CH Water Quality & Management 3 — Questions and Answers
Question 1: A Total Maximum Daily Load (TMDL) allocates pollutant loads among which sources?
- Point sources, nonpoint sources, and a margin of safety (Correct answer)
- Only permitted industrial dischargers
- Atmospheric deposition only
- Groundwater contributions only
Correct answer: Point sources, nonpoint sources, and a margin of safety
A TMDL divides the allowable pollutant load among wasteload allocations (point sources), load allocations (nonpoint sources), and a margin of safety.
Question 2: Which sampling method is preferred for collecting water quality samples to represent average stream conditions at a cross-section?
- Depth-integrated sampling across the stream width (Correct answer)
- Surface grab sample at the thalweg
- Single-point midstream sample
- Nearshore bank sample
Correct answer: Depth-integrated sampling across the stream width
Depth-integrated samples collected at multiple verticals across the cross-section provide a flow-weighted composite representative of total stream conditions.
Question 3: The US EPA's National Pollutant Discharge Elimination System (NPDES) regulates which type of water pollution source?
- Point source discharges to navigable waters (Correct answer)
- Agricultural nonpoint source runoff
- Atmospheric dry deposition
- Groundwater infiltration
Correct answer: Point source discharges to navigable waters
NPDES permits regulate point source discharges—those from a discrete conveyance such as a pipe or ditch—to waters of the US.
Question 4: Which process most effectively removes phosphorus from stormwater in a constructed wetland?
- Sedimentation and biological uptake by vegetation (Correct answer)
- Volatilization
- Photolysis
- Ion exchange with atmospheric gases
Correct answer: Sedimentation and biological uptake by vegetation
Phosphorus is removed in wetlands primarily through particle settling and assimilation by aquatic plants and algae.
Question 5: A stream's assimilative capacity refers to its ability to:
- Receive and break down pollutants without violating water quality standards (Correct answer)
- Transport sediment during flood events
- Generate dissolved oxygen through photosynthesis
- Recharge underlying aquifers
Correct answer: Receive and break down pollutants without violating water quality standards
Assimilative capacity is the amount of waste a water body can absorb through natural processes without exceeding water quality criteria.
Question 6: Which parameter is the best indicator of fecal contamination from warm-blooded animals in recreational waters?
- Escherichia coli (E. coli) or Enterococcus bacteria (Correct answer)
- Total suspended solids
- Turbidity
- Chlorophyll-a
Correct answer: Escherichia coli (E. coli) or Enterococcus bacteria
E. coli and Enterococcus are fecal indicator bacteria used by the EPA to assess microbial water quality for recreational standards.
Question 7: When collecting water samples for volatile organic compound (VOC) analysis, the sample bottle should be:
- Filled completely with no headspace and kept chilled (Correct answer)
- Collected in an amber glass bottle open to air
- Stored at room temperature for 24 hours
- Preserved with excess sulfuric acid
Correct answer: Filled completely with no headspace and kept chilled
VOCs escape to headspace readily, so bottles must be completely filled, zero-headspace preserved, and chilled to minimize volatilization losses.
CH Water Quality & Management 3
A Total Maximum Daily Load (TMDL) allocates pollutant loads among which sources?