(Part 1) Grade 4 Wastewater Certification Practice Test Exam with Questions and
Answers – 100% Solved
. At what level should the alkalinity level be maintained in a rotating biological contactor
wastewater plant when nitrification is occurring?
a. 3.4 times the influent ammonia b. 4.2 times the influent ammonia c. 5.8 times the influent
ammonia d. 7.1 times the influent ammonia - ✔✔✔-d. 7.1 times the influent ammonia
. What is the beneficial concentration range of ammonia nitrogen in an anaerobic digester?
a. 50 to 150 mg/L b. 50 to 200 mg/L c. 75 to 225 mg/L d. 100 to 250 mg/L - ✔✔✔-b. 50 to 200
mg/L
2. What is the 5-day sludge age equivalent to?
a. 1 lb of food per 5 lb of organisms b. 1 lb of organisms per 5 lb of food c. 5 days of BOD d. 5
days by weight of mixed liquor suspended solids - ✔✔✔-a. 1 lb of food per 5 lb of organisms
A high pH in a waste treatment pond will balance
a. aerobic fermentation b. anaerobic fermentation c. CO2 and O2 production by algae and
other microorganisms d. algae and bacterial communities - ✔✔✔-b. anaerobic fermentation
A modified version of the activated sludge process for removing phosphorus and nitrogen
would have the following sequence of tank environments:
a. anaerobic, anoxic, and aerobic b. aerobic, nitrification, and anaerobic c. anaerobic, anoxic,
and denitrification d. anaerobic, nitrification, aerobic, and denitrification - ✔✔✔-a. anaerobic,
anoxic, and aerobic
,(Part 1) Grade 4 Wastewater Certification Practice Test Exam with Questions and
Answers – 100% Solved
A settleability test is performed on a secondary clarifier at an activated sludge plant. If the
sludge floats too soon, then the sludge age should be reduced. What else may be done?
a. increase the DO b. decrease the BOD c. increase the F/M (food-to-microorganism) ratio d.
decrease the F/M ratio - ✔✔✔-c. increase the F/M (food-to-microorganism) ratio
A shock load of toxic wastes coming into a plant can be treated or controlled with
a. coagulants only b. coagulants and lime c. coagulants and coagulant aid d. coagulants or
chlorine - ✔✔✔-d. coagulants or chlorine
A significant temperature change for an activated sludge plant is usually plus or minus
a. 4°F b. 5°F c. 7°F d. 10°F - ✔✔✔-d. 10°F
A thick dark foam on the surface of the oxidation ditch indicates that the
a. process is performing well b. rotor revolutions per minute (rpm) are too fast c. wasting rate
should be increased d. flow through the ditch is too slow - ✔✔✔-c. wasting rate should be
increased
A waste pond that is overloaded will usually be
a. light green b. dull green c. grayish green d. gray - ✔✔✔-d. gray
Adequate amounts of nitrogen and phosphorous are especially lacking most often from which
one of the following wastes?
, (Part 1) Grade 4 Wastewater Certification Practice Test Exam with Questions and
Answers – 100% Solved
a. industrial b. domestic c. fermentation industries d. food processing - ✔✔✔-d. food
processing
All occupied trenches 4 or more ft deep must provide exits at a. 15-ft intervals b. 20-ft intervals
c. 25-ft intervals d. 30-ft intervals - ✔✔✔-c. 25-ft intervals
An activated sludge plant has wastewater with a temperature of 20°C. In general, in days, what
MCRT is needed for the plant to produce a nitrified effluent?
a. 10 days b. 15 days c. 20 days d. 30 days - ✔✔✔-b. 15 days
An operator starting up a new sequencing batch reactor plant obtains 2,000 gal of seed sludge
from another activated sludge plant. How long will it take before this seed sludge is capable of
treating wastewater?
a. 3 to 5 days b. 1 to 2 weeks c. 1 month d. 2 months - ✔✔✔-b. 1 to 2 weeks
An operator working at a waste treatment pond knows that a surface aerator is working
properly when
a. no foam is on the surface b. very little foam is on the surface c. some scum and foam is on the
surface d. very little foam is on the surface so aeration time is backed off 10% - ✔✔✔-b. very
little foam is on the surface
At what pH will sodium hydroxide control sulfide generation for periods of about a month or
more?
