Treatment Operator Exam Level I Practice

British Columbia ROWP Wastewater Treatment Operator Exam Level I Practice Exam Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• What is the primary purpose of a residential onsite wastewater

treatment system?

• To generate reusable water for irrigation
• To disinfect wastewater to drinking-water standards
• To remove contaminants before discharge to the soil
• To reduce solid waste only
• To remove contaminants before discharge to the soil

Rationale: The goal is to reduce organic load, pathogens, and solids so soil

can complete final treatment.

• What is the typical function of a septic tank in an onsite system? 1 / 4

• Aerobic digestion
• Chemical treatment
• Primary settling and anaerobic digestion
• Filtration

Rationale: Septic tanks settle solids and support anaerobic digestion before

effluent moves to the dispersal system.

3. The scum layer in a septic tank consists mainly of:

• Gravel and sand
• Grease, oils, and floatable materials
• Settleable solids
• Pathogens

Rationale: Light materials float to form the scum layer.

4. The sludge layer in a septic tank is composed of:

• Floatable solids
• Settleable solids that accumulate on the bottom
• Fully digested effluent
• Fats, oils, and grease

Rationale: Heavy solids settle and form sludge at the tank bottom.

• Why are baffles or tees important in a septic tank?
• To add oxygen for aerobic treatment
• To remove nutrients
• To prevent scum and sludge from exiting the tank 2 / 4

• To disinfect the effluent

Rationale: Baffles ensure only clarified effluent leaves the tank.

• Which type of soil provides the best treatment capacity for onsite

effluent?

• Gravel
• Clay
• Loam
• Bedrock

Rationale: Loam provides ideal balance of permeability and treatment.

• What does hydraulic loading rate (HLR) refer to?
• Organic strength of wastewater
• Size of the septic tank
• Volume of effluent applied per area of soil per day
• Amount of sludge produced

Rationale: HLR determines how much water soil can accept.

• Which wastewater parameter indicates organic strength?
• pH

B. BOD

C. TSS

• Turbidity

Rationale: Biochemical Oxygen Demand measures organic loading.

• The BC Sewerage System Regulation is administered by: 3 / 4

• Health Canada
• Ministry of Environment
• Health Authorities
• Municipal Councils

Rationale: Local Health Authorities oversee ROWP practitioner work under

provincial regulation.

• A ROWP must follow which professional guideline when conducting

work?

• National Plumbing Code
• Mechanical Contractors Act
• ASTTBC Practice Guidelines
• Canadian Electrical Code

Rationale: ASTTBC governs certification and practice of ROWPs in BC.

• What happens if effluent is applied too quickly to soil?
• Faster treatment
• Soil saturation and system failure
• Increased disinfection
• Greater aeration

Rationale: Excess application leads to ponding and failure.

• What is the purpose of an effluent filter?
• / 4