Which one of the following gases is most significant as air pollutant ?

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Which of the following pumps in used to pump sewage solids with liquid sewage without clogging the pump is ?

A. Centrifugal pump B. Pneumatic ejector C. Reciprocating pump D. None of these...

In trickling filter, B.O.D. is reduced to___________________?

A. 30 to 40% B. 40 to 60% C. 60 to 80% D. 80 to 90%...

The recommended detention period for grit chambers is_______________?

A. 1 minute B. 2 minutes C. 3 minutes D. 5 minutes...

Before discharging the foul sewage into rivers, it is generally treated by_____________________?

A. Screening B. Sedimentation C. Oxidation D. All the above...

3.0 ml of raw sewage is diluted to 300 ml. The D.O. concentration of the diluted sample at the beginning of the test was 8 mg/l. After 5 day-incubation at 20°C, the D.O. concentration was 5 mg/l. The BOD of raw sewerage is______________________?

A. 100 mg/l B. 200 mg/l C. 300 mg/l D. 400 mg/l...