPTION VS YIELD.
AVERAGE VALUES PERIODS 4,5,6,7.
OKO
m3 air/Kg BOD5 removed
¿OU
200
150
100
•
■
+
\
■
---
4-
4_
50
o0.1
0.2
0.3
0.4
0.5
YIELD(Kg VSS/Kg BOD5 removed)
CONV
+
FMCT
0.6
0.7
Fig.7. 15 ..TSS vs N-N03 in final effluent
All values for periods 4 - 5 - 6 _ 7 .
J
i
i_
100 -
75
o
O O:
en
E
50
ai
en
co
O
< * ■ ■ ■
O
25
o
o
o
o
s>
•<£>•
o
oo
o o
D^va
:<$>
í
.o
So o
«> C0NV
O FMCT
0 ~i
10
20
1
r~
-I
30
N-N03e (mg/1)
1
I
1
40
1
1
1
I
50
-113-
mg SS/l. This illustrates that nitrogen bubble generation is not always found when
nitrate is high. Many factors influence the generation of nitrogen bubbles, among
others:
- nitrate concentration;
- denitrification rate (incl. temperature effects);
- solids retention time in the settler;
- nitrogen gas concentration in MLVSS;
- oxygen concentration in MLVSS.
The complicated interplay between these factors can not be solved through the
results of these investigations. But the results illustrate that nitrate in the effluent
might deteriorate the effluent quality with respect to SS, BOD5 and COD. Temperature and hydraulic retention time in the settler also effects SS in the effluent.
The temperature effect seen in figure 7.16 is mainly the effect of nitrate which is
found in the effluent at high temperatures. Increasing hydraulic retention time has
a minor impact and reduces SS. A similar minor impact is seen for the settler
overflow rate as shown in figure 7.17. In most cases this load has been low 0.1-0.7
m/h and for these loads only a slight effect would be expected.
The sludge blanket height does not seem to have had any effect on SS in the
effluent - see figure 7.18 and 7.19, as long as it is more than 1 m below the water
surface.
For all experiments there was no significant variation in performance of the
settlers in the FMCT and the CONV line. This is remarkable when considering
the difference in the design of the two settlers. It indicates that the operational
parameters compared - blanket height and overflow rate - seems to be general for
both types of settlers.
SSe (mg/1)
Fig.7.16.SS in effluent vs hydraulic
retention time in the secondary settler.
Average values for periods 4 — 5 — 6 — 7.
Hydraulic retention tine (h)
50
SSe (ig/l)
Fig.7.17.SS in effluent vs overflow rate
in secondary settler.
Average values for periods 4"5~6"7.
40302010-
.2
0.4
.8
1
1.2
Overflow rate (n/h)
1.4
1.
1.8
Fig.7.18.SS in effluent vs Blanket level
in secondary settler for CO NV system.
j
i—I—i
i i i I i i i i 1 i i i i i i i i ■ i i i i
i — L
i
i ■ ■ ■ i
120 110 4
100 -i
90 -\
80
70 -.
en
E
60 4
50
40
. D
30 -3
20
D D„ .
£>
10
*a*a
a•
0 -Ì
-T - T
1 1 1
1 1
0.5
1 T"
' I''''I '
1.5
2
2.5
H.BLANKET Cm)
Note: Data for periods 267 (no nitrification)
3.5
f IG.7. 19.SS in effluent vs Blanket leve
in secondary settler for FMCT system.
en
E
ai
in
tsi
120 110 \
100 \
90 -Ë
80 \
70 \
60 \
50 \
40 -j
30 \
20 \
10 \
0 -=
•••••••
' Q • ■•
Q
' ' '!' 'D' ' ■ ' " ' '
;
a ' '■ '
a
a ;
B'
V'
' 'jï' 'D' ' ' ' 'f '
•••••□
' b'n.* ' D ' n ' a ^ ' :
D ' ' '.
a
•
-i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—r
0.5
1.5
2
2.5
H.BLANKET Cm)
Note: Data for periods 267 (no nitrification)
3.5
D'
-
- 118
7.4.
HEAVY METALS
The pilot plant influent, the primary effluent, the secondary effluent and the
sludges were analyzed for heavy metals (Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn).
