ABC Field Test and Inspection Procedures 3 — Questions and Answers
Question 1: When performing a coliform sample from a new water main before placing it into service, how many consecutive satisfactory samples are typically required by US regulations?
- 1
- 2 (Correct answer)
- 3
- 5
Correct answer: 2
The Total Coliform Rule generally requires two consecutive satisfactory bacteriological samples before a new main is approved for service.
Question 2: Which test is performed in the field to quickly estimate the biological oxygen demand (BOD) trend without laboratory incubation?
- COD rapid test (Correct answer)
- Dissolved oxygen deficit measurement
- Respirometry
- Ammonia colorimetric test
Correct answer: COD rapid test
Chemical Oxygen Demand (COD) is a rapid surrogate that correlates to BOD and can be completed with field test kits.
Question 3: An operator notices the turbidity of filtered water has increased from 0.1 NTU to 0.45 NTU. Under the Surface Water Treatment Rule, the regulatory action level is:
- 0.3 NTU as a daily maximum
- 1 NTU as a running annual average
- 0.3 NTU in 95% of samples per month (Correct answer)
- 0.5 NTU as an instantaneous maximum
Correct answer: 0.3 NTU in 95% of samples per month
SWTR requires filtered water turbidity to be ≤0.3 NTU in 95% of monthly measurements for conventional filtration.
Question 4: What is the purpose of performing a chlorine demand test on a water sample?
- To measure free chlorine residual at the tap
- To determine how much chlorine is consumed before a residual remains (Correct answer)
- To detect chloramines in treated water
- To calibrate a colorimeter
Correct answer: To determine how much chlorine is consumed before a residual remains
Chlorine demand is the difference between the chlorine dose applied and the residual remaining after contact time.
Question 5: A wastewater inspector observes foam formation in an activated sludge aeration basin. The MOST likely cause is:
- High dissolved oxygen levels
- Excessive filamentous organism or surfactant presence (Correct answer)
- Low mixed liquor suspended solids (MLSS)
- High influent pH
Correct answer: Excessive filamentous organism or surfactant presence
Persistent foam in aeration basins is commonly caused by filamentous bacteria (e.g., Nocardia) or surfactants in the influent.
Question 6: Which container material is required when collecting samples for volatile organic compound (VOC) analysis?
- Plastic HDPE bottle with preservative
- 40 mL glass vial with Teflon-lined septum cap, no headspace (Correct answer)
- 1 L amber glass bottle with ice
- Sterile plastic bag
Correct answer: 40 mL glass vial with Teflon-lined septum cap, no headspace
VOC samples must be collected in 40 mL vials with no headspace to prevent volatilization losses during transport.
Question 7: What field inspection step verifies the integrity of a water storage tank's roof vent?
- Checking the pressure relief valve setting
- Inspecting the screened vent for blockage and intact mesh (Correct answer)
- Measuring the tank water level with a transducer
- Testing the overflow pipe for backflow prevention
Correct answer: Inspecting the screened vent for blockage and intact mesh
Roof vents must be screened to prevent insects, birds, and debris from entering the tank; blocked vents create pressure problems.
ABC Field Test and Inspection Procedures 3
When performing a coliform sample from a new water main before placing it into service, how many consecutive satisfactory samples are typically required by US regulations?