Operator Certification Practice Exam

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

• What is the main objective of wastewater treatment in metal finishing

operations?

• To enhance product shine
• To remove pollutants before discharge
• To cool down metal parts
• To recycle plating solution

Rationale: The purpose is to remove contaminants such as heavy metals,

cyanide, and suspended solids before wastewater is discharged to comply with environmental regulations.

• Which metal is most commonly regulated in electroplating waste

streams? 1 / 4

• Aluminum
• Chromium
• Sodium
• Calcium

Rationale: Chromium from chrome plating is a key regulated pollutant due

to its toxicity and environmental persistence.

3. The pH adjustment step in wastewater treatment is primarily used to:

• Increase temperature
• Remove oils
• Optimize metal precipitation
• Sterilize the water

Rationale: Proper pH ensures effective precipitation of metal hydroxides

during chemical treatment.

• The best method for removing suspended solids after chemical

precipitation is:

• Aeration
• Ion exchange
• Clarification or sedimentation
• pH adjustment

Rationale: Clarifiers allow heavier particles to settle, separating solids from

treated water. 2 / 4

• What chemical is commonly used to reduce hexavalent chromium (Cr⁶⁺)

to trivalent chromium (Cr³⁺)?

• Hydrogen peroxide
• Sodium hydroxide
• Sodium metabisulfite
• Ammonia

Rationale: Sodium metabisulfite is a standard reducing agent in chrome

reduction reactions.

• Cyanide wastes are detoxified by which two-step process?
• Neutralization and oxidation
• Chlorination and oxidation
• Precipitation and filtration
• Sedimentation and aeration

Rationale: Cyanide is oxidized using chlorine compounds to form less toxic

cyanates, then further oxidized to carbon dioxide and nitrogen.

• Which parameter indicates the strength of organic pollution in

wastewater?

A. TSS

B. BOD 3 / 4

• Conductivity
• pH

Rationale: Biochemical Oxygen Demand (BOD) measures oxygen consumed

by microbes decomposing organic matter.

8. Sludge from metal finishing treatment typically contains:

• Sand and silt
• Metal hydroxides
• Organic acids
• Chlorinated solvents

Rationale: Metal hydroxides form during precipitation and accumulate in

sludge.

• What type of pump is best suited for transferring sludge?
• Centrifugal pump
• Positive displacement pump
• Jet pump
• Magnetic drive pump

Rationale: Positive displacement pumps handle high-viscosity materials

like sludge efficiently.

• / 4