In sewage treatment, the detention period allowed for oxidation ponds ranges from __________ weeks.

The detention period for oxidation ponds is usually kept as

A

48 hours

B

24 hours

C

10 to 15 days

D

3 months

During sewage treatment, the sewage is subjected to __________ treatment in Imhoff tank.

A

Filtration

B

Digestion

C

Sedimentation

D

Both B and C

Bacterial aerobic oxidation of polluted water in biological oxidation ponds is done to purify it. Presence of bacteria helps in

A

Coagulation and flocculation of colloids

B

Oxidation of carbonaceous matter to CO₂

C

Nitrification or oxidation of ammonia derived from breakdown of nitrogeneous organic matter to the nitrite and eventually to the nitrate

D

All of the above

Fine grit present in sewage is removed in the __________ during sewage treatment.

A

Grit chamber

B

Detritus tank

C

Trickling filter

D

Skimming tank

__________ substances present in sewage are removed in grit chamber during sewage treatment.

A

Organic

B

Fatty

C

Inorganic

D

Dissolved

In a sedimentation tank, the detention period for water ranges from __________ hours.

A

2 to 4

B

8 to 12

C

16 to 20

D

24 to 32

Biological oxidation ponds remove organic matters present in the polluted water by

A

Using the activities of bacteria and other micro organisms

B

Aerobic oxidation

C

Both A & B

D

Neither A nor B

Aerobic biological oxidation ponds used for the purification of polluted water

A

Destroys/removes pathogen from the sewage

B

Is not very effective for nonbiodegradable substances (e.g. ABS) containing effluents

C

Destroys/removes pathogen much more effectively if the sewage is chlorinated

D

All of the above

If a person can save TK.380 in 5 weeks, in how many weeks, at this same rate, can the person save 2.6 times amount ?

A

13

B

12.5

C

11

D

10.6

If Mr. Azad can save Tk. 380 in five weeks , in how many weeks m at this same rate, can he save 2.6 times of this amount?

A

13 weeks

B

12.5 weeks

C

11 weeks

D

8 weeks

In sewage treatment, the detention period allowed for oxidation ponds ranges from __________ weeks.

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