Starting from period 4 (July 90) the pilot plant influent was taken from the
influent to the full-scale primary treatment plant in Galindo. Since not yet all the
sewers connecting the wastewater from Bilbao to the treatment plant have been
constructed, the incoming wastewater does not represent the ultimate
composition.
Comparison of heavy metals content found in pilot-plant sludges and regulated by
EC Directive (86/278/CEE from 12.6.1986) is in Tab. 7.6. Metals are compared
to the maximum permissible concentrations in soils at low pH what is the most
strict standard for comparison. So far, the concentration of metals in the biologically treated wastewater and in the sludges are low in comparison to applicable standards. As can be seen from the table, all concentrations (except asingle
value of Ni in primary sludge) are within acceptable limits.
Tab.7.6. Concentration of metals found in pilot plant sludges
mg/kg of dry solids
Metal
Cadmium
EC regulation for
soils pH<7
Primary sludge
Secondary
sludge
20
2-5.9
3.9 -5.9
Copper
1000
152-492
75.5-347
Nickel
300
90.7-1057
66-249
Lead
750
91.5-218
126-236
Zinc
2500
471-1018
460-983
16
0.12-1.32
0.49-3.1
1000
27.6-136
25.8-46.6
Mercury
Chromium
-1197.5.
GENERAL WASTEWATER CHARACTERISTICS
The wastewater used in the experiments has characteristics similar to normal
municipal wastewater. This holds for the concentration of the various components and
the ratios between these. Toxic substances (e.g. metals) have not been observed to
influence the treatment results. However it must be pointed out that the wastewater
used is not identical to what will be treated in future in the full scale plant.
- 120 8.
CONCLUSIONS
8.1.
General conclusions
The primary settling is normal as expected with a SS removal of about 50% and
a COD removal of 25-35 per cent. The removal of inorganic suspended solids is
slightly higher than that of VSS.
The effluent quality with respect to BOD and COD is well below the proposed
EEC standards for both systems. The soluble inert COD in the effluent is approx.
30-40 mg/1.
Increasing F/M-ratio increases soluble COD in effluent. Decreasing temperature
has a similar effect.
To obtain nitrification at 23°C a F/M-ratio of 0.25 (kg BOD^/kg VSS.d) or an
aerobic sludge age of 11 days was needed. These values are a result of low pH
and low alkalinity during experiments. Calculated nitrification rates with an
activated sludge model for pH-(7-7.5) are normal so no additional inhibiroty
effects on nitrification was detected.
The strongest influence on secondary settler performance in this study has been
the influence of nitrate. Nitrate in effluent give problems in settler producing high
SS in the effluent.
Problems with low alkalinity and denitrification in settlers can be solved by
providing a process with nitrification and denitrification. COD/N-ratio in the raw
wastewater is sufficient for denitrification. In primary settled or precipitated
wastewater the ratio is rather low, which indicates that external carbon might be
added to satisfy part of the carbon demand for denitrification.
The secondary settling performances in the two systems are similar. FMCT gives
higher SS recycle concentration and provides higher stability in operation.
-121 The observed yield was similar for both systems for similar F/M ratios. The yield
is highly influenced by temperatures and F/M-ratio. For similar F/M-ratio the
yield at 8* C was approx. twice the yield at 23° C.
The sludge settling velocity was in the normal expected range.
The removal of phosphorus was within the expected range for removal of P
through biological sludge production, approx. 2 mg P/l.
The removal of N was approx. 8 mg N/1 due to surplus sludge production. In
periods with nitrification a similar amount was denitrified. The overall removal
was 10-30% which for the high range indicates some denitrification in periods
with nitrification.
Energy for aeration was practically equal for the two systems for similar F/Mratios. The energy consumption was lower at higher observed yields.
Activated sludgefilamentousbulking occurred in some periods. It has been shown
that increasing aerobic sludge age above approx. 10 days eliminated bulking
problems in the CONV system. On the other hand, the FMCT system never
suffered from extreme bulking.
Biological foaming caused by Nocardia sp. was rather intensive and a general
phenomena for the particular wastewater and systems configurations. It can be
concluded from the experiments that exposure of the sludge to anaerobic
conditions can significantly suppress occurrence of Nocardia sp.
The wastewater used in the experiments has characteristics similar to normal
municipal wastewater. This holds for the concentration of the various components
and the ratios between these. Toxic substances (e.g. metals) have not been
observed to influence the treatment results.
