MARYLAND WATER TREATMENT
PLANT OPERATOR CLASS 1 -5
CERTIFICATION EXAM
QUESTIONS AND VERIFIED
MARYLAND WATER TREATMENT PLANT OPERATOR CLASS
1 | Comprehensive Examination
MARYLAND WATER TREATMENT PLANT OPERATOR
CLASS 1 -5 CERTIFICATION EXAM QUESTIONS AND
VERIFIED ANSWERS.pdf actual exam preparation
INTRODUCTION
This document is an important and very helpful preparation
resource for MARYLAND WATER TREATMENT PLANT
OPERATOR CLASS 1 -5 CERTIFICATION EXAM
QUESTIONS AND VERIFIED ANSWERS.pdf. Every item
uses a focused exam stem, four response options, a keyed
response, and a clear rationale, making it easier to understand
the subject, spot distractors, and build real exam confidence.
Page 1
, Question 1
A surface water plant using alum coagulation experiences a sudden drop in raw
water alkalinity from 120 mg/L to 25 mg/L as CaCO3. Jar tests show optimal
alum dose at 40 mg/L but floc formation is poor and pH drops to 5.2. What is
the most appropriate operational adjustment?
A. Increase alum dose to 60 mg/L to compensate for reduced alkalinity
B. Add sodium hydroxide or soda ash to raise alkalinity and maintain pH
near 6.5-7.0
C. Switch to a non-ionic polymer as the primary coagulant
D. Reduce alum dose to 20 mg/L and increase flocculation time
Correct Answer: B - Add sodium hydroxide or soda ash to raise
alkalinity and maintain pH near 6.5-7.0
RATIONALE
Alum consumes alkalinity and lowers pH; at 25 mg/L alkalinity,
insufficient buffering causes pH to fall below the optimal coagulation
range. Adding alkali restores alkalinity and pH, improving floc
formation. Increasing alum worsens the problem, and non-ionic
polymers are not primary coagulants.
Question 2
A conventional filter with a surface area of 100 ft² operates at a filtration rate
of 4 gpm/ft². If the filter run is 30 hours, what is the total volume of water
filtered in gallons?
A. 720,000 gallons
B. 1,200,000 gallons
C. 12,000 gallons
D. 72,000 gallons
Correct Answer: A - 720,000 gallons
Page 2
, RATIONALE
Flow = 4 gpm/ft² × 100 ft² = 400 gpm. Over 30 hours = 400 × 60 × 30
= 720,000 gallons. Other options reflect arithmetic errors in unit
conversion or multiplication.
Question 3
A distribution system sample shows a chlorine residual of 0.2 mg/L free
chlorine at a dead-end main, while the treatment plant effluent has 1.0 mg/L.
What is the most likely cause?
A. Excessive chlorine demand from nitrification or biofilm in the
dead-end main
B. Chlorine decay due to high pH in the distribution system
C. Sample error from using a DPD colorimeter
D. Reduction of chlorine by fluoride addition at the plant
Correct Answer: A - Excessive chlorine demand from
nitrification or biofilm in the dead-end main
RATIONALE
Dead-end mains often experience stagnation, biofilm growth, and
nitrification, which consume free chlorine. A drop from 1.0 to 0.2
mg/L suggests significant demand. High pH would slow decay, not
accelerate it, and fluoride does not reduce chlorine.
Question 4
In a CT calculation for Giardia inactivation, if the disinfectant residual is 1.5
mg/L, the contact time is 20 minutes, and the peak hourly flow is 2.0 MGD,
what is the CT value (mg-min/L) assuming a baffling factor of 0.7?
A. 21 mg-min/L
B. 30 mg-min/L
C. 10.5 mg-min/L
D. 42 mg-min/L
Page 3
, Correct Answer: A - 21 mg-min/L
RATIONALE
CT = residual × effective contact time. Effective time = 20 min × 0.7 =
14 min. CT = 1.5 × 14 = 21 mg-min/L. Other options reflect omission
of baffling factor or incorrect multiplication.
Question 5
A plant using ozone for primary disinfection observes a sudden increase in
bromate formation in treated water. Which operational change is most effective
in reducing bromate while maintaining disinfection?
A. Increase ozone dose and contact time
B. Lower pH and reduce ozone dose, or switch to chloramine as
secondary disinfectant
C. Add ammonia upstream of ozone to form chloramines
D. Increase bromide removal by adding more coagulant
Correct Answer: B - Lower pH and reduce ozone dose, or switch
to chloramine as secondary disinfectant
RATIONALE
Bromate forms when bromide reacts with ozone, especially at higher
pH and ozone dose. Lowering pH and reducing ozone dose or using
chloramines can minimize bromate while achieving required CT.
Increasing ozone worsens bromate; ammonia upstream of ozone is
ineffective and can create other issues.
Question 6
A utility is required to monitor for total coliforms under the Revised Total
Coliform Rule (RTCR). If a routine sample is total coliform-positive, what is
the next required action?
