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Tuesday, September 23, 2008

Water & Sewage treatment

Water treatment
• Water is collected from reservoirs or wells
• Flocculation removes suspended particles such as clay
• Filtration removes larger particles and protozoans as well as many bacteria
• Water is then treated with chlorine or ozone to remove pathogens and other microorganisms

Sewage treatment
• Primary treatment
– Sewage is held in settling tanks
– Heavy particles settle out
– Lighter particles are skimmed off the top
• Secondary treatment
– Sewage is aerated
– Bacteria grow and use organic matter to lower the BOD
– Activated sludge
– Trickling filters
Sewage treatment …
• Disinfection and release
• Sludge digestion
anaerobic digestion produces methane

Sewage treatment …
• Septic tanks
• Oxidation ponds
• Tertiary treatment
– All nutrients are removed and water is used for drinking

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