CME CME Water & Wastewater Systems 2 — Questions and Answers
Question 1: What is the purpose of a sanitary sewer system's lift (pump) station?
- Remove grit and debris from sewage
- Pump wastewater to a higher elevation when gravity flow is not feasible (Correct answer)
- Provide primary treatment of sewage
- Control combined sewer overflow events
Correct answer: Pump wastewater to a higher elevation when gravity flow is not feasible
Lift stations pump sewage uphill to overcome topographic barriers where gravity-only sewer routing is impractical or uneconomical.
Question 2: Which treatment process removes the majority of suspended solids and biochemical oxygen demand (BOD) in secondary wastewater treatment?
- Screening and grit removal
- Primary clarification
- Activated sludge or biological treatment (Correct answer)
- Chlorination and disinfection
Correct answer: Activated sludge or biological treatment
Secondary treatment using activated sludge or other biological processes removes 85–95% of BOD and suspended solids through microbial action.
Question 3: What document establishes the effluent limits a municipal wastewater treatment plant must meet when discharging to a water body?
- MS4 Permit
- NPDES Permit (Correct answer)
- TMDL Report
- NOI for Construction
Correct answer: NPDES Permit
An NPDES (National Pollutant Discharge Elimination System) permit sets the specific effluent limits a treatment plant must meet under the Clean Water Act.
Question 4: In sewer system design, what does 'peaking factor' account for?
- Maximum pipe slope allowed
- Ratio of peak instantaneous flow to average daily flow used for sizing sewers (Correct answer)
- Infiltration/inflow from groundwater
- Storm runoff contributing to combined sewers
Correct answer: Ratio of peak instantaneous flow to average daily flow used for sizing sewers
The peaking factor is applied to average daily flows to size sewers and treatment facilities for the highest expected instantaneous or peak-hour flows.
Question 5: Which sewer rehabilitation method installs a resin-impregnated liner inside an existing pipe without excavation?
- Slip lining
- Cured-in-place pipe (CIPP) (Correct answer)
- Pipe bursting
- Spray-on lining
Correct answer: Cured-in-place pipe (CIPP)
CIPP (cured-in-place pipe) involves inserting a resin-saturated felt tube and curing it in place to form a new pipe inside the deteriorated host pipe without digging.
Question 6: What is the primary concern with combined sewer overflows (CSOs) in older US cities?
- Excess potable water waste
- Discharge of untreated sewage and stormwater to waterways during rain events (Correct answer)
- Increased water pressure in distribution mains
- Loss of chlorine residual in drinking water
Correct answer: Discharge of untreated sewage and stormwater to waterways during rain events
CSOs occur when combined sewers overflow during storms, releasing untreated sewage mixed with stormwater directly into receiving waters, causing significant water quality impairment.
CME CME Water & Wastewater Systems 2
What is the purpose of a sanitary sewer system's lift (pump) station?