A. Immediately issue a boil water advisory
B. Collect repeat samples within 24 hours and conduct a sanitary survey
Page 4
PLANT OPERATOR CLASS 1 -5
CERTIFICATION EXAM
QUESTIONS AND VERIFIED
MARYLAND WATER TREATMENT PLANT OPERATOR CLASS
1 | Comprehensive Examination
MARYLAND WATER TREATMENT PLANT OPERATOR
CLASS 1 -5 CERTIFICATION EXAM QUESTIONS AND
VERIFIED ANSWERS.pdf actual exam preparation
INTRODUCTION
This document is an important and very helpful preparation
resource for MARYLAND WATER TREATMENT PLANT
OPERATOR CLASS 1 -5 CERTIFICATION EXAM
QUESTIONS AND VERIFIED ANSWERS.pdf. Every item
uses a focused exam stem, four response options, a keyed
response, and a clear rationale, making it easier to understand
the subject, spot distractors, and build real exam confidence.
Page 1
, Question 1
A surface water plant using alum coagulation experiences a sudden drop in raw
water alkalinity from 120 mg/L to 25 mg/L as CaCO3. Jar tests show optimal
alum dose at 40 mg/L but floc formation is poor and pH drops to 5.2. What is
the most appropriate operational adjustment?
A. Increase alum dose to 60 mg/L to compensate for reduced alkalinity
B. Add sodium hydroxide or soda ash to raise alkalinity and maintain pH
near 6.5-7.0
C. Switch to a non-ionic polymer as the primary coagulant
D. Reduce alum dose to 20 mg/L and increase flocculation time
Correct Answer: B - Add sodium hydroxide or soda ash to raise
alkalinity and maintain pH near 6.5-7.0
RATIONALE
Alum consumes alkalinity and lowers pH; at 25 mg/L alkalinity,
insufficient buffering causes pH to fall below the optimal coagulation
range. Adding alkali restores alkalinity and pH, improving floc
formation. Increasing alum worsens the problem, and non-ionic
polymers are not primary coagulants.
Question 2
A conventional filter with a surface area of 100 ft² operates at a filtration rate
of 4 gpm/ft². If the filter run is 30 hours, what is the total volume of water
filtered in gallons?
A. 720,000 gallons
B. 1,200,000 gallons
C. 12,000 gallons
D. 72,000 gallons
Correct Answer: A - 720,000 gallons
Page 2
, RATIONALE
Flow = 4 gpm/ft² × 100 ft² = 400 gpm. Over 30 hours = 400 × 60 × 30
= 720,000 gallons. Other options reflect arithmetic errors in unit
conversion or multiplication.
Question 3
A distribution system sample shows a chlorine residual of 0.2 mg/L free
chlorine at a dead-end main, while the treatment plant effluent has 1.0 mg/L.
What is the most likely cause?
A. Excessive chlorine demand from nitrification or biofilm in the
dead-end main
B. Chlorine decay due to high pH in the distribution system
C. Sample error from using a DPD colorimeter
D. Reduction of chlorine by fluoride addition at the plant
Correct Answer: A - Excessive chlorine demand from
nitrification or biofilm in the dead-end main
RATIONALE
Dead-end mains often experience stagnation, biofilm growth, and
nitrification, which consume free chlorine. A drop from 1.0 to 0.2
mg/L suggests significant demand. High pH would slow decay, not
accelerate it, and fluoride does not reduce chlorine.
Question 4
In a CT calculation for Giardia inactivation, if the disinfectant residual is 1.5
mg/L, the contact time is 20 minutes, and the peak hourly flow is 2.0 MGD,
what is the CT value (mg-min/L) assuming a baffling factor of 0.7?
A. 21 mg-min/L
B. 30 mg-min/L
C. 10.5 mg-min/L
D. 42 mg-min/L
Page 3
, Correct Answer: A - 21 mg-min/L
RATIONALE
CT = residual × effective contact time. Effective time = 20 min × 0.7 =
14 min. CT = 1.5 × 14 = 21 mg-min/L. Other options reflect omission
of baffling factor or incorrect multiplication.
Question 5
A plant using ozone for primary disinfection observes a sudden increase in
bromate formation in treated water. Which operational change is most effective
in reducing bromate while maintaining disinfection?
A. Increase ozone dose and contact time
B. Lower pH and reduce ozone dose, or switch to chloramine as
secondary disinfectant
C. Add ammonia upstream of ozone to form chloramines
D. Increase bromide removal by adding more coagulant
Correct Answer: B - Lower pH and reduce ozone dose, or switch
to chloramine as secondary disinfectant
RATIONALE
Bromate forms when bromide reacts with ozone, especially at higher
pH and ozone dose. Lowering pH and reducing ozone dose or using
chloramines can minimize bromate while achieving required CT.
Increasing ozone worsens bromate; ammonia upstream of ozone is
ineffective and can create other issues.
Question 6
A utility is required to monitor for total coliforms under the Revised Total
Coliform Rule (RTCR). If a routine sample is total coliform-positive, what is
the next required action?
A. Immediately issue a boil water advisory
B. Collect repeat samples within 24 hours and conduct a sanitary survey
Page 4
