Wastewater Treatment MCQ – Environmental Engineering

21. COD/BOD ratio of waste water is

1. 1/2
2. 3/4
3. 1
4. more than 1

22. B.O.D. of treated water should be

1. 10 PPM
2. 20 PPM
3. 30 PPM
4. Zero

23. For discharging sewage and industrial effuents into stream, 5 day BOD at 20°C should not exceed

1. 30 mg/L
2. 50 mg/L
3. 100 mg/L
4. 200 mg/L

24. Say a raw waste water sample from AAWWTP has 5-day BOD equals to 2000 mg/L (reaction constant k = 0.23/day at 20°C). Calculate value of ultimate BOD?

1. 2296 mg/L
2. 2826 mg/L
3. 2926 mg/L
4. 2000 mg/L

25. For the COD test of sewage, organic matter is oxidized by potassium dichromate (K₂Cr₂0₇) in the presence of

1. Nitric Acid
2. Sulphuric Acid
3. Hydrochloric Acid
4. Acetic Acid

26. The absorbent most commonly used in water and waste treatment is

1. Sand of grain size from 0.1 to 2 mm
2. Activated carbon granules of size 0.1 to 2 mm
3. Ordinary wood shavings of fine size
4. Coal-tar

27. What is the function of Aerobic Biological Attached Growth Process in waste water treatment?

1. Conversion of suspended organic matter into settleable biofloc and stable inorganics.
2. Removal of organic settleable solids.
3. Conversion of organic matter into CH₄ & CO₂ and relatively stable organic residue.
4. Removal of inorganic suspended solids

28. If the sewage contains greases and fatty oils, they can be removed in

1. Sedimentation tanks
2. Grit chambers
3. Aeration tanks
4. Skimming tanks

29. During the second stage of anaerobic digestion of waste water, it is necessary to maintain proper

1. Pressure
2. Impurities
3. Volume
4. pH

30. The purpose of equalization basin in waste water treatment plant is to

1. Filter oils
2. Absorb fluctuation of flow rate
3. Equalize amount of organic matters
4. Remove sludge