-1228.2.
New system versus traditional system
Over the expected benefits of the FMCT system the following conclusions can be drawn:
Allows for better adjustment of biomass to instantaneous needs due to storage of
large amounts of biomass in the big clarifier.
Aeration tank volume could be reduced by using high MLVSS concentrations
(normal range 3000-6000 mg VSS/1). Reduction of volume could be approx. 50%.
The clarifier volume of the FMCT system was approx. 3-3.5 times the volume
needed for the CONV secondary clarifier.
There is no reduction in energy consumption in aeration tanks for similar F/Mratio.
The effluent quality was not improved compared to CONV system.
Excess sludge volume was lower due to higher concentrations. Dry matter
production (yield) is similar in the two systems.
Sludge in FMCT was more stabilized with a lower percentage of VSS.
Less bulking and foaming problems occurred in FMCT system.
-1238.3.
Modelling
Model has shown to be a valuable tool for interpretation of experimental results
identifying irregularities in experimental data.
The results from model follow the experimental results, and the modelling has not
revealed any irregularities in the wastewater composition of Bilbao, nor in the
process performance of the pilot unit.
The model can describe the actual settler performance and the performance of
the biological reactors.
- 124LIST OF SYMBOLS
AS
=
Activated sludge
BODe
=
BOD effluent (mg/1)
BODr
=
BOD removed (Kg/day)
BODs
=
BOD soluble (mg/1)
CODe
=
Chemical Oxygen demand effluent (mg/1)
CODi
=
Chemical Oxygen demand influent (mg/1)
CODinert (s)
=
COD inert soluble (mg/1)
CODs
=
COD soluble (mg/1)
COD (s)i
=
COD soluble influent (mg/1)
CODT^
=
Particulate COD (mg/1)
DO
=
Dissolved Oxygen in aeration tank (mg/1)
Fexcess
=
Sludge wasted and lost (Kg VSS/day)
F/M
=
Food mass ratio (Kg BOD/Kg MLVSS. day)
H. Blanket
=
Blanket level in secondary settler (m)
K
=
Settling constant (volume/mass)
MLSS
=
Mixed liquor .suspended solids (mg/1)
MLVSS
=
Mixed liquor volatile suspended solids (mg/1)
MxO
=
Total sludge mass beginning of period (kg)
Mxl
=
Total sludge mass end of period (kg)
NVSS
=
Non volatile suspended solids (mg/1)
OUR
=
Oxygen uptake rate (mg O^l.h)
P.S.
=
Primary settler
Qi
=
Influent flow (m3/h)
Qr
=
Recycle flow (m3/h)
Qw
=
Sludge wasting flow (m3/h)
R
=
Regression coefficient
SS
=
Suspended solids (mg/1)
S.S.
=
Secondary settler
SSe
=
Suspended solids effluent (mg/1)
125
SSi
Suspended solids influent (mg/l)
SOUR
Specific oxygen uptake rate (mg 0 2 /g VSS.h)
SVI
Sludge volume index (ml/g)
TSS
Total suspended solids (mg/1)
u
Utilization rate (Kg BOD/Kg VSS.day)
Va
Aeration tank volume (m3)
Vi
Initial settling velocity (m/h)
vss
Volatile suspended solids (mg/1)
Vtotal
Total volume: aeration tank + secondary settler
Xa
Biomass concentration in aeration tank (kg MLVSS/m3)
Xi
Initial SS concentration (mass/volume)
Y
Yield coefficient
Yobs
Observed yield coefficient
Maximum specific growth rate autotrophs^"1)
ex
Total sludge age (days)
6a
Aerobic sludge age (days)
o
Beginning of intensive period
i
End of intensive period
All the symbols used for laboratory and plant parameters are included in chapter 3.
- 126 10.
REFERENCES
Abwassertechnologie (1988) Ed. E. Blitz and W. Czysz. Springer Verlag
Berlin 1988 ISBN 3-540-13038-1
Artan, N. D. Orhon and B. Beler Baykal (1990) Implications of
the Task Group Model-1. The effect of initial substrate concentration.
