Question

Secondary sewage treatment is mainly a

• A. Mechanical process
• B. Chemical process
• C. Biological process
• D. Physical process

Answer 1

The correct option is C Biological process

In secondary or biological treatment of municipal waste rich in sewage, the organic matter is decomposed with the help of microbes. Decomposition of organic matter occurs by one of the three methods – water hyacinth pond, trickling filter method and activated sludge method. After decomposition, the treated water is sterilised through chlorination.