Sewage Treatment and Disposal
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T E A C H E R S '
G U I D E
Sewage Tr eatm en t and Dispo sal Natur al Pur ification 96 per cent of pollution is remo ved by sewage treatm ent. However, once th e effluent h as been retu rned to th e water cycle it contin u es to be cleaned by processes of natural purification. • When water is stored in la kes an d pon ds, solid particles settle to the bottom. • Harm ful ba cteria gradu ally die out. • Algae can reduce hardness. • Tumbling over rocks or falling down waterfalls puts valuable oxygen into th e water. This encou rages water life an d oxidises organic im purities which im proves taste and smell. • Water is filtered natu rally as it seeps throu gh soil and rocks. Follow-Up Idea s • Make a m ini settling tan k a) Pu t 2-3 spoonfuls of soil into a jam jar of water. b) Stir well and leave to settle. c) The sedimentation process will produce well defined, gradu ated layers with coa rse particles at the bottom an d fine on es at the top. • Separating substances a) Pu t a m ixture of san d an d salt into a beaker of water an d m ix well. Th e soluble salt will dissolve in the wa ter, the in soluble sand will not. b) Th e solids can b e separated out by pourin g the solution throu gh a filter paper. The salt will pass throu gh in solution and the sand will be left on the paper. The salt itself can be rem oved from th e solution by evapora tion. • Arrange a visit to your local sewage treatment works. Fascinating Facts The Rom an s used five tim es as mu ch water as Lon don ers do today. Their sewage an d drain age system s were as good a s th ose of a m odern city. Water is one of the m ain carriers of disease. Accordin g to th e United Nation s, 25,000 people throughout the world die every day from diseases related to dirty wa ter. The largest Severn Trent sewage treatmen t works is at Minworth, n ear Birm ingh am , treating the sewage of m ore tha n a m illion people. Benton Green works at Solihull treats the sewage of just 100 people.
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G U I D E
Sewage Tr eatm en t and Dispo sal Natur al Pur ification 96 per cent of pollution is remo ved by sewage treatm ent. However, once th e effluent h as been retu rned to th e water cycle it contin u es to be cleaned by processes of natural purification. • When water is stored in la kes an d pon ds, solid particles settle to the bottom. • Harm ful ba cteria gradu ally die out. • Algae can reduce hardness. • Tumbling over rocks or falling down waterfalls puts valuable oxygen into th e water. This encou rages water life an d oxidises organic im purities which im proves taste and smell. • Water is filtered natu rally as it seeps throu gh soil and rocks. Follow-Up Idea s • Make a m ini settling tan k a) Pu t 2-3 spoonfuls of soil into a jam jar of water. b) Stir well and leave to settle. c) The sedimentation process will produce well defined, gradu ated layers with coa rse particles at the bottom an d fine on es at the top. • Separating substances a) Pu t a m ixture of san d an d salt into a beaker of water an d m ix well. Th e soluble salt will dissolve in the wa ter, the in soluble sand will not. b) Th e solids can b e separated out by pourin g the solution throu gh a filter paper. The salt will pass throu gh in solution and the sand will be left on the paper. The salt itself can be rem oved from th e solution by evapora tion. • Arrange a visit to your local sewage treatment works. Fascinating Facts The Rom an s used five tim es as mu ch water as Lon don ers do today. Their sewage an d drain age system s were as good a s th ose of a m odern city. Water is one of the m ain carriers of disease. Accordin g to th e United Nation s, 25,000 people throughout the world die every day from diseases related to dirty wa ter. The largest Severn Trent sewage treatmen t works is at Minworth, n ear Birm ingh am , treating the sewage of m ore tha n a m illion people. Benton Green works at Solihull treats the sewage of just 100 people.
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