Wat.Res.,24, 1251-1258
Daigger, G.T and R.E Roper (1985) The relationship between SVI
and activated sludge settling characteristics J. WPCF, 5JZ, 859-866
Dupont, R., Henze, M. (1991) Modeling Of The Secondary
Clarifier Combined With The Activated Sludge Model No. 1. Preprint :
IAWPRC conf. on: Interactions of wastewater, biomass and reactor configurations in biological treatment plants. Copenhagen, 21-23 August, 1991.
Eikelboom D.H. and Van Buijsen H.j. (1981). Microscopic Sludge
Investigation Manual. IMG - TNO Report A94a, Delft.
Ekama G.A., Pitman, A.R., Smollen, M. and Marais, G.v.R.
(1984). Secondary settling tanks. Chapter 8 in: Theory, Design and Operation
of Nutrient Removal Activated Sludge Processes, pp. 8.1-8.14. Water
Research Commision, Pretoria, SA.
Gujer, W. (1991) Modeling Population Dynamics in Activated
Sludge Systems. Preprint : IAWPRC conf. on: Interactions of wastewater,
biomass and reactor configurations in biological treatment plants.
Copenhagen, 21-23 August, 1991.
Henze, M., C.P.L. Grady jr., W. Gujer, G.V.R Marais and
T. Matsuo (1987) Activated sludge model no. 1 IAWPRC Sci. Techn. Report
No.l, IAWPRC, London
Kristensen, G.H, P.E. Jørgensen, M. Henze (1992)
characterization of functional groups and substrate in activated sludge and
wastewater by AUR, NUR and OUR. Wat.Sci.Tech.
Mori, T., Itokazu, K., Ishikura, Y., Mishina, F., Sakai, Y. and
M. Koga (1991) Control of Actinomycetes Scum Production by an AnaerobicOxic Process. IAWPRC Specialized Conference on Interactions of
Wastewater, Biomass and Reactor Configuration in Biological Treatment
Plants, Copenhagen, 21-23 August.
127
Process Control manual for Aerobic biological waste-water
treatment facilities (1977). EPA - 430 / 9-77-006.
Sollfrank, U., J. Kappeler and W. Gujer (1992) Temperature
effects on wastewater characterization and the release of soluble inert organic
material. Wat. Sei. Tech.
Standard Methods for the Examination of Water and Wastewater
(1989). 17,h edition APHA, AWWA, WPCF.
Vesilind P.A. (1979). Treatment and disposal of wastewater
sludges. Ann Arbor Science, Ann Arbor, Mich.
-129
ANNEX 1
DRAWING AND PHOTOGRAPHS OF
THE PILOT PLANT AND LABORATORY
SECONDARY SETTLER
FINAL EFFLUENT TANKS
BLOWERS
INDUSTRIAL WASTES RECEPTION TANK
00
AERATION TANK
DISSOLVED OXYGEN, pH AND T?, METERS WITH
AUTOMATIC CLEANING
134
LABORATORY
\^-/W^f^í^i&}-
INDUSTRIAL WASTE DOSAGE TANK
.-v -^---^:-':^^-'
CONTROL PANEL
136
LABORATORY
137
LABORATORY
139
ANNEX 2
ANALITICA!. METHODS
-140ANNEX 2
DESCRIPTION OF THE ANALYTICAL METHODS
Analyses and tests were carried out by laboratory personnel
working shifts for six days a week, so that samples could be
analyzed immediately they were taken. A refrigeration system
was used to preserve the 24-hour composite samples of influent
and effluents from the plant.
The frequency with which analyses were made was the same as in
the transitional and intensive periods; the only change was the
humber of parameters during the various periods.
The analytical methods used as a reference were those of
"Standard Methods for the Examination of Water and Wastewater",
17th Edition, 1989, APHA, AWWA, WPCF.
Here follows a brief description of the analytical methods
which were used.
SST:
Total Suspended Solids dried at 103-1052C.
A known volume of a sample is filtered through a
standard glass fiber filter and the residue contained
in the filter is dried at 103-105SC to constant weight.
The increase in the filter weight represents the
suspended matter.
SSV:
Volatile Suspended Solids calcined at 550 s .
Volatile solids correspond with the weight loss
occurring when the residue resulting from the SST test
is calcined in a muffle furnace at a temperature of
550+50SC.
