Water Distribution Operator Certification Exam: Key
Concepts and Math Practice exam actual real questions
and answers with complete solutions verified latest
update 2026/2027
What is cavitation in a water main? Cavitation is the formation of
vapor bubbles in a
liquid due to pressure drops, which can
lead to damage in the water main.
What is calcium hypochlorite? Calcium hypochlorite is a chemical
compound
used as a disinfectant that contains
approximately 65% available chlorine.
What chemical neutralizes chlorine Sodium thiosulfate is
commonly used to neutralize residual in water? chlorine
residual in water samples.
,What is nitrification? Nitrification is the biological
process where bacteria convert
ammonia to nitrite and then to
nitrate in a chloraminated
distribution system.
What causes trihalomethanes in Trihalomethanes are most
likely caused by the water? byproduct of chlorination in water
treatment.
What indicates bacterial A sudden drop in chlorine
residual to zero is an contamination in a water system?
indication that bacterial
contamination may have
entered the distribution system.
What factors affect the disinfection Factors include
temperature of the water, water power of chlorine?
hardness, contact time, and pH of
, the water.
What signifies breakpoint Breakpoint chlorination is
achieved when no chlorination? chlorine residual is
detected in the water after
chlorination.
What is required before using Negative bacteriological test
results must be disinfected pumps and tanks? obtained
before putting disinfected pumps, tanks,
and water mains back into use.
What does a positive coliform test A positive result for a coliform
presence/absence indicate? test indicates potential biological
contamination.
What is a primary MCL? A primary Maximum Contaminant Level
(MCL) is a
standard for contaminants in
drinking water that may adversely
affect human health.
Concepts and Math Practice exam actual real questions
and answers with complete solutions verified latest
update 2026/2027
What is cavitation in a water main? Cavitation is the formation of
vapor bubbles in a
liquid due to pressure drops, which can
lead to damage in the water main.
What is calcium hypochlorite? Calcium hypochlorite is a chemical
compound
used as a disinfectant that contains
approximately 65% available chlorine.
What chemical neutralizes chlorine Sodium thiosulfate is
commonly used to neutralize residual in water? chlorine
residual in water samples.
,What is nitrification? Nitrification is the biological
process where bacteria convert
ammonia to nitrite and then to
nitrate in a chloraminated
distribution system.
What causes trihalomethanes in Trihalomethanes are most
likely caused by the water? byproduct of chlorination in water
treatment.
What indicates bacterial A sudden drop in chlorine
residual to zero is an contamination in a water system?
indication that bacterial
contamination may have
entered the distribution system.
What factors affect the disinfection Factors include
temperature of the water, water power of chlorine?
hardness, contact time, and pH of
, the water.
What signifies breakpoint Breakpoint chlorination is
achieved when no chlorination? chlorine residual is
detected in the water after
chlorination.
What is required before using Negative bacteriological test
results must be disinfected pumps and tanks? obtained
before putting disinfected pumps, tanks,
and water mains back into use.
What does a positive coliform test A positive result for a coliform
presence/absence indicate? test indicates potential biological
contamination.
What is a primary MCL? A primary Maximum Contaminant Level
(MCL) is a
standard for contaminants in
drinking water that may adversely
affect human health.
