. Secondary sewage treatment is mainly a

A: Biological process

B: Physical process

C: Mechanical process

D: Chemical process


Best Answer


  • Sewage pollution can be avoided by treating sewage in a sewage or effluent treatment plant before it enters the water supply.
  • Primary treatment, secondary treatment, and tertiary treatment are the three stages of sewage treatment.
  • Shredding, churning, flotation, screening, and sedimentation are the first steps in the treatment process.
  • By flowing through a water hyacinth pond, trickling filter method, or activated sludge method, organic waste is degraded by microbes and sewage fungus in secondary treatment. Sludge oxidation is aided by aeration.
  • The physico-chemical therapy tertiary treatment is used to remove turbidity and dissolved contaminants

Final Answer : The correct option is A. Biological process.

  • The biological method is primarily used in secondary sewage treatment. Primary wastewater is poured into enormous aeration tanks in secondary treatment, where it is mechanically agitated and air is pumped in. 
  • This promotes the rapid growth of beneficial aerobic microorganisms in flocs. The masses of bacteria connected with fungal filaments to form fonn mesh-like structures are known as flocs. While growing, these microorganisms absorb the majority of the organic materials in the effluent.
  •  The BOD (Biological Oxygen Demand) of the effluent is greatly reduced as a result of this. Following BOD reduction, wastewater is fed through an activated sludge settling tank, where bacterial floes are allowed to settle. The bacteria and fungi in this sludge are digested by an aerobic bacterium present in the huge tank.



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