a. 9.5 b. 10.5 c. 11.5 d. 12.5 - ✔✔✔-d. 12.5
Answers – 100% Solved
. At what level should the alkalinity level be maintained in a rotating biological contactor
wastewater plant when nitrification is occurring?
a. 3.4 times the influent ammonia b. 4.2 times the influent ammonia c. 5.8 times the influent
ammonia d. 7.1 times the influent ammonia - ✔✔✔-d. 7.1 times the influent ammonia
. What is the beneficial concentration range of ammonia nitrogen in an anaerobic digester?
a. 50 to 150 mg/L b. 50 to 200 mg/L c. 75 to 225 mg/L d. 100 to 250 mg/L - ✔✔✔-b. 50 to 200
mg/L
2. What is the 5-day sludge age equivalent to?
a. 1 lb of food per 5 lb of organisms b. 1 lb of organisms per 5 lb of food c. 5 days of BOD d. 5
days by weight of mixed liquor suspended solids - ✔✔✔-a. 1 lb of food per 5 lb of organisms
A high pH in a waste treatment pond will balance
a. aerobic fermentation b. anaerobic fermentation c. CO2 and O2 production by algae and
other microorganisms d. algae and bacterial communities - ✔✔✔-b. anaerobic fermentation
A modified version of the activated sludge process for removing phosphorus and nitrogen
would have the following sequence of tank environments:
a. anaerobic, anoxic, and aerobic b. aerobic, nitrification, and anaerobic c. anaerobic, anoxic,
and denitrification d. anaerobic, nitrification, aerobic, and denitrification - ✔✔✔-a. anaerobic,
anoxic, and aerobic
,(Part 1) Grade 4 Wastewater Certification Practice Test Exam with Questions and
Answers – 100% Solved
A settleability test is performed on a secondary clarifier at an activated sludge plant. If the
sludge floats too soon, then the sludge age should be reduced. What else may be done?
a. increase the DO b. decrease the BOD c. increase the F/M (food-to-microorganism) ratio d.
decrease the F/M ratio - ✔✔✔-c. increase the F/M (food-to-microorganism) ratio
A shock load of toxic wastes coming into a plant can be treated or controlled with
a. coagulants only b. coagulants and lime c. coagulants and coagulant aid d. coagulants or
chlorine - ✔✔✔-d. coagulants or chlorine
A significant temperature change for an activated sludge plant is usually plus or minus
a. 4°F b. 5°F c. 7°F d. 10°F - ✔✔✔-d. 10°F
A thick dark foam on the surface of the oxidation ditch indicates that the
a. process is performing well b. rotor revolutions per minute (rpm) are too fast c. wasting rate
should be increased d. flow through the ditch is too slow - ✔✔✔-c. wasting rate should be
increased
A waste pond that is overloaded will usually be
a. light green b. dull green c. grayish green d. gray - ✔✔✔-d. gray
Adequate amounts of nitrogen and phosphorous are especially lacking most often from which
one of the following wastes?
, (Part 1) Grade 4 Wastewater Certification Practice Test Exam with Questions and
Answers – 100% Solved
a. industrial b. domestic c. fermentation industries d. food processing - ✔✔✔-d. food
processing
All occupied trenches 4 or more ft deep must provide exits at a. 15-ft intervals b. 20-ft intervals
c. 25-ft intervals d. 30-ft intervals - ✔✔✔-c. 25-ft intervals
An activated sludge plant has wastewater with a temperature of 20°C. In general, in days, what
MCRT is needed for the plant to produce a nitrified effluent?
a. 10 days b. 15 days c. 20 days d. 30 days - ✔✔✔-b. 15 days
An operator starting up a new sequencing batch reactor plant obtains 2,000 gal of seed sludge
from another activated sludge plant. How long will it take before this seed sludge is capable of
treating wastewater?
a. 3 to 5 days b. 1 to 2 weeks c. 1 month d. 2 months - ✔✔✔-b. 1 to 2 weeks
An operator working at a waste treatment pond knows that a surface aerator is working
properly when
a. no foam is on the surface b. very little foam is on the surface c. some scum and foam is on the
surface d. very little foam is on the surface so aeration time is backed off 10% - ✔✔✔-b. very
little foam is on the surface
At what pH will sodium hydroxide control sulfide generation for periods of about a month or
more?
a. 9.5 b. 10.5 c. 11.5 d. 12.5 - ✔✔✔-d. 12.5
