Exam Practice Questions And Correct

Missouri Wastewater Operator Class B Exam Practice Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• What is the primary purpose of a wastewater treatment plant?
• Produce drinking water
• Remove contaminants from wastewater
• Generate electricity
• Provide irrigation water
• Remove contaminants from wastewater

Rationale: The main goal of a wastewater treatment plant is to

remove pollutants and protect public health and the environment.

• Which of the following is the most common method for primary

treatment? 1 / 4

• Filtration
• Sedimentation
• Chlorination
• Aeration
• Sedimentation

Rationale: Primary treatment usually involves sedimentation to

remove settleable solids.

• What is BOD a measure of in wastewater?
• Chemical contamination
• Biological oxygen demand
• Water hardness
• pH level
• Biological oxygen demand

Rationale: BOD measures the amount of oxygen microorganisms need

to decompose organic matter in water.

• Which type of bacteria is primarily responsible for nitrification in

wastewater?

• Coliform bacteria
• Nitrosomonas and Nitrobacter
• Clostridium
• E. coli
• Nitrosomonas and Nitrobacter 2 / 4

Rationale: Nitrosomonas converts ammonia to nitrite, and Nitrobacter

converts nitrite to nitrate in nitrification.

• What is the function of an aeration tank in secondary treatment?
• Settle solids
• Promote microbial digestion of organic matter
• Remove chlorine
• Filter water
• Promote microbial digestion of organic matter

Rationale: Aeration provides oxygen for microorganisms to break

down organic pollutants.

6. Sludge age is a term used to describe:

• The time wastewater spends in primary clarifiers
• The average time solids remain in the biological treatment system
• The age of the treatment plant
• The time sludge spends in drying beds
• The average time solids remain in the biological treatment system

Rationale: Sludge age, or solids retention time, impacts microbial

population and treatment efficiency.

• What is the main purpose of disinfection in wastewater treatment?
• Remove suspended solids
• Kill pathogenic organisms
• Reduce BOD
• Remove nutrients 3 / 4

• Kill pathogenic organisms

Rationale: Disinfection ensures that harmful microorganisms are

reduced to safe levels before discharge.

• Which chemical is commonly used for disinfection in wastewater

treatment?

• Sodium hydroxide
• Chlorine
• Ammonia
• Calcium carbonate
• Chlorine

Rationale: Chlorine is widely used because it effectively kills bacteria

and other pathogens.

• Which parameter is most affected by stormwater infiltration into a

sanitary sewer system?

A. BOD

• Flow rate
• pH
• Chlorine residual
• Flow rate

Rationale: Infiltration increases the volume of wastewater entering

the system, affecting flow rates and treatment.

10. The term “secondary clarifier” refers to a unit that:

• Removes grit
• / 4