DBO T:
5
Biochemical Oxygen Demand during a 5-day
incubation period.
A sample is placed in a full, stoppered bottle and
incubated in the dark, at 20 9 C, in the presence of
micro-organisms, excess nutrients and dissolved oxygen
for 5 days. The dissolved oxygen (D.O.) is measured
initially and after incubation. The DBO is calculated
from the difference between the initial and final D.O.
levels.
-141 DBO S:
5
Biochemical Oxygen Demand, during a 5-day
incubation period, of the soluble portion of the
sample.
O.D. :
Dissolved Oxygen.
Dissolved oxygen was measured by means of an oxygen
membrane electrode.
DQO T:
Chemical Oxygen Demand (Total Sample).
A sample is put at reflux for 2 hours in a highly acid
solution together with a known excess quantity of
potassium dichromate (K Cr 0 ) . After digestion,
2 2 7
the potassium dichromate that remains unreduced is
titrated with ammonic ferrous sulphate to establish the
quantity of potassium dichromate consumed and the
oxidizable organic matter is calculated in terms of
oxygen equivalent.
DQO S:
Chemical Oxygen Demand (Soluble)
The soluble DQO is determined exactly the same way as
described above, except that the sample is filtered
through a membrane filter prior to analysis.
N-NH :
3
Ammoniacal Nitrogen
Zn sulphate and sodium hydroxide (pH approx. 10.5) are
added to the sample so as to allow eventual
interferences to precipitate; afterwards it is
filtered. A dissolution is prepared with a known volume
of the filtrate, to which Nessler reactant is added to
develop colour. Ammonia is measured calorimetrically.
NTK:
Total Kjeldah Nitrogen
This determination shows the addition of organic and
ammoniacal nitrogen. The sample is digested at A20 9 C by
means of sulphuric acid, potassium sulphate and a
selenium reactive mixture as a catalyst, so as to
convert the organic nitrogenated compounds into
ammoniacal compounds; afterwards, the ammonia is
distilled in an alkaline medium and absorbed with boric
acid. The NTK is measured carorimetrically by using
Nessler reactant for colour development.
N-NO :
Nitrates
3 The previously membrane-filtered sample, the whiting and
the standard are pipetted in test tubes placed in a
container with cold water. The following is added,
allowing for rest periods between additions, in this
sequence: urea sulphite, sulphuric acid, chromotropic
acid and sulphuric acid. After stoppering the tubes, the
contents is mixed and following a 45-minute rest period
the nitratres are measured calorimetrically.
- 142P-PO :
Orthophosphates
4 Active carbon is added to the sample, which is filtered
through a membrane (0.45 Jim) and then vanadate-molybdate
reactant is added for colour development. The
orthophosphates are finally determined by a calorimetrie
procedure.
P-TOTAL
Total Phosphor
The sample is digested with a nitric-sulphuric acid
mixture until white fumes appear, soda is added to
Phenolphthalein pink colour and neutralized with
sulphuric acid. Total phosphor is measured as orthophosphates, following the above-mentioned procedure.
ALCAL R:
Total Alkalinity
Potentiometrie titration of the sample at ambient
temperature up to pH = 3.7 by using previously
standardized HCl approx. 0.02N. The result is expressed
in mmol/1 CaCO .
3
A & G:
Oils and Greases
Dissolved or emulsified oil and grease are extracted
from a sample acidified by contact with
trichlortrifluorethane and determined gravimetrically.
CI:
Chlorides
Chlorides were determined by the argentimetrlc method.
The potassium Chromate may indicate the final valuation
point of chloride with silver nitrate. Silver chloride
precipitates quantitatively prior to the formation of
silver Chromate.
SULF T:
Total Sulphides
Sulphides are oxidized by excess iodide in an acid
solution. The iodine formed is titrated with a sodium
tiosulphate dissolution, using starch as final point
indicator. For removal of interferences a preliminary
ZnS precipitation treatment is carried out, followed by
filtration.
FENOLES
The acidified sample is distilled with H PO at pH = 4.0
3 4
in order to separate phenols from non-volatile
impurities. In the presence of potassium ferrocyanide,
distilled phenols react with 4-aminoantipyrine to form
an antipyrine coloured compound. This compound is
extracted from the aqueous solution by CHC1 and the
absorbance is measured at 460 nm.
