Grade 1 Wastewater Treatment Practice Questions

What is the primary purpose of bar screens in preliminary wastewater treatment?

• ATo remove dissolved solids
• BTo remove large debris and rags that could damage downstream equipment
• CTo reduce BOD
• DTo disinfect the influent

A tank holds 50,000 gallons and receives a flow of 100,000 gallons per day. What is the detention time?

• A6 hours
• B12 hours
• C24 hours
• D48 hours

What is the primary purpose of grit removal in preliminary wastewater treatment?

• ATo remove dissolved organics
• BTo remove heavy inorganic material like sand and gravel that could damage pumps or settle in pipes
• CTo disinfect the wastewater
• DTo remove nitrogen

A primary clarifier has a surface area of 1,000 ft² and receives a flow of 1.0 MGD. What is the surface overflow rate?

• A100 gpd/ft²
• B500 gpd/ft²
• C1,000 gpd/ft²
• D10,000 gpd/ft²

Why is dechlorination often required after disinfecting wastewater effluent with chlorine?

• ATo increase the effluent's chlorine residual
• BTo neutralize residual chlorine before discharge, since it is toxic to aquatic life
• CTo reduce BOD
• DTo add nutrients back to the water