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Secondary sewage treatment is mainly a
A
Biological process
B
Physical process
C
Mechanical process
D
Chemical process
Detailed Solution
Primary treatment is a physical process: floating debris is removed by filtration and grit by sedimentation.
In secondary treatment the primary effluent is passed into aeration tanks, where aerobic microbes grow vigorously into flocs (masses of bacteria associated with fungal filaments).
These microbes consume the major part of the organic matter in the effluent, which greatly reduces its BOD.
The sludge is then digested by anaerobic bacteria in anaerobic sludge digesters, producing biogas.
Since the work is done by microorganisms, secondary treatment is called biological treatment.
Hence secondary sewage treatment is mainly a biological process.
In secondary treatment the primary effluent is passed into aeration tanks, where aerobic microbes grow vigorously into flocs (masses of bacteria associated with fungal filaments).
These microbes consume the major part of the organic matter in the effluent, which greatly reduces its BOD.
The sludge is then digested by anaerobic bacteria in anaerobic sludge digesters, producing biogas.
Since the work is done by microorganisms, secondary treatment is called biological treatment.
Hence secondary sewage treatment is mainly a biological process.