Practice Exam 100 Questions And

Wastewater Collections Operator Class I Practice Exam – 100 Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• What is the primary purpose of a wastewater collection system?
• Deliver drinking water
• Convey wastewater to a treatment facility
• Store stormwater
• Remove solids from wastewater

Rationale: Collection systems are designed to move wastewater from its

source to the treatment plant.

2. A manhole’s invert is best described as:

• The top of the manhole
• The access steps
• The lowest point inside where flow enters or exits 1 / 3

• The diameter of the manhole

Rationale: The invert is the flow line and determines hydraulic grade.

• The recommended minimum velocity in gravity sewers to prevent solids

deposition is:

• 0.2 ft/s
• 1.0 ft/s
• 2.0 ft/s
• 5.0 ft/s

Rationale: A velocity of at least 2 ft/s helps keep solids in suspension.

• Hydrogen sulfide (H₂S) gas exposure primarily affects which human

sense first?

• Touch
• Smell
• Sight
• Taste

Rationale: H₂S has a rotten-egg odor detectable at very low

concentrations—until olfactory fatigue occurs.

• Which tool is used to measure depth of wastewater in a manhole?
• Flow meter
• Sludge judge or dipstick
• CCTV crawler 2 / 3

• Transit level

Rationale: A calibrated rod or judge gives a direct depth reading.

6. A combined sewer system carries:

• Drinking water and sewage
• Groundwater only
• Stormwater and sanitary wastewater
• Industrial wastewater only

Rationale: Combined systems convey both storm and sanitary flows.

7. Root intrusion in sewers is best controlled by:

• Increasing pipe pressure
• Chemical root treatment
• Adding more manholes
• Decreasing pipe slope

Rationale: Root-control chemicals prevent and remove root penetration.

8. A sewer with insufficient slope will likely experience:

• Increased velocity
• Sediment buildup
• Cavitation
• Pump cavitation

Rationale: Low slope reduces velocity and promotes solids deposition.

• When entering a confined space, the first safety step is to:
• / 3