AWWA Quality Control Procedures 2 — Questions and Answers
Question 1: Which statistical tool is used to determine if a water treatment process is in a state of statistical control?
- Pareto chart
- Control chart (Correct answer)
- Scatter diagram
- Histogram
Correct answer: Control chart
Control charts plot process measurements over time to detect when a process drifts outside acceptable limits.
Question 2: What is the purpose of a blank sample in water quality analysis?
- To calibrate the instrument
- To detect contamination in reagents or equipment (Correct answer)
- To establish the detection limit
- To verify sample preservation
Correct answer: To detect contamination in reagents or equipment
A blank sample contains no analyte and reveals if reagents, equipment, or procedures are introducing contamination.
Question 3: Under the Safe Drinking Water Act, which agency sets maximum contaminant levels (MCLs) for public water systems?
- AWWA
- CDC
- EPA (Correct answer)
- OSHA
Correct answer: EPA
The U.S. Environmental Protection Agency establishes legally enforceable MCLs under the Safe Drinking Water Act.
Question 4: A water utility collects duplicate samples to assess which component of data quality?
- Accuracy
- Precision (Correct answer)
- Completeness
- Representativeness
Correct answer: Precision
Duplicates measure precision by showing how closely repeated measurements of the same sample agree.
Question 5: What does the term 'method detection limit' (MDL) represent in water quality testing?
- The highest concentration the method can measure
- The minimum concentration reliably distinguished from zero (Correct answer)
- The target reporting level for regulatory compliance
- The concentration that triggers a treatment response
Correct answer: The minimum concentration reliably distinguished from zero
The MDL is the lowest concentration of an analyte that can be detected with 99% confidence that it is above zero.
Question 6: Which type of quality control sample is used to evaluate matrix interference in a water sample?
- Field blank
- Trip blank
- Matrix spike (Correct answer)
- Equipment rinsate
Correct answer: Matrix spike
A matrix spike adds a known amount of analyte to the sample to evaluate whether the sample matrix inhibits or enhances recovery.
Question 7: When a coliform-positive sample is found during routine monitoring, what is the required immediate action under the Total Coliform Rule?
- Issue a boil-water advisory immediately
- Collect repeat samples within 24 hours (Correct answer)
- Shut down the distribution zone
- Notify the media
Correct answer: Collect repeat samples within 24 hours
The Total Coliform Rule requires collecting repeat samples within 24 hours of learning of a positive result to confirm or refute the finding.
AWWA Quality Control Procedures 2
Which statistical tool is used to determine if a water treatment process is in a state of statistical control?