3
- 143DETERG:
Anionic Déte rgents
Anionic detergent s are transferred with methylene blue
from an acquous s olution to an immiscible organic
compound to form a cationic coloured compound. This
process comprises three successive extractions from an
aqueous dissoluti on in an acid medium containing the
sample and an exc ess of methylene blue en chloroform
(CHC1 ) ending wi th an aqueous washing. The intensity
3
of blueing in the organic phase is observed in a
spectrophotometer at 652 nm, as a measure of anionic
detergents.
CN T:
Total Cyanides
The cyanhydric acid is liberated by distillation and
air purging of the acidified sample. The purpose of
distillation is to separate the HNC from eventual
interferences by organic and inorganic contaminants.
The HCN gas is caused to pass through an NaOH washing
solution, in which it is collected. The cyanide
concentration in the soda solution is determined by a
selective electrode.
METALS
Metals were determined by atomic absorption spectrophotometry.
Samples contain particles and organic material
requiring a treatment prior to analysis. Metals can be
found either inorganically or organically bound, in
particles o dissolved. A digestion was made before a
preliminary filtration. A digestion with nitric acid
took place for the following materials: calcium,
magnesium, cadmium, chrome, copper, iron, nickel,
manganese, lead and zinc. For mercury, a digestion was
made with potassium permanganate-sulphuric acid.
In the atomic absorption spectrophotometry, the sample
is aspirated towards a flame in which it is atomized.
A light beam traverses the flame, passes through a
monochromator towards a detector which measures the
amount of light absorbed by the element atomized in
the flame. The amount of energy absorbed at a
characteristic wavelength in the flame is proportional
to the concentration of the element to be analyzed in
the sample.
Determination of calcium, magnesium, cadmium, chrome,
copper, iron, nickel, manganese, lead and zinc was
made by direct aspiration towards an air-acetylene
flame. Mercury was determined by the cold-steam
technique.
- 144 OUR:
OUR
Oxygen Consumption Rate
Agitation of the sample in a partly-full bottle to
increase the D.O. concentration in the sample almost
to saturation. Filling of the 250 ml Winkler bottle
with the sample, insertion of the D.O. meter probe,
placing of the bottle on a magnetic agitator and
recording of the D.O. concentration at 30-second
intervals for 15 minutes or until the D.O.
concentration is limiting (1.0 mg/1).
sp:
Specific Oxygen Consumption Rate
Ratio of OUR in mg D.0./1 x hr to the SSV of the
sludge sample expressed in gr/1 and determined by
gravimetric techniques.
V Sed:
Settled Volume
After homogenizing the sample, pour it carefully into
a 1 litre test beaker and allow it to settle for 30
minutes, at the end of which the volume occupied by
the settled sludge is measured in ml.
SVI:
Sludge Volume Indez
Retio of V.S. after 30 minutes to the SST of the
sludge sample, as determined by gravimetry and
expressed in gr/1.
SED TEST:
Zonal Settling Speed
After homogenizing the sample, pour it carefully into
a 2 litre test beaker (41.5 cm high x 8 cm dia.) and
allow it to settle. Record the heights of the liquidsolid interface at. 5-minute intervals during the first
20 minutes, at 10-minute intervals till minute 60 and
at 30-minute intervals till minute 180. Plot the
height of the interface (in cm) against time (in
minutes) and determine the settling speed as the
maximum gradient ocurring within the first 10 minutes
approximately.
Esp.Grav.:
Specific Gravity
Record the temperature of the sludge sample and weigh
first 100 ml of it and then 100 ml of distilled water
at A 9 C. Specific gravity is the ratio of the weight of
the sample to the weight of water, multiplied by a
corrective factor of the sample temperature.
MICROSCOPIC ANALYSIS
Throughout the project,from 2 to 3 weekly observations
were made of the activated sludge in both lines with a
view to follow up changes ocurring in the sludge
during the various periods. During the "live"
observations, a counting was made both of protozoa and
filamentous micro-organisms. After completion of the
-145
counting, a sample was taken for GRAM and NEISSER
tinting and thus final identification of filamentous
bacteria.
The method used for identification of types of floes
and filamentous micro-organisms was that of D.H.
Eikelboom and H.J.J. Van Buijsen.
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