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Question
Describe how do 'flocs' and 'activated sludge' help in Sewage Treatment.
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Solution
After the primary treatment, the primary effluent is taken for secondary treatment where it is passed into large aeration tanks and is constantly agitated and air is pumped into it. This leads to the vigorous growth of useful aerobic microbes into flocs. Flocs are masses of bacteria associated with fungal filaments to form mesh like structures. These microbes in the flocs consume the major part of the organic matter in the effluent and reduces the BOD (biological oxygen demand) of the effluent. Less BOD means that the waste water is less polluted.
After this, the effluent is passed into a settling tank where the flocs are allowed to settle and this sediment is called activated sludge. A small part of the activated sludge is pumped back to serve as the inoculum. Inoculum is the small amount of a material containing microbes that can start a new culture. This way same microbial culture is recycled and reused to start a new culture for the treatment.
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RELATED QUESTIONS
Three water samples namely river water, untreated sewage water and secondary effluent discharged from a sewage treatment plant were subjected to BOD test. The samples were labelled A, B and C; but the laboratory attendant did not note which was which. The BOD values of the three samples A, B and C were recorded as 20 mg/L, 8 mg/L and 400 mg/L, respectively. Which sample of the water is most polluted? Can you assign the correct label to each, assuming the river water is relatively clean?
What is primary treatment of sewage?
Answer the following question.
What are ‘flocs’, formed during secondary treatment of sewage?
What would happen if oxygen availability to activated sludge flocs is reduced?
Activated sludge should have the ability to settle quickly so that it can ______.
Why is aerobic degradation more important than anaerobic degradation for the treatment of large volumes of waste waters rich in organic matter. Discuss.
Removal of suspended, floating, coarse and solid particles in sewage treatment is called ______.
Biochemical Oxygen Demand (BOD) serves as an indirect measure of which water quality parameter?
Which action plans were initiated by the Ministry of Environment and Forests to construct sewage treatment plants and protect major Indian rivers from pollution?
Approximately what percentage of suspended solids is removed during primary sedimentation in a sewage treatment plant?
