Operator Certification Practice Exam

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

(Comprehensive coverage: physical, chemical, and biological treatment

processes, regulations, safety, and operations)

• Which parameter best indicates the strength of an industrial

wastewater in terms of organic content?

• Suspended solids
• Chemical oxygen demand (COD)
• pH
• Conductivity

Rationale: COD measures the total quantity of oxygen required to

chemically oxidize organic and inorganic matter, indicating organic strength. 1 / 4

• The primary purpose of equalization tanks in industrial wastewater

treatment is to:

• Increase BOD removal efficiency
• Reduce flow and load fluctuations
• Improve sludge settling
• Remove heavy metals

Rationale: Equalization stabilizes flow rate and pollutant concentration to

protect downstream processes from shock loads._

3. A jar test is used to determine:

• Solids retention time
• Sludge volume index
• Optimal coagulant dosage
• Filter press pressure

Rationale: Jar tests simulate coagulation-flocculation conditions to find the

most effective chemical dose and pH._

• Which metal hydroxide precipitates best at a pH of about 9.5?
• Iron
• Nickel
• Zinc 2 / 4

• Chromium

Rationale: Zinc hydroxide achieves minimum solubility around pH 9.5,

making precipitation most effective._

5. The activated sludge process primarily removes:

• Suspended solids
• Biodegradable organic matter
• Dissolved minerals
• Heavy metals

Rationale: The process relies on microorganisms to metabolize organic

pollutants into biomass and CO₂._

• Which parameter is most critical for controlling an activated sludge

system?

• Influent COD
• Sludge age (SRT)
• Temperature
• DO saturation level

Rationale: Sludge age determines the microbial population balance and

system stability._

• / 4

7. The term “F/M ratio” refers to:

• Food-to-microorganism ratio
• Flow-to-mass ratio
• Filtration-to-mixing ratio
• Feed-to-media ratio

Rationale: F/M defines the organic loading relative to microbial mass and

guides process control._

8. The primary cause of filamentous bulking in activated sludge is:

• Excessive aeration
• Low F/M ratio and nutrient imbalance
• High temperature
• High pH

Rationale: Low substrate availability and nutrient imbalance favor

filamentous bacteria growth, causing poor settling._

• Which process uses high pressure to remove dissolved salts from

wastewater?

• Ion exchange
• Electrodialysis
• Reverse osmosis
• Ultrafiltration
• / 4