Part 2) grade 4 wastewater operator
certification practice test with correct
questions and answers
In the enhanced-biological-nutrient-control activated sludge system for the process control of
phosphorus removal, what are the primary controlling variables for the desired microbial
population?
a. volatile fatty acids b. soluble BOD5 and phosphate c. pH and alkalinity d. oxidized nitrogen and DO -
CORRECT ANSWERS-d. oxidized nitrogen and DO
In the four-stage Bardenpho process, ammonia from the influent is converted to nitrate in which area?
a. anoxic zone b. aeration basin c. anaerobic zone d. aerobic zone - CORRECT ANSWERS-b. aeration basin
. What is the theoretical amount of oxygen in milligrams required to convert 1 mg of ammonia nitrogen
to nitrate nitrogen?
a. 2.5 mg b. 3.3 mg c. 4.6 mg d. 7.1 mg - CORRECT ANSWERS-c. 4.6 mg
What is the operating guideline in the four-stage Bardenpho process for the mean cell residence time?
a. 15 to 20 days b. 20 to 25 days c. 20 to 30 days d. 20 to 40 days - CORRECT ANSWERS-c. 20 to 30 days
The optimum pH range in the enhanced chemical nutrient control reactions for phosphorus removed by
Fe3+ addition is
a. 4.0 to 6.0 b. 4.5 to 6.0 c. 4.5 to 6.5 d. 5.0 to 6.5 - CORRECT ANSWERS-a. 4.0 to 6.0
,What is the desired DO level for an anaerobic selector?
a. 0.05 mg/L b. 0.10 mg/L c. 0.15 mg/L d. 0.20 mg/L - CORRECT ANSWERS-b. 0.10 mg/L
Which one of the following types of foam is the most persistent and most difficult to control?
a. solids from the dewatering process b. filamentous or Nocardia organisms c. polymer overdosing d.
nutrient deficiencies - CORRECT ANSWERS-b. filamentous or Nocardia organisms
In the reaction of hydrogen sulfide with chlorine to form sulfuric acid, it takes one part hydrogen sulfide
for every _______ parts of chlorine.
a. 2.5 b. 4.5 c. 6.5 d. 8.5 - CORRECT ANSWERS-d. 8.5
. Dichloramine will be present in wastewaters at pH values below what?
a. 5.5 b. 5.0 c. 4.7 d. 4.3 - CORRECT ANSWERS-a. 5.5
What is the recommended withdrawal of chlorine from a 100- or 150-lb cylinder for each degree
Fahrenheit ambient temperature such that freezing does not occur?
a. 1 lb b. 2 lb c. 3 lb d. 4 lb - CORRECT ANSWERS-a. 1 lb
What chlorine emergency repair kit is used to stop leaks only at the valves of tank cars?
a. emergency repair kit A b. emergency repair kit B c. emergency repair kit C d. emergency repair kit T -
CORRECT ANSWERS-c. emergency repair kit C
, If a liquid sulfonator was misting, what would most likely be the cause?
a. loss of water pressure b. wrong size injector valve c. dirty injector valve d. defective evaporator -
CORRECT ANSWERS-d. defective evaporator
To prevent reliquefaction of sulfur dioxide gas in a conducting pipe, what should the temperature range
of the room be?
a. 60 to 80°F b. 70 to 85°F c. 80 to 90°F d. 90 to 100°F - CORRECT ANSWERS-c. 80 to 90°F
If the floc is too small in the solids removal physical-chemical treatment process, what is the most
probable cause?
a. paddle speed of flocculators too slow b. not enough dilution water c. improper or misaligned baffling
d. change in pH - CORRECT ANSWERS-d. change in pH
If the floc is too small in the solids removal physical-chemical treatment process, what is the most
plausible solution?
a. increase paddle speed of first flocculator b. add a coagulant aid c. check dosage with jar test d.
increase detention time by pumping out sludge - CORRECT ANSWERS-c. check dosage with jar test
If the floc is too large and thus settles too soon in the solids removal physical-chemical treatment
process, what is the most probable cause?
a. too much dilution water b. chemical makeup is too strong c. excessive addition of coagulant aid d.
