Operator Grade IV Practice Exam

Tennessee Wastewater Treatment Operator Grade IV Practice Exam Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• What is the primary purpose of a grit chamber in wastewater

treatment?

• Remove organic matter
• Remove sand, gravel, and heavy solids
• Remove dissolved chemicals
• Aerate wastewater

Rationale: Grit chambers are designed to remove heavy inorganic

solids like sand and gravel to prevent abrasion and settling issues in downstream equipment. 1 / 4

• Which of the following is a common method for measuring sludge

volume?

• pH meter
• Imhoff cone
• Turbidity meter
• Flow meter

Rationale: An Imhoff cone is a conical container used to measure the

volume of settled sludge after a set period, typically 30 minutes.

3. Nitrification in a biological treatment process converts:

• Ammonia to nitrate
• Nitrite to ammonia
• Ammonia to nitrite and then nitrate
• Nitrate to nitrogen gas

Rationale: Nitrification is a two-step process: ammonia is first converted to nitrite by ammonia-oxidizing bacteria and then to nitrate by nitrite-oxidizing bacteria.

• Which of the following is a sign of filamentous bulking in activated

sludge?

• Rapid settling
• Clear effluent
• Poor sludge settling
• High dissolved oxygen 2 / 4

Rationale: Filamentous bacteria can grow excessively, causing sludge

to float and settle poorly, resulting in bulking.

5. The primary purpose of chlorination in wastewater treatment is to:

• Reduce BOD
• Remove solids
• Disinfect the effluent
• Remove nutrients

Rationale: Chlorination is primarily used to inactivate pathogenic

microorganisms to protect public health.

• What is the typical pH range for nitrification to occur efficiently?

A. 4.5–5.5

B. 9.0–10.5

C. 6.0–7.0

D. 6.5–8.5

Rationale: Nitrifying bacteria are sensitive to pH and perform best in

a slightly alkaline range between 6.5 and 8.5.

• Which factor most affects the rate of biological treatment in an

activated sludge system?

• Influent color
• Temperature
• Flow rate only
• Odor

Rationale: Biological activity is strongly influenced by temperature; 3 / 4

higher temperatures generally increase microbial activity up to an optimal point.

• What is the main purpose of a secondary clarifier?
• Remove grit
• Settle biological solids after aeration
• Reduce BOD chemically
• Disinfect effluent

Rationale: Secondary clarifiers allow the separation of activated

sludge biomass from the treated wastewater for return or disposal.

• Which type of sludge digestion reduces volatile solids and produces

methane gas?

• Aerobic digestion
• Anaerobic digestion
• Gravity thickening
• Chemical precipitation

Rationale: Anaerobic digestion breaks down organic matter in the

absence of oxygen, reducing volatile solids and generating methane as a byproduct.

10. The purpose of aeration in activated sludge systems is to:

• Remove grit
• Provide oxygen for microbial activity
• Settle solids
• Remove nutrients
• / 4