Operator Grade 1 Exam Practice Questions

Rhode Island Wastewater Treatment Operator Grade 1 Exam Practice Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• What is the primary purpose of a wastewater treatment plant?
• Produce drinking water
• Remove pollutants from wastewater before discharge
• Generate electricity
• Store sewage

Rationale: The main goal of a wastewater treatment plant is to remove

contaminants from sewage or industrial wastewater to protect public health and the environment.

• Which of the following is considered a primary treatment process?
• Activated sludge process 1 / 4

• Sedimentation in primary clarifiers
• Trickling filters
• Chlorination

Rationale: Primary treatment involves physical processes like screening

and sedimentation to remove settleable solids.

• What is the typical BOD removal efficiency of primary treatment?

A. 10-20%

B. 25-40%

C. 50-60%

D. 70-80%

Rationale: Primary sedimentation generally removes 25-40% of the

incoming biochemical oxygen demand (BOD).

• Which of the following is a characteristic of domestic sewage?
• High industrial chemicals
• Contains organic matter, nutrients, and microorganisms
• Only stormwater
• Pure water

Rationale: Domestic sewage is primarily composed of water, organic

matter, nutrients like nitrogen and phosphorus, and microorganisms.

• What is the function of a bar screen in wastewater treatment?
• Remove dissolved solids
• Remove bacteria 2 / 4

• Remove large debris and solids
• Aerate the wastewater

Rationale: Bar screens are designed to remove large objects such as sticks,

rags, and plastics that could damage downstream equipment.

• Which process is used to remove suspended solids after primary

treatment?

• Chlorination
• Filtration
• Secondary biological treatment
• Sedimentation

Rationale: Secondary treatment typically uses biological processes to

degrade remaining organic matter and remove suspended solids.

7. In an aeration tank, oxygen is supplied to:

• Kill bacteria
• Remove solids
• Support aerobic bacteria in breaking down organic matter
• Clarify water

Rationale: Aerobic bacteria require oxygen to metabolize organic matter,

reducing BOD in wastewater.

• What is sludge?
• Pure water
• The solid material separated from wastewater during treatment 3 / 4

• Dissolved oxygen
• Chlorine byproduct

Rationale: Sludge consists of settleable solids removed during primary and

secondary treatment.

• What is the purpose of chlorination in wastewater treatment?
• Remove solids
• Remove nutrients
• Disinfect treated effluent
• Aerate water

Rationale: Chlorination is a disinfection process that kills or inactivates

pathogens in treated wastewater.

• Which of the following indicates oxygen demand in wastewater?
• pH
• Temperature
• Biochemical Oxygen Demand (BOD)
• Conductivity

Rationale: BOD measures the amount of oxygen microorganisms consume

while decomposing organic matter in water.

11. The normal range of pH in municipal wastewater is:

A. 2-4

• 5-6
• / 4