ETC Water Quality & Treatment 1 — Questions and Answers
Question 1: Which federal law establishes Maximum Contaminant Levels (MCLs) for drinking water contaminants and is enforced by the EPA?
- Clean Water Act (CWA)
- Safe Drinking Water Act (SDWA) (Correct answer)
- Resource Conservation and Recovery Act (RCRA)
- Toxic Substances Control Act (TSCA)
Correct answer: Safe Drinking Water Act (SDWA)
The Safe Drinking Water Act (SDWA) authorizes the EPA to set and enforce MCLs and treatment technique requirements for public water systems to protect public health.
Question 2: In wastewater treatment, what is Biochemical Oxygen Demand (BOD) a measure of?
- The concentration of dissolved oxygen in treated effluent
- The amount of oxygen consumed by microorganisms when decomposing organic matter in water (Correct answer)
- The chemical oxygen required to oxidize all organic and inorganic matter in a sample
- The oxygen demand created by nitrogen compounds during nitrification
Correct answer: The amount of oxygen consumed by microorganisms when decomposing organic matter in water
BOD measures the oxygen consumed by microorganisms as they biologically degrade organic matter in water over a standard 5-day incubation period (BOD5) at 20°C.
Question 3: What is the primary treatment objective of coagulation and flocculation in a drinking water treatment plant?
- To disinfect water by killing pathogenic bacteria
- To aggregate suspended particles and colloids into larger settleable masses (Correct answer)
- To remove dissolved organic compounds through adsorption
- To adjust pH before chlorination
Correct answer: To aggregate suspended particles and colloids into larger settleable masses
Coagulation (chemical destabilization) and flocculation (gentle mixing to form larger aggregates called floc) are the first treatment steps that convert fine suspended particles into settleable masses for removal by sedimentation.
Question 4: Which water quality parameter, measured in mg/L as CaCO3, indicates the water's ability to resist changes in pH?
- Hardness
- Alkalinity (Correct answer)
- Total Dissolved Solids (TDS)
- Chloride concentration
Correct answer: Alkalinity
Alkalinity measures the water's buffering capacity — primarily due to bicarbonate, carbonate, and hydroxide ions — expressed as mg/L CaCO3 equivalent, which resists acidification.
Question 5: What is the purpose of the National Pollutant Discharge Elimination System (NPDES) permit program under the Clean Water Act?
- To regulate underground injection of waste fluids
- To control point source discharges of pollutants into navigable waters of the United States (Correct answer)
- To establish cleanup standards for contaminated surface water bodies
- To regulate nonpoint source agricultural runoff
Correct answer: To control point source discharges of pollutants into navigable waters of the United States
The NPDES program requires permits for any point source discharge (pipes, outfalls, ditches) of pollutants into waters of the US, setting specific effluent limits and monitoring requirements.
Question 6: In a biological wastewater treatment system using activated sludge, what is the function of the aeration basin?
- To settle and remove biological solids from the treated effluent
- To provide oxygen and contact time for microorganisms to metabolize dissolved organic matter (Correct answer)
- To chemically precipitate phosphorus from the wastewater
- To filter out suspended solids using media filtration
Correct answer: To provide oxygen and contact time for microorganisms to metabolize dissolved organic matter
The aeration basin supplies oxygen to a mixed liquor of wastewater and microorganisms (activated sludge), allowing aerobic bacteria to metabolize dissolved and colloidal organic pollutants.
ETC Water Quality & Treatment 1
Which federal law establishes Maximum Contaminant Levels (MCLs) for drinking water contaminants and is enforced by the EPA?