CWEA (Part 1) Grade 4 Wastewater
Certification Practice Test
Questions and correct answers
1. What is the odor detection limit of chlorine gas?
a. 0.1 ppm
b. 0.3 ppm (Correct)
c. 0.5 ppm
d. 1.0 ppm
Explanation: The odor detection threshold for chlorine gas is
approximately 0.3 ppm, meaning most people can smell it at this
concentration.
2. What is a cathode?
a. Negative pole of an electrolyte
b. Positive pole of an electrolyte
c. Negative pole of an electrolytic cell or system
d. Positive pole of an electrolytic cell or system
Correct answer: c. negative pole of an electrolytic cell or system
Explanation: The cathode is the electrode where reduction occurs, and
in electrolytic cells, it is the negative electrode.
3. The least reactive metals are called:
a. Anodic metals
b. Galvanic metals
c. Cathodic metals (Correct)
,d. Tempered metals
Explanation: Cathodic metals are less reactive and less likely to corrode;
they tend to act as cathodes in galvanic cells.
4. Unless water cooled, the operating 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) (Correct)
Explanation: Mechanical seals typically have maximum operating
temperatures around 160°F to prevent damage.
5. What term describes the condition that exists when the source of
the water supply is below the centerline of the pump?
a. Total discharge head
b. Suction lift (Correct)
c. Velocity head
d. Pressure head
Explanation: Suction lift refers to pumping water from a level below the
pump’s centerline.
6. All occupied trenches 4 or more ft deep must provide exits at:
a. 15-ft intervals
b. 20-ft intervals
c. 25-ft intervals (Correct)
d. 30-ft intervals
, Explanation: OSHA regulations require exits every 25 feet in trenches
over 4 feet deep.
7. 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 (Correct)
Explanation: Strong acids release more hydrogen ions, resulting in a
lower pH compared to weak acids.
8. Which one of the following is the best type of valve to use to
dampen a water hammer?
a. Needle
b. Pressure-relief (Correct)
c. Pressure-reducing
d. Pinch
Explanation: Pressure-relief valves help absorb sudden pressure surges
caused by water hammer.
9. 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 (Correct)
Certification Practice Test
Questions and correct answers
1. What is the odor detection limit of chlorine gas?
a. 0.1 ppm
b. 0.3 ppm (Correct)
c. 0.5 ppm
d. 1.0 ppm
Explanation: The odor detection threshold for chlorine gas is
approximately 0.3 ppm, meaning most people can smell it at this
concentration.
2. What is a cathode?
a. Negative pole of an electrolyte
b. Positive pole of an electrolyte
c. Negative pole of an electrolytic cell or system
d. Positive pole of an electrolytic cell or system
Correct answer: c. negative pole of an electrolytic cell or system
Explanation: The cathode is the electrode where reduction occurs, and
in electrolytic cells, it is the negative electrode.
3. The least reactive metals are called:
a. Anodic metals
b. Galvanic metals
c. Cathodic metals (Correct)
,d. Tempered metals
Explanation: Cathodic metals are less reactive and less likely to corrode;
they tend to act as cathodes in galvanic cells.
4. Unless water cooled, the operating 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) (Correct)
Explanation: Mechanical seals typically have maximum operating
temperatures around 160°F to prevent damage.
5. What term describes the condition that exists when the source of
the water supply is below the centerline of the pump?
a. Total discharge head
b. Suction lift (Correct)
c. Velocity head
d. Pressure head
Explanation: Suction lift refers to pumping water from a level below the
pump’s centerline.
6. All occupied trenches 4 or more ft deep must provide exits at:
a. 15-ft intervals
b. 20-ft intervals
c. 25-ft intervals (Correct)
d. 30-ft intervals
, Explanation: OSHA regulations require exits every 25 feet in trenches
over 4 feet deep.
7. 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 (Correct)
Explanation: Strong acids release more hydrogen ions, resulting in a
lower pH compared to weak acids.
8. Which one of the following is the best type of valve to use to
dampen a water hammer?
a. Needle
b. Pressure-relief (Correct)
c. Pressure-reducing
d. Pinch
Explanation: Pressure-relief valves help absorb sudden pressure surges
caused by water hammer.
9. 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 (Correct)
