GRADE 4 WASTEWATER CERTIFICATION
EXAM 2026/2027 WITH QUESTIONS AND
CORRECT ANSWERS | ALREADY GRADED
A+ | GUARANTEED PASS | WASTEWATER
LATEST EXAM
During the startup of the oxidation sludge process in the oxidation ditch, the operator
should maintain the highest
a. recommended level of dissolved oxygen b. inflow of raw wastewater possible in order
to fill the ditch c. possible rate of returned activated sludge d. possible brush rotor speed
advisable - ✅🌹CORRECT ANSWER-c. possible rate of returned activated sludge
What is the best range of dissolved oxygen in an oxidation ditch for optimum operation?
a. 0.5 to 2.0 mg/L b. 1.0 to 2.0 mg/L c. 1.0 to 2.5 mg/L d. 1.0 to 3.0 mg/L -
✅🌹CORRECT ANSWER-a. 0.5 to 2.0 mg/L
Overoxidation of an oxidation ditch will cause
a. an algae bloom b. suspended solids to float c. oxygen toxicity for protozoans and
other organisms, especially rotifers d. the formation of pinpoint floc - ✅🌹CORRECT
ANSWER-d. the formation of pinpoint floc
In the oxidation ditch process, what should be done if dark solids appear in the settling
tank?
a. increase disinfection to reduce septic conditions and waste b. increase the return
sludge rate c. add oxygen to the settling tank through the clarifier's diffusers d. waste all
the solids and start the settling process over - ✅🌹CORRECT ANSWER-b. increase the
return sludge rate
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 - ✅🌹CORRECT
ANSWER-c. wasting rate should be increased
What should the operator do if the oxidation ditch becomes hydraulically overloaded
due to a heavy rainstorm?
a. temporarily store the excess rainwater in the primary clarifier b. increase the
dissolved oxygen levels c. shut down one or more rotor assemblies d. send excess
wastewater to the settling tank - ✅🌹CORRECT ANSWER-c. shut down one or more
rotor assemblies
The blower system at a wastewater plant has to be shut off for cleaning the activated
sludge process. The process will not be adversely affected, if the system is off for only
a. 5 to 10 min b. 15 to 30 min c. 30 to 60 min d. 1 to 2 hr - ✅🌹CORRECT ANSWER-c.
30 to 60 min
When the pressure difference indicated on a manometer reads _______, the air filters
on a blower for an aeration tank should be cleaned or changed.
a. 3 in. b. 5 in. c. 7 in. d. 10 in. - ✅🌹CORRECT ANSWER-a. 3 in.
The waste activated sludge wasting rate should not be changed by more than _______
from one day to the next.
a. 10 to 15% b. 20% c. 20 to 25% d. 25% - ✅🌹CORRECT ANSWER-a. 10 to 15%
What is the possible number of pounds of sludge volatile matter produced per pound of
biochemical oxygen demand (BOD) removed from a conventional plant running the
activated sludge process?
a. 0.15 lb b. 0.25 lb c. 0.55 lb d. 0.85 lb - ✅🌹CORRECT ANSWER-c. 0.55 lb
If an operator calculates the wasting rate for activated sludge to be 45 gpm over the
following 24 hr, the operator should waste
a. the theoretical wasting rate calculated (45 gpm) b. a little less than the theoretical
wasting rate c. a little more than the theoretical wasting rate d. at least 15% more, since
the amount of activated sludge will increase by about that much over the next 24 hr -
✅🌹CORRECT ANSWER-b. a little less than the theoretical wasting rate
EXAM 2026/2027 WITH QUESTIONS AND
CORRECT ANSWERS | ALREADY GRADED
A+ | GUARANTEED PASS | WASTEWATER
LATEST EXAM
During the startup of the oxidation sludge process in the oxidation ditch, the operator
should maintain the highest
a. recommended level of dissolved oxygen b. inflow of raw wastewater possible in order
to fill the ditch c. possible rate of returned activated sludge d. possible brush rotor speed
advisable - ✅🌹CORRECT ANSWER-c. possible rate of returned activated sludge
What is the best range of dissolved oxygen in an oxidation ditch for optimum operation?
a. 0.5 to 2.0 mg/L b. 1.0 to 2.0 mg/L c. 1.0 to 2.5 mg/L d. 1.0 to 3.0 mg/L -
✅🌹CORRECT ANSWER-a. 0.5 to 2.0 mg/L
Overoxidation of an oxidation ditch will cause
a. an algae bloom b. suspended solids to float c. oxygen toxicity for protozoans and
other organisms, especially rotifers d. the formation of pinpoint floc - ✅🌹CORRECT
ANSWER-d. the formation of pinpoint floc
In the oxidation ditch process, what should be done if dark solids appear in the settling
tank?
a. increase disinfection to reduce septic conditions and waste b. increase the return
sludge rate c. add oxygen to the settling tank through the clarifier's diffusers d. waste all
the solids and start the settling process over - ✅🌹CORRECT ANSWER-b. increase the
return sludge rate
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 - ✅🌹CORRECT
ANSWER-c. wasting rate should be increased
What should the operator do if the oxidation ditch becomes hydraulically overloaded
due to a heavy rainstorm?
a. temporarily store the excess rainwater in the primary clarifier b. increase the
dissolved oxygen levels c. shut down one or more rotor assemblies d. send excess
wastewater to the settling tank - ✅🌹CORRECT ANSWER-c. shut down one or more
rotor assemblies
The blower system at a wastewater plant has to be shut off for cleaning the activated
sludge process. The process will not be adversely affected, if the system is off for only
a. 5 to 10 min b. 15 to 30 min c. 30 to 60 min d. 1 to 2 hr - ✅🌹CORRECT ANSWER-c.
30 to 60 min
When the pressure difference indicated on a manometer reads _______, the air filters
on a blower for an aeration tank should be cleaned or changed.
a. 3 in. b. 5 in. c. 7 in. d. 10 in. - ✅🌹CORRECT ANSWER-a. 3 in.
The waste activated sludge wasting rate should not be changed by more than _______
from one day to the next.
a. 10 to 15% b. 20% c. 20 to 25% d. 25% - ✅🌹CORRECT ANSWER-a. 10 to 15%
What is the possible number of pounds of sludge volatile matter produced per pound of
biochemical oxygen demand (BOD) removed from a conventional plant running the
activated sludge process?
a. 0.15 lb b. 0.25 lb c. 0.55 lb d. 0.85 lb - ✅🌹CORRECT ANSWER-c. 0.55 lb
If an operator calculates the wasting rate for activated sludge to be 45 gpm over the
following 24 hr, the operator should waste
a. the theoretical wasting rate calculated (45 gpm) b. a little less than the theoretical
wasting rate c. a little more than the theoretical wasting rate d. at least 15% more, since
the amount of activated sludge will increase by about that much over the next 24 hr -
✅🌹CORRECT ANSWER-b. a little less than the theoretical wasting rate
