This set of Waste Water Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Phosphorus Removal – 1”.
1. Phosphorus is one of the responsible factors for eutrophication.
a) True
b) False
View Answer
Explanation: Controlling phosphorous discharged from municipal and industrial wastewater treatment plants is a key factor in preventing eutrophication of surface waters.
2. What is the percentage of sludge in phosphorus removal by chemical precipitation?
a) 10%
b) 20%
c) 30%
d) 40%
View Answer
Explanation: Phosphate removal is currently achieved largely by chemical precipitation, which is expensive and causes an increase in sludge volume by up to 40%.
3. What is the amount of phosphorus present in municipal wastewater?
a) 1-2 mg/L
b) 2-8 mg/L
c) 4-12 mg/L
d) 5-20 mg/L
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Explanation: Municipal wastewaters may contain from 5 to 20 mg/l of total phosphorous, of which 1-5 mg/l is organic and the rest in inorganic. The individual contribution tends to increase because phosphorous is one of the main constituents of synthetic detergents.
4. Phosphorus is the main component of synthetic detergents.
a) True
b) False
View Answer
Explanation: The individual contribution tends to increase because phosphorous is one of the main constituents of synthetic detergents. The individual phosphorous contribution varies between 0.65-4.80 g/inhabitant per day.
5. What is the average phosphorus contribution per person per day?
a) 1.2 g
b) 2.18 g
c) 3.26 g
d) 4.25 g
View Answer
Explanation: The individual phosphorous contribution varies between 0.65 and 4.80 g/inhabitant per day with an average of about 2.18 g.
6. What is the phosphorus available for a biological process called?
a) Phosphate
b) Orthophosphate
c) Polyphosphate
d) Biophosphorus
View Answer
Explanation: Orthophosphates are available for biological metabolism without a further breakdown. Molecules with two or more phosphorous atoms, oxygen and in some cases hydrogen atoms combine in a complex molecule to form polyphosphates.
7. ________ undergo hydrolysis and revert to the orthophosphate forms.
a) Biophosphorus
b) Orthophosphate
c) Phosphate
d) Polyphosphate
View Answer
Explanation: Molecules with 2 or more phosphorous atoms, oxygen and in some cases hydrogen atoms combine in a complex molecule. Usually, polyphosphates undergo hydrolysis and revert to the orthophosphate forms. This process is usually quite slow.
8. How much amount of phosphorus is removed by secondary treatment?
a) 0.2-0.3 mg/l
b) 0.4-0.6 mg/l
c) 0.5-1 mg/l
d) 1-2 mg/l
View Answer
Explanation: Normally secondary treatment can only remove 1-2 mg/l, so a large excess of phosphorous is discharged in the final effluent, causing eutrophication in surface waters.
9. ______ is present in EBPR implementations.
a) Aeration tank
b) Anaerobic tank
c) Aerobic and anaerobic tank
d) No tanks
View Answer
Explanation: Both aerobic and anaerobic is present in EBPR implementations. Enhanced biological phosphorus removal is applied to activated sludge systems for the removal of phosphate.
10. What does PAO stand for?
a) Poly-ammonium oxygenate
b) Polyphosphate-accumulating organisms
c) Poly-ammonium organisms
d) Phosphate-ammonium organisms
View Answer
Explanation: A group of heterotrophic bacteria, called polyphosphate-accumulating organisms (PAO) are selectively enriched in the bacterial community within the activated sludge.
11. What is the percentage of phosphorus present in bacterial biomass?
a) 0.2%
b) 0.3%
c) 0.8%
d) 1%
View Answer
Explanation: The percentage of phosphorous is 1-2 in all the bacterial biomass. A fraction of phosphorous is present in all the bacterial biomass.
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