, Question 1
A water system experiences a sudden drop in distribution pressure to 15 psi in
a residential area. The operator suspects a major main break. Which of the
following actions is the most appropriate immediate response?
A. Increase pump discharge pressure to compensate for the loss.
B. Isolate the affected area by closing valves to contain the break and
notify the public.
C. Flush hydrants in the area to restore pressure.
D. Do nothing; pressure will stabilize once the break is repaired.
Correct Answer: B - Isolate the affected area by closing valves to
contain the break and notify the public.
RATIONALE
Isolating the break prevents further water loss and contamination, and
public notification is required for potential health risks. Increasing
pump pressure could worsen the break, flushing hydrants would lower
pressure further, and doing nothing ignores regulatory and safety
obligations.
Question 2
In a conventional surface water treatment plant, a rapid mix unit is followed by
flocculation and sedimentation. If the raw water has high alkalinity and low
turbidity, which coagulant adjustment is most likely to improve particle
removal?
A. Switch from alum to ferric chloride and increase dose.
B. Decrease coagulant dose and raise pH.
C. Add a polymer as a primary coagulant instead of metal salt.
D. Increase coagulant dose and consider acid addition to lower pH.
Correct Answer: D - Increase coagulant dose and consider acid
addition to lower pH.
Page 2
, RATIONALE
High alkalinity resists pH change, so more coagulant is needed to
achieve the optimal pH range for coagulation; acid may be required to
lower pH. Switching coagulants or reducing dose would not overcome
the alkalinity buffer, and polymers alone are less effective for charge
neutralization.
Question 3
A groundwater system using chlorine disinfection must maintain a minimum
residual of 0.2 mg/L in the distribution system. If a storage tank has a chlorine
demand of 1.5 mg/L and the desired residual is 0.5 mg/L, what initial chlorine
dose (mg/L) is required?
A. 1.5 mg/L
B. 2.0 mg/L
C. 2.5 mg/L
D. 0.7 mg/L
Correct Answer: B - 2.0 mg/L
RATIONALE
The required dose equals demand plus desired residual: 1.5 + 0.5 = 2.0
mg/L. Other options incorrectly add or omit the demand or residual.
Question 4
Which of the following best describes the purpose of a clear well in a surface
water treatment plant?
A. To provide contact time for disinfection and storage for filter
backwashing.
B. To remove dissolved gases and volatile organic compounds.
C. To act as a sedimentation basin for floc removal.
D. To adjust pH before coagulation.
Correct Answer: A - To provide contact time for disinfection and
Page 3
, storage for filter backwashing.
RATIONALE
Clear wells store treated water and provide chlorine contact time (CT)
for disinfection, as well as supply water for backwashing filters. They
do not primarily remove gases, act as sedimentation basins, or adjust
pH.
Question 5
A water system is required to monitor for lead and copper under the Lead and
Copper Rule. If the 90th percentile lead level is 0.018 mg/L, what is the next
required action?
A. No action; the level is below the action level.
B. Public notification and corrosion control treatment evaluation.
C. Immediate replacement of all lead service lines.
D. Increase monitoring frequency to quarterly.
Correct Answer: B - Public notification and corrosion control
treatment evaluation.
RATIONALE
The lead action level is 0.015 mg/L; exceeding it triggers public
education, corrosion control studies, and possible source water
treatment. Immediate line replacement is not required, and monitoring
frequency changes are not the first step.
Question 6
In a distribution system, a pump is operating at 100 ft head and 500 gpm. If the
pump speed is increased by 20%, what is the approximate new flow rate,
assuming affinity laws apply?
A. 600 gpm
B. 720 gpm
C. 500 gpm
Page 4
A water system experiences a sudden drop in distribution pressure to 15 psi in
a residential area. The operator suspects a major main break. Which of the
following actions is the most appropriate immediate response?
A. Increase pump discharge pressure to compensate for the loss.
B. Isolate the affected area by closing valves to contain the break and
notify the public.
C. Flush hydrants in the area to restore pressure.
D. Do nothing; pressure will stabilize once the break is repaired.
Correct Answer: B - Isolate the affected area by closing valves to
contain the break and notify the public.
RATIONALE
Isolating the break prevents further water loss and contamination, and
public notification is required for potential health risks. Increasing
pump pressure could worsen the break, flushing hydrants would lower
pressure further, and doing nothing ignores regulatory and safety
obligations.
Question 2
In a conventional surface water treatment plant, a rapid mix unit is followed by
flocculation and sedimentation. If the raw water has high alkalinity and low
turbidity, which coagulant adjustment is most likely to improve particle
removal?
A. Switch from alum to ferric chloride and increase dose.
B. Decrease coagulant dose and raise pH.
C. Add a polymer as a primary coagulant instead of metal salt.
D. Increase coagulant dose and consider acid addition to lower pH.
Correct Answer: D - Increase coagulant dose and consider acid
addition to lower pH.
Page 2
, RATIONALE
High alkalinity resists pH change, so more coagulant is needed to
achieve the optimal pH range for coagulation; acid may be required to
lower pH. Switching coagulants or reducing dose would not overcome
the alkalinity buffer, and polymers alone are less effective for charge
neutralization.
Question 3
A groundwater system using chlorine disinfection must maintain a minimum
residual of 0.2 mg/L in the distribution system. If a storage tank has a chlorine
demand of 1.5 mg/L and the desired residual is 0.5 mg/L, what initial chlorine
dose (mg/L) is required?
A. 1.5 mg/L
B. 2.0 mg/L
C. 2.5 mg/L
D. 0.7 mg/L
Correct Answer: B - 2.0 mg/L
RATIONALE
The required dose equals demand plus desired residual: 1.5 + 0.5 = 2.0
mg/L. Other options incorrectly add or omit the demand or residual.
Question 4
Which of the following best describes the purpose of a clear well in a surface
water treatment plant?
A. To provide contact time for disinfection and storage for filter
backwashing.
B. To remove dissolved gases and volatile organic compounds.
C. To act as a sedimentation basin for floc removal.
D. To adjust pH before coagulation.
Correct Answer: A - To provide contact time for disinfection and
Page 3
, storage for filter backwashing.
RATIONALE
Clear wells store treated water and provide chlorine contact time (CT)
for disinfection, as well as supply water for backwashing filters. They
do not primarily remove gases, act as sedimentation basins, or adjust
pH.
Question 5
A water system is required to monitor for lead and copper under the Lead and
Copper Rule. If the 90th percentile lead level is 0.018 mg/L, what is the next
required action?
A. No action; the level is below the action level.
B. Public notification and corrosion control treatment evaluation.
C. Immediate replacement of all lead service lines.
D. Increase monitoring frequency to quarterly.
Correct Answer: B - Public notification and corrosion control
treatment evaluation.
RATIONALE
The lead action level is 0.015 mg/L; exceeding it triggers public
education, corrosion control studies, and possible source water
treatment. Immediate line replacement is not required, and monitoring
frequency changes are not the first step.
Question 6
In a distribution system, a pump is operating at 100 ft head and 500 gpm. If the
pump speed is increased by 20%, what is the approximate new flow rate,
assuming affinity laws apply?
A. 600 gpm
B. 720 gpm
C. 500 gpm
Page 4
