NCEES Environmental Engineering PE Exam 1 — Questions and Answers
Question 1: On the NCEES PE Environmental exam, which process is used in a conventional drinking water treatment plant to remove suspended particles after coagulation and flocculation?
- Reverse osmosis
- Sedimentation (clarification) (Correct answer)
- Ion exchange
- Ultraviolet disinfection
Correct answer: Sedimentation (clarification)
After coagulation and flocculation form larger floc particles, sedimentation (settling in clarifiers) removes the floc by gravity before filtration.
Question 2: In the NCEES PE Environmental exam, what does 'BOD5' measure in wastewater analysis?
- Biological oxygen demand of soil samples over 5 years
- The amount of dissolved oxygen consumed by microorganisms decomposing organic matter in 5 days at 20°C (Correct answer)
- The pH change over 5 days of aerobic treatment
- The concentration of total dissolved solids after 5-day settling
Correct answer: The amount of dissolved oxygen consumed by microorganisms decomposing organic matter in 5 days at 20°C
BOD5 (5-day biochemical oxygen demand) measures the oxygen consumed by microbial decomposition of organic matter in water over 5 days at 20°C, indicating organic pollution strength.
Question 3: For the NCEES PE Environmental exam, what is the primary purpose of chlorination in drinking water treatment in the US?
- To remove heavy metals such as lead and arsenic
- To inactivate pathogenic microorganisms and provide residual disinfection in the distribution system (Correct answer)
- To soften hard water by precipitating calcium
- To remove taste and odor compounds
Correct answer: To inactivate pathogenic microorganisms and provide residual disinfection in the distribution system
Chlorination disinfects drinking water by inactivating pathogens and maintaining a disinfectant residual throughout the distribution system as required by the Safe Drinking Water Act.
Question 4: On the NCEES PE Environmental exam, what is the 'hydraulic retention time (HRT)' of a wastewater treatment reactor?
- The time solids remain in the reactor before wasting
- The average time water (liquid) spends in the reactor, equal to volume divided by flow rate (Correct answer)
- The time between backwash cycles in a filter
- The contact time for disinfection
Correct answer: The average time water (liquid) spends in the reactor, equal to volume divided by flow rate
HRT = V/Q (volume/flow), representing the average residence time of liquid in the reactor, which determines treatment effectiveness for time-dependent reactions.
Question 5: In the NCEES PE Environmental exam, which US regulation sets National Primary Drinking Water Regulations (NPDWRs)?
- Clean Water Act (CWA)
- Resource Conservation and Recovery Act (RCRA)
- Safe Drinking Water Act (SDWA) (Correct answer)
- Comprehensive Environmental Response Act (CERCLA)
Correct answer: Safe Drinking Water Act (SDWA)
The Safe Drinking Water Act (SDWA) authorizes EPA to establish National Primary Drinking Water Regulations, including maximum contaminant levels (MCLs) for public water systems.
Question 6: For the NCEES PE Environmental exam, what is 'eutrophication' of a water body caused by?
- Acid mine drainage lowering pH
- Excessive nutrient (nitrogen and phosphorus) loading stimulating algal growth and depleting oxygen (Correct answer)
- Heavy metal contamination from industrial discharge
- Thermal pollution from power plant cooling water
Correct answer: Excessive nutrient (nitrogen and phosphorus) loading stimulating algal growth and depleting oxygen
Eutrophication results from excessive nitrogen and phosphorus inputs (agriculture, wastewater) that fuel algal blooms; when algae die and decompose, dissolved oxygen is depleted, creating hypoxic zones.
NCEES Environmental Engineering PE Exam 1
On the NCEES PE Environmental exam, which process is used in a conventional drinking water treatment plant to remove suspended particles after coagulation and flocculation?