Concept of Primary Sludge

Q. (a) Three water samples A, B, C are collected. Their BOD was found to be 20mg/L, 8mg/L and 400mg/L respectively. Which sample is most polluted? Give reasons.
(b) At which stage of sewage treatment is BOD of effluent reduced? [3]

Q. FOAM and the biologists from humboldt state university, california created an integrated waste water treatment, they use plants for purify mainly :-

1. Sludge from water
2. Nitrate and phosphate from water
3. Heavy metals from water
4. All of the above

Q. Effluent of the primary treatment can increase the BOD of any water body.

1. False
2. True

Q. IRRI proposed which one of the following for the prevention of fertilizers pollution in agriculture?

1. Trickling filter method
2. None of the above
3. Mudball technique
4. Both A and B

Q. Effluent of the primary treatment can increase the BOD of any water body.

1. True
2. False