IV Certification Practice Exam Questions

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

• What is the primary objective of industrial waste treatment?

a) Increase production efficiency

b) Reduce pollutants before discharge

c) Improve product quality

d) Increase water hardness

Rationale: The goal is to remove or reduce contaminants in wastewater

before it is discharged to protect public health and the environment.

• Which of the following best describes “BOD”?

a) Biological Oxygen Displacement

b) Biochemical Oxygen Demand

c) Basic Oxygen Degradation 1 / 4

d) Biocatalytic Oxidation Density

Rationale: BOD measures the oxygen required by microorganisms to

decompose organic matter, indicating organic pollution levels.

3. High BOD in wastewater indicates:

a) Low organic content

b) High pH

c) High organic content

d) Low microbial activity

Rationale: A high BOD reflects a large amount of biodegradable material in

the water.

4. The pH of typical industrial wastewater is controlled to:

• 2–4
• 6–9
• 10–12
• 4–6

Rationale: Effluent permits usually require pH between 6 and 9 for safe

discharge.

5. A clarifier removes:

a) Dissolved gases 2 / 4

b) Suspended solids

c) Dissolved salts

d) Odors

Rationale: Clarifiers settle out suspended solids by gravity.

• What is the purpose of an equalization tank?

a) Increase sludge production

b) Balance flow and concentration variations

c) Aerate wastewater

d) Add disinfectant

Rationale: Equalization tanks stabilize influent conditions for consistent

downstream treatment.

7. The activated sludge process primarily removes:

a) Inorganic solids

b) Organic matter

c) Heavy metals

d) Nutrients only

Rationale: It relies on microorganisms to oxidize organic materials.

• What is the function of a trickling filter?

a) Chemical neutralization 3 / 4

b) Coagulation

c) Biological oxidation

d) Sedimentation

Rationale: A trickling filter uses biofilm on media for aerobic biological

treatment.

9. The main purpose of sludge digestion is:

a) Stabilize organic matter

b) Increase solids volume

c) Remove metals

d) Reduce pH

Rationale: Digestion converts unstable organics into stable forms and

reduces odors.

• What type of microorganisms dominate in aerobic digestion?

a) Aerobes

b) Anaerobes

c) Facultative bacteria

d) Sulfate reducers

Rationale: Aerobic digestion relies on oxygen-utilizing bacteria.

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