What is the key difference between primary and secondary sewage treatment?
Assertion (A): Secondary sewage treatment involves mechanical agitation to promote microbial activity. Reason (R): Primary effluent is passed into large settling tanks where it is constantly agitated mechanically.
Correct answer: C — If assertion is true but reason is false.
NCERT confirms secondary treatment uses mechanical agitation (Assertion true). However, NCERT states “Primary effluent is passed into large aeration tanks where it is constantly agitated mechanically” - the Reason incorrectly places this in settling tanks instead of aeration tanks, making it false. This tests understanding of where mechanical agitation occurs in the treatment process.
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