CWEA (Part 1) Grade 4 wastewater cer fica on prac ce
test With complete solu on Rated A+ 2025/2026 NEW!!
What is the odor detec on limit of chlorine gas?
a. 0.1 ppm b. 0.3 ppm c. 0.5 ppm d. 1.0 ppm - Ans b. 0.3 ppm
What is a cathode?
a. nega ve pole of an electrolyte b. posi ve pole of an electrolyte c. nega ve pole of an
electroly c cell or system d. posi ve pole of an electroly c cell or system - Ans nega ve pole of
an electroly c cell or system
The least reac ve metals are called a. anodic metals b. galvanic metals c. cathodic metals d.
tempered metals - Ans c. cathodic metals
Unless water cooled, the opera ng temperature of a mechanical seal in a pump should never
exceed a. 95°F (35°C) b. 120°F (49°C) c. 140°F (60°C) d. 160°F (71°C) - Ans d. 160°F (71°C)
What term describes the condi on that exists when the source of the water supply is below the
centerline of the pump? a. total discharge head b. suc on li/ c. velocity head d. pressure head -
Ans b. suc on li/
All occupied trenches 4 or more / deep must provide exits at a. 15-/ intervals b. 20-/ intervals
c. 25-/ intervals d. 30-/ intervals - Ans c. 25-/ intervals
What is the difference between a weak acid and a strong acid? a. amount of buffering released
b. amount of hydroxyl ions released c. amount of carbonate ions released d. amount of
hydrogen ions released - Ans d. amount of hydrogen ions released
,Which one of the following is the best type of valve to use to dampen a water hammer? a.
needle b. pressure-relief c. pressure-reducing d. pinch - Ans b. pressure-relief
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 - Ans d. coagulants or chlorine
Toxic solids should be disposed of in
a. a digester to destabilize and break down the toxins b. an approved sanitary landfill c. an
incinerator d. a sludge pond for further aerobic breakdown - Ans b. an approved sanitary landfill
Which one of the following best defines the term stray-current corrosion?
a. decomposi on of a metal by its reac on with an acidic water b. decomposi on of a material
caused by an outside electric current c. reac on between a metal and water d. reac on
between two different metals with water ac ng as an electrolyte - Ans b. decomposi on of a
material caused by an outside electric current
On startup of a small package wastewater treatment plant, lime should be added to the
diges on unit when the pH goes below
a. 6.8 b. 7.0 c. 7.2 d. 7.5 - Ans b. 7.0
If the effluent to a small package wastewater treatment plant using the ac vated sludge
process appears turbid, what is most probably the cause?
, a. low concentra on of dissolved oxygen (DO) in the aera on tank b. pumping rate for the
return of ac vated sludge is out of balance c. excessive aera on rates in the aera on tank d.
alkalinity is too high - Ans b. pumping rate for the return of ac vated sludge is out of balance
If a small package treatment plant u lizing the ac vated sludge process has a lightcolored
floa ng sludge on the surface of the clarifier, which one of the following would most likely
eliminate the floa ng sludge?
a. increase the sludge was ng rate b. add a pH stabilizer, as pH is too low c. reduce the aera on
rates d. increase the return sludge rate - Ans c. reduce the aera on rates
What usually causes frothing in the ac vated sludge process?
a. too low a solids level b. too high a solids leaving c. too short a reten on me d. too long a
deten on me - Ans d. too long a deten on me
Which one of the following sugges ons would most likely control foaming?
a. increase the deten on me b. water sprays c. increase the dissolved oxygen d. increase
solids was ng - Ans b. water sprays
What is the ideal level of solids in a jar test sample collected from an aera on tank if it is
allowed to se<le for 30 min?
a. ¼ of the jar depth b. ⅓ of the jar depth c. ⅖ of the jar depth d. ½ of the jar depth - Ans d. ½ of
the jar depth
In a small wastewater treatment plant using the ac vated sludge process, solids in the se<ling
compartment should not be allowed to remain longer than
test With complete solu on Rated A+ 2025/2026 NEW!!