cross-collectors not functioning - CORRECT ANSWERS-b. chemical makeup is too strong
certification practice test with correct
questions and answers
In the enhanced-biological-nutrient-control activated sludge system for the process control of
phosphorus removal, what are the primary controlling variables for the desired microbial
population?
a. volatile fatty acids b. soluble BOD5 and phosphate c. pH and alkalinity d. oxidized nitrogen and DO -
CORRECT ANSWERS-d. oxidized nitrogen and DO
In the four-stage Bardenpho process, ammonia from the influent is converted to nitrate in which area?
a. anoxic zone b. aeration basin c. anaerobic zone d. aerobic zone - CORRECT ANSWERS-b. aeration basin
. What is the theoretical amount of oxygen in milligrams required to convert 1 mg of ammonia nitrogen
to nitrate nitrogen?
a. 2.5 mg b. 3.3 mg c. 4.6 mg d. 7.1 mg - CORRECT ANSWERS-c. 4.6 mg
What is the operating guideline in the four-stage Bardenpho process for the mean cell residence time?
a. 15 to 20 days b. 20 to 25 days c. 20 to 30 days d. 20 to 40 days - CORRECT ANSWERS-c. 20 to 30 days
The optimum pH range in the enhanced chemical nutrient control reactions for phosphorus removed by
Fe3+ addition is
a. 4.0 to 6.0 b. 4.5 to 6.0 c. 4.5 to 6.5 d. 5.0 to 6.5 - CORRECT ANSWERS-a. 4.0 to 6.0
,What is the desired DO level for an anaerobic selector?
a. 0.05 mg/L b. 0.10 mg/L c. 0.15 mg/L d. 0.20 mg/L - CORRECT ANSWERS-b. 0.10 mg/L
Which one of the following types of foam is the most persistent and most difficult to control?
a. solids from the dewatering process b. filamentous or Nocardia organisms c. polymer overdosing d.
nutrient deficiencies - CORRECT ANSWERS-b. filamentous or Nocardia organisms
In the reaction of hydrogen sulfide with chlorine to form sulfuric acid, it takes one part hydrogen sulfide
for every _______ parts of chlorine.
a. 2.5 b. 4.5 c. 6.5 d. 8.5 - CORRECT ANSWERS-d. 8.5
. Dichloramine will be present in wastewaters at pH values below what?
a. 5.5 b. 5.0 c. 4.7 d. 4.3 - CORRECT ANSWERS-a. 5.5
What is the recommended withdrawal of chlorine from a 100- or 150-lb cylinder for each degree
Fahrenheit ambient temperature such that freezing does not occur?
a. 1 lb b. 2 lb c. 3 lb d. 4 lb - CORRECT ANSWERS-a. 1 lb
What chlorine emergency repair kit is used to stop leaks only at the valves of tank cars?
a. emergency repair kit A b. emergency repair kit B c. emergency repair kit C d. emergency repair kit T -
CORRECT ANSWERS-c. emergency repair kit C
, If a liquid sulfonator was misting, what would most likely be the cause?
a. loss of water pressure b. wrong size injector valve c. dirty injector valve d. defective evaporator -
CORRECT ANSWERS-d. defective evaporator
To prevent reliquefaction of sulfur dioxide gas in a conducting pipe, what should the temperature range
of the room be?
a. 60 to 80°F b. 70 to 85°F c. 80 to 90°F d. 90 to 100°F - CORRECT ANSWERS-c. 80 to 90°F
If the floc is too small in the solids removal physical-chemical treatment process, what is the most
probable cause?
a. paddle speed of flocculators too slow b. not enough dilution water c. improper or misaligned baffling
d. change in pH - CORRECT ANSWERS-d. change in pH
If the floc is too small in the solids removal physical-chemical treatment process, what is the most
plausible solution?
a. increase paddle speed of first flocculator b. add a coagulant aid c. check dosage with jar test d.
increase detention time by pumping out sludge - CORRECT ANSWERS-c. check dosage with jar test
If the floc is too large and thus settles too soon in the solids removal physical-chemical treatment
process, what is the most probable cause?
a. too much dilution water b. chemical makeup is too strong c. excessive addition of coagulant aid d.
cross-collectors not functioning - CORRECT ANSWERS-b. chemical makeup is too strong
