Operator S1 Practice Exam Questions

New Jersey Wastewater Treatment Operator S1 Practice Exam Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• Which of the following best describes BOD in wastewater?
• Biological Oxidation Demand
• Biochemical Oxygen Demand
• Basic Oxygen Depletion
• Biological Oxygen Determination

Answer: B

Rationale: BOD measures the amount of oxygen microorganisms consume

to decompose organic matter in water over a specific period, indicating wastewater strength.

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• What is the primary purpose of screening in wastewater treatment?
• Remove dissolved nutrients
• Remove large solids and debris
• Reduce BOD
• Neutralize pH

Answer: B

Rationale: Screens remove rags, sticks, plastics, and other large debris to

prevent damage or clogging in downstream equipment.

• Which microorganism group primarily carries out biological treatment in

activated sludge systems?

• Viruses
• Algae
• Bacteria
• Protozoa

Answer: C

Rationale: Bacteria are the main decomposers that metabolize organic

pollutants in activated sludge processes.

• In the activated sludge process, what is the function of the aeration

tank?

• Sediment solids 2 / 4

• Provide oxygen for microbial degradation
• Screen solids
• Clarify effluent

Answer: B

Rationale: Aeration tanks supply oxygen to microorganisms so they can

break down organic matter efficiently.

• What is the typical dissolved oxygen (DO) range maintained in an

aeration tank?

• 0–1 mg/L
• 1–2 mg/L
• 2–4 mg/L
• 5–8 mg/L

Answer: C

Rationale: Maintaining 2–4 mg/L DO ensures microbial activity is optimal

without wasting energy on excessive aeration.

6. The pH of typical domestic wastewater is usually:

A. 2–4

B. 4–5

C. 6–8

D. 9–10 3 / 4

Answer: C

Rationale: Domestic wastewater generally has a neutral to slightly alkaline

pH, suitable for biological treatment.

• What does TSS stand for in wastewater terminology?
• Total Soluble Substances
• Total Sulfur Solids
• Total Suspended Solids
• Total Soluble Solids

Answer: C

Rationale: TSS refers to particles suspended in water, an important

parameter for treatment and regulatory compliance.

• Which process is used primarily for nutrient removal (nitrogen and

phosphorus)?

• Filtration
• Chlorination
• Biological nutrient removal
• Sedimentation

Answer: C

Rationale: Biological nutrient removal uses specialized microorganisms to

reduce nitrogen and phosphorus in wastewater.

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