What is the odor detec on limit of chlorine gas?
a. 0.1 ppm b. 0.3 ppm c. 0.5 ppm d. 1.0 ppm - Ans b. 0.3 ppm
What is a cathode?
a. nega ve pole of an electrolyte b. posi ve pole of an electrolyte c. nega ve pole of an
electroly c cell or system d. posi ve pole of an electroly c cell or system - Ans nega ve pole of
an electroly c cell or system
The least reac ve metals are called a. anodic metals b. galvanic metals c. cathodic metals d.
tempered metals - Ans c. cathodic metals
Unless water cooled, the opera ng temperature of a mechanical seal in a pump should never
exceed a. 95°F (35°C) b. 120°F (49°C) c. 140°F (60°C) d. 160°F (71°C) - Ans d. 160°F (71°C)
What term describes the condi on that exists when the source of the water supply is below the
centerline of the pump? a. total discharge head b. suc on li/ c. velocity head d. pressure head -
Ans b. suc on li/
All occupied trenches 4 or more / deep must provide exits at a. 15-/ intervals b. 20-/ intervals
c. 25-/ intervals d. 30-/ intervals - Ans c. 25-/ intervals
What is the difference between a weak acid and a strong acid? a. amount of buffering released
b. amount of hydroxyl ions released c. amount of carbonate ions released d. amount of
hydrogen ions released - Ans d. amount of hydrogen ions released
,Which one of the following is the best type of valve to use to dampen a water hammer? a.
needle b. pressure-relief c. pressure-reducing d. pinch - Ans b. pressure-relief
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 - Ans d. coagulants or chlorine
Toxic solids should be disposed of in
a. a digester to destabilize and break down the toxins b. an approved sanitary landfill c. an
incinerator d. a sludge pond for further aerobic breakdown - Ans b. an approved sanitary landfill
Which one of the following best defines the term stray-current corrosion?
a. decomposi on of a metal by its reac on with an acidic water b. decomposi on of a material
caused by an outside electric current c. reac on between a metal and water d. reac on
between two different metals with water ac ng as an electrolyte - Ans b. decomposi on of a
material caused by an outside electric current
On startup of a small package wastewater treatment plant, lime should be added to the
diges on unit when the pH goes below
a. 6.8 b. 7.0 c. 7.2 d. 7.5 - Ans b. 7.0
If the effluent to a small package wastewater treatment plant using the ac vated sludge
process appears turbid, what is most probably the cause?
, a. low concentra on of dissolved oxygen (DO) in the aera on tank b. pumping rate for the
return of ac vated sludge is out of balance c. excessive aera on rates in the aera on tank d.
alkalinity is too high - Ans b. pumping rate for the return of ac vated sludge is out of balance
If a small package treatment plant u lizing the ac vated sludge process has a lightcolored
floa ng sludge on the surface of the clarifier, which one of the following would most likely
eliminate the floa ng sludge?
a. increase the sludge was ng rate b. add a pH stabilizer, as pH is too low c. reduce the aera on
rates d. increase the return sludge rate - Ans c. reduce the aera on rates
What usually causes frothing in the ac vated sludge process?
a. too low a solids level b. too high a solids leaving c. too short a reten on me d. too long a
deten on me - Ans d. too long a deten on me
Which one of the following sugges ons would most likely control foaming?
a. increase the deten on me b. water sprays c. increase the dissolved oxygen d. increase
solids was ng - Ans b. water sprays
What is the ideal level of solids in a jar test sample collected from an aera on tank if it is
allowed to se<le for 30 min?
a. ¼ of the jar depth b. ⅓ of the jar depth c. ⅖ of the jar depth d. ½ of the jar depth - Ans d. ½ of
the jar depth
In a small wastewater treatment plant using the ac vated sludge process, solids in the se<ling
compartment should not be allowed to remain longer than
