why is sludge is passed through the aerated tank ?
for class 7
Answers
Explanation:
The activated sludge process is a type of wastewater treatment process for treating sewage or industrial wastewaters using aeration and a biological floc composed of bacteria and protozoa.
Answer:
Wastewater is passed through bar screens which remove large objects like rags, sticks, cans, plastic packets, napkins etc.
Water then goes through Grit and Sand removal tank, where sand, grit and pebbles settle down.
Water is then allowed to settle in a tank where solids like faeces (called sludge) settle at the bottom and are removed with a scraper. A skimmer removes the floatable solids like oil and grease. Water so cleared is called clarified water. Sludge is used to produce biogas.
Clarified water is then passed through an aerator tank where air is pumped into the water. It helps aerobic bacteria to grow which decompose organic matter like human waste.
After several hours, the suspended microbes settle at the bottom of the tank as activated sludge. The water is then removed from the top. The dried activated sludge is used as manure.
Water is removed from the top and is stored in a tank. The treated water has low level of organic material and suspended matter. It is discharged into a sea, a river or into the ground. Sometimes it is disinfected through chemicals like Chlorine and ozone and then distributed to towns.