ID: Class: 12 Subject: Biology Topic: Microbes in Human Welfare Type: Case Study Year: 2025

Question:

Study the figure given below and answer the questions that follow. [Figure is implied: Secondary Sewage Treatment Plant showing Aeration Tank, Settling Tank, Activated Sludge, etc.]
  • (a) Identify the figure and state its importance.
  • (b) Why is air diffused into the aerator tank? Explain.
  • (c) (i) What changes take place in the settling tank ?
    OR
    (c) (ii) How is BOD related to organic matter present in the water ?