WASTEWATER CERTIFICATION EXAMS TEST PAPER
2025/2026 ANSWERS AND QUESTIONS GRADED A+
✔✔What is the only reliable method of detecting hydrogen sulfide?
A) Sense of smell
B) Atmospheric monitoring
C) Color titration
D) Lab test - ✔✔B) Atmospheric monitoring (v.2 pg 271)
✔✔What is sludge age?
A) An expression of the average time that a microorganism will spend in the activated
sludge process, and calculated using total suspended solids removed from the process
B) A measure of food provided to bacteria in an aeration tank
C) The theoretical time required for water to pass through a tank at any given flowrate
D) A rough indicator of the length of time a pound of solids is maintained under aeration
- ✔✔D) A rough indicator of the length of time a pound of solids is maintained under
aeration (v.2 pg 519)
✔✔What is one of the benefits of a COD test over a BOD test?
A) COD test does not require any chemicals to perform the test
B) COD test will easily predict the effects of an effluent on the DO in receiving waters
C) Shorter test period
D) COD test is capable of measuring the biodegradability of matter - ✔✔C) Shorter test
period (v.2 pg 541)
✔✔What is the typical detention time for a primary clarifier?
A) 3 to 4 hours
B) 30 minutes
C) 6 hours
D) 1.5 to 2 hours - ✔✔D) 1.5 to 2 hours (v.1 pg 43)
✔✔If you are testing the pH of a wastewater sample, what is the maximum
recommended holding time?
A) 5 days
B) It must be tested immediately
C) 24 hours
D) 36 hours - ✔✔B) It must be tested immediately (v.2 pg 502)
✔✔What could cause short circuiting in a clarifier?
, A) Sludge composition
B) Reduction in flowrate
C) Uneven weir settings
D) Broken sludge pump - ✔✔C) Uneven weir settings (v.1 pg 125)
✔✔What could cause the slime growth on a rotating biological contactor to appear
black?
A) It could indicate solids or organic overloading
B) High DO in the plant effluent
C) Lack of BOD in the influent to the rotating biological contactor
D) Low hydraulic loading - ✔✔A) It could indicate solids or organic overloading (v.1 pg
228)
✔✔What is an air gap?
A) A distance between blowers in an activated sludge system
B) The vertical distance between the surface of wastewater and the top of basin
C) Backflow prevention
D) Type of aeration equipment - ✔✔C) Backflow prevention (v.1 pg 503)
✔✔Which is true about chlorine demand?
A) Chlorine demand= Chlorine residual + Chlorine dose
B) Chlorine demand= Chlorine does x Chlorine residual
C) Chlorine demand= Chlorine residual - Chlorine dose
D) Chlorine demand= Chlorine dose - Chlorine residual - ✔✔D) Chlorine demand=
Chlorine dose - Chlorine residual (v.1 pg 352)
✔✔What is accomplished by the activated sludge process?
A) Anaerobic bacteria use SO_4 to eat incoming volatile solids
B) Remove soluble or finely divided suspended materials
C) Anoxic microorganisms destroy incoming BOD
D) Zoogleal breaks down influent organics - ✔✔B) Remove soluble or finely divided
suspended materials (v.2 pg 16)
✔✔What is the carbon dioxide content of a properly functioning anaerobic digester?
A) 65 to 70% by volume
B) 1 to 2% by volume
C) 30 to 35% by volume
D) 40 to 60% by volume - ✔✔C) 30 to 35% by volume (v.2 pg 158)
2025/2026 ANSWERS AND QUESTIONS GRADED A+
✔✔What is the only reliable method of detecting hydrogen sulfide?
A) Sense of smell
B) Atmospheric monitoring
C) Color titration
D) Lab test - ✔✔B) Atmospheric monitoring (v.2 pg 271)
✔✔What is sludge age?
A) An expression of the average time that a microorganism will spend in the activated
sludge process, and calculated using total suspended solids removed from the process
B) A measure of food provided to bacteria in an aeration tank
C) The theoretical time required for water to pass through a tank at any given flowrate
D) A rough indicator of the length of time a pound of solids is maintained under aeration
- ✔✔D) A rough indicator of the length of time a pound of solids is maintained under
aeration (v.2 pg 519)
✔✔What is one of the benefits of a COD test over a BOD test?
A) COD test does not require any chemicals to perform the test
B) COD test will easily predict the effects of an effluent on the DO in receiving waters
C) Shorter test period
D) COD test is capable of measuring the biodegradability of matter - ✔✔C) Shorter test
period (v.2 pg 541)
✔✔What is the typical detention time for a primary clarifier?
A) 3 to 4 hours
B) 30 minutes
C) 6 hours
D) 1.5 to 2 hours - ✔✔D) 1.5 to 2 hours (v.1 pg 43)
✔✔If you are testing the pH of a wastewater sample, what is the maximum
recommended holding time?
A) 5 days
B) It must be tested immediately
C) 24 hours
D) 36 hours - ✔✔B) It must be tested immediately (v.2 pg 502)
✔✔What could cause short circuiting in a clarifier?
, A) Sludge composition
B) Reduction in flowrate
C) Uneven weir settings
D) Broken sludge pump - ✔✔C) Uneven weir settings (v.1 pg 125)
✔✔What could cause the slime growth on a rotating biological contactor to appear
black?
A) It could indicate solids or organic overloading
B) High DO in the plant effluent
C) Lack of BOD in the influent to the rotating biological contactor
D) Low hydraulic loading - ✔✔A) It could indicate solids or organic overloading (v.1 pg
228)
✔✔What is an air gap?
A) A distance between blowers in an activated sludge system
B) The vertical distance between the surface of wastewater and the top of basin
C) Backflow prevention
D) Type of aeration equipment - ✔✔C) Backflow prevention (v.1 pg 503)
✔✔Which is true about chlorine demand?
A) Chlorine demand= Chlorine residual + Chlorine dose
B) Chlorine demand= Chlorine does x Chlorine residual
C) Chlorine demand= Chlorine residual - Chlorine dose
D) Chlorine demand= Chlorine dose - Chlorine residual - ✔✔D) Chlorine demand=
Chlorine dose - Chlorine residual (v.1 pg 352)
✔✔What is accomplished by the activated sludge process?
A) Anaerobic bacteria use SO_4 to eat incoming volatile solids
B) Remove soluble or finely divided suspended materials
C) Anoxic microorganisms destroy incoming BOD
D) Zoogleal breaks down influent organics - ✔✔B) Remove soluble or finely divided
suspended materials (v.2 pg 16)
✔✔What is the carbon dioxide content of a properly functioning anaerobic digester?
A) 65 to 70% by volume
B) 1 to 2% by volume
C) 30 to 35% by volume
D) 40 to 60% by volume - ✔✔C) 30 to 35% by volume (v.2 pg 158)
