April 2011, Vol. 23, No.4
Test your knowledge of nutrient removal
Multiple Choice Questions:
What is the most common form of nitrogen in influent?
C. Organic nitrogen
Which of the following biological reactions is most sensitive to cold temperatures?
B. Enhanced biological phosphorus removal
Denitrification requires which of the following process conditions?
A. High inorganic carbon and low dissolved oxygen
B. High alkalinity and moderate temperature
C. Low dissolved oxygen and organic carbon
D. High dissolved oxygen and adequate nutrients
All of the following processes often use cydic aeration to nytrify and denitrify, except which one?
A. Trickling filters
B. Sequencing batch reactors
C. Phased oxidation ditches
D. Cyclically aerated activated sludge
Which one of these is an indicator of good enhanced biological phosphorus removal performance?
A. Low biochemical oxygen demand concentration in the effluent
B. High phosphorus content of mixed liquor
C. Increased oxygen consumption in aerobic zone
D. Negative oxidation-reduction potential readings in anoxic zone
Incomplete nitrification may be indicated by which of the following?
A. Low ammonia in the effluent
B. High ammonia in the influent
C. High nitrite in the effluent
D. High nitrate in the effluent
The integrated fixed-film activated sludge (IFAS) process is a modification of the activated sludge process to do which of the following?
A. Provide effluent filtration
B. Increase dissolved oxygen concentration
C. Remove heavy metals
D. Increase biomass concentration
What is the concentration of alkalinity (as calcium carbonate) formed during the denitrification of 20 mg/L of nitrate–nitrogen?
B. 70 mg/L
C. 152 mg/L
D. 7.2 mg/L
Denitrification can be enhanced by all except which of the following?
What is the concentration of total phosphorus in plant effluent, if the plant effluent contains 0.5 mg/L orthophosphorus and 10 mg/L total suspended solids? Assume organic phosphorus is 1 mg/L and phosphorus content of the mixed liquor is 5%.
A. 1.5 mg/L
B. 2.0 mg/L
C. 7.5 mg/L
D. 11.5 mg/L
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Questions excerpted from the Biological Nutrient Removal Operation Study Guide, published in 2005 by the Water Environment Federation (Alexandria, Va.) and the American Society of Civil Engineers/Environmental and Water Resources Institute (Reston, Va.).