Class I Practice Exam Questions And

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

• What is the primary objective of industrial wastewater treatment?
• To produce drinking water
• To remove contaminants before discharge
• To increase water hardness
• To improve taste and odor

Rationale: The main goal is to reduce pollutants to acceptable

discharge levels.

• Which physical process removes suspended solids from wastewater?
• Biological oxidation
• Chemical precipitation
• Sedimentation 1 / 3

• Nitrification

Rationale: Sedimentation separates solids by gravity.

• What is the purpose of an equalization basin?
• To disinfect wastewater
• To balance flow and load variations
• To thicken sludge
• To remove oil and grease

Rationale: Equalization stabilizes flow and pollutant concentrations

before treatment.

4. The term BOD stands for:

• Biochemical Oxygen Demand
• Biological Oxidation Demand
• Basic Oxygen Dissolution
• Biochemical Oxidation Density

Rationale: BOD measures the oxygen required for microbial

decomposition of organics.

5. A high BOD value indicates:

• Low organic pollution
• No organic matter
• High organic pollution
• High dissolved oxygen

Rationale: More organic matter means more oxygen is needed for

decomposition. 2 / 3

• Which device measures wastewater flow?
• Turbidity meter
• Flowmeter
• DO probe
• Manometer

Rationale: Flowmeters measure the rate of liquid movement through

pipes or channels.

• Which parameter indicates the clarity of water?
• pH
• Turbidity

C. BOD

D. COD

Rationale: Turbidity measures suspended particle concentration

affecting water clarity.

• What is the typical pH range for biological treatment?

A. 2–4

B. 6.5–8.5

C. 9–11

D. 4–5

Rationale: Most microorganisms thrive in near-neutral pH conditions.

9. The main function of an aeration tank is to:

• Supply oxygen for microbial activity
• Remove solids by gravity
• / 3