Operator Class 4 Practice Exam 100

Maryland Wastewater Treatment Operator Class 4 Practice Exam 100 Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• What is the primary purpose of preliminary treatment in a wastewater

plant?

• Reduce nitrogen
• Remove dissolved solids
• Remove large debris
• Disinfect wastewater

Rationale: Preliminary treatment removes rags, grit, and large materials to

protect downstream equipment.

• Grit chambers are designed to remove particles with what general

settling characteristic? 1 / 3

• Slow settling
• Non-settling
• Fast settling
• Neutral buoyancy

Rationale: Grit consists of dense, rapidly settling inorganic particles.

• Which type of pump is most commonly used for sludge transfer?
• Centrifugal pump
• Positive displacement pump
• Jet pump
• Turbine pump

Rationale: Positive displacement pumps handle thick, viscous sludge

effectively.

4. In an activated sludge process, a low F/M ratio typically results in:

• High suspended solids
• Poor settling
• Older sludge with good settling
• Bulking sludge

Rationale: Low F/M produces well-stabilized sludge with improved

settling.

5. Chlorine reacts with ammonia to form:

• Free chlorine
• Chloramines 2 / 3

• Ozone
• Hydroxides

Rationale: Chlorine + ammonia = chloramines, used in disinfection.

• Which laboratory test determines the oxygen-consuming capability of

wastewater?

A. TSS

B. BOD

• Conductivity
• pH

Rationale: BOD measures biodegradable organic load.

7. A clarifier’s sludge blanket should be monitored to prevent:

• Flash mixing
• Solids washout
• Over-chlorination
• Excess aeration

Rationale: High blankets can cause solids to escape with effluent.

8. A key operational indicator of nitrification is:

• High CBOD
• High pH
• Low ammonia levels
• High turbidity
• / 3