Energy and Utilities Water and Wastewater Utilities 2 — Questions and Answers
Question 1: What does 'BOD' stand for in wastewater treatment?
- Biological Oxygen Demand
- Biochemical Oxygen Demand (Correct answer)
- Basic Organic Discharge
- Buffered Output Dosage
Correct answer: Biochemical Oxygen Demand
Biochemical Oxygen Demand (BOD) measures the amount of dissolved oxygen microbes consume when decomposing organic matter in water.
Question 2: What is 'primary treatment' in a conventional wastewater treatment plant?
- Biological degradation of organic matter
- Physical removal of settleable solids and floating material by screening and sedimentation (Correct answer)
- Chemical precipitation of phosphorus
- Disinfection with UV or chlorine
Correct answer: Physical removal of settleable solids and floating material by screening and sedimentation
Primary treatment uses physical processes — bar screens, grit chambers, and primary clarifiers — to remove large solids and floatable material from wastewater.
Question 3: What does NPDES stand for in the context of US water regulation?
- National Pollution Discharge Elimination System (Correct answer)
- Natural Processing of Dissolved Environmental Solids
- National Primary Drinking water Enforcement Standard
- Non-Point Discharge and Environmental Screening
Correct answer: National Pollution Discharge Elimination System
The National Pollutant Discharge Elimination System (NPDES) is the EPA permit program under the Clean Water Act that controls water pollution by regulating point source discharges.
Question 4: What is 'water loss' or 'non-revenue water' in distribution system management?
- Water used for fire suppression
- Water that enters the distribution system but is not billed to customers due to leaks, theft, or metering errors (Correct answer)
- Water reserved for drought emergencies
- Water used in treatment plant operations
Correct answer: Water that enters the distribution system but is not billed to customers due to leaks, theft, or metering errors
Non-revenue water is the difference between water input to the distribution system and water billed to customers, including physical losses from leaks and apparent losses from theft.
Question 5: What is the purpose of a 'water hammer' arrestor in plumbing systems?
- Preventing backflow contamination
- Absorbing pressure surges from rapid valve closure to protect pipes (Correct answer)
- Reducing water pressure at the meter
- Filtering sediment from water
Correct answer: Absorbing pressure surges from rapid valve closure to protect pipes
Water hammer arrestors use a sealed air chamber or spring piston to absorb the hydraulic shock wave created when flowing water is suddenly stopped.
Question 6: What is 'digestion' in the biosolids treatment process at a wastewater plant?
- Chemical treatment to neutralize pH
- Biological decomposition of organic matter in sludge to reduce volume and pathogens (Correct answer)
- Mechanical dewatering of sludge
- Blending sludge with disinfectants
Correct answer: Biological decomposition of organic matter in sludge to reduce volume and pathogens
Anaerobic or aerobic digestion uses microorganisms to break down organic material in sludge, reducing volume, stabilizing solids, and producing biogas.
Energy and Utilities Water and Wastewater Utilities 2
What does 'BOD' stand for in wastewater treatment?