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CA-NV AWWA Water Quality Laboratory Analyst Grade 2 –
Practice Exam 2025/2026 | REAL QUESTIONS WITH
ANSWERS & RATIONALES | PDF FREE
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Question 1
What is the primary purpose of the California Title 22 regulations regarding water quality laboratories? Answer: B A) To set drinking water fees B) To establish certification requirements for laboratories analyzing drinking water C) To mandate pipe materials D) To regulate well drilling
Question 2
Under Nevada Administrative Code (NAC 445A), how often must a certified water quality laboratory participate in proficiency testing (PT) for each accredited analyte? Answer: C A) Annually B) Every 6 months C) Twice per year (semi-annually) D) Quarterly
Explanation: NAC 445A.870 requires laboratories to demonstrate continued competency through proficiency testing at least twice per year (semi-annually) for each analyte and method for which certification is held.
Question 3
The Method Detection Limit (MDL) is defined as: Answer: B A) The lowest concentration that can be reported with 100% accuracy B) The minimum concentration that can be measured with 99% confidence that it is above zero C) The average of seven replicate blanks D) The concentration equal to the instrument noise floor Explanation: The MDL is statistically defined as 3.14 times the standard deviation of seven or more replicate low-concentration samples analyzed through the entire method, providing 99% confidence that the analyte is present above zero (40 CFR Part 136 Appendix B).
Question 4
A laboratory runs a coliform test and observes a positive result on the presumptive test but negative on the confirmed test. How should this be reported? Answer: A A) Negative for total coliforms B) Positive for total coliforms C) Presumptive positive only D) Recollect and retest
Question 7
The quality control limit for a laboratory control sample (LCS) for a volatile organic compound (VOC) analysis by GC/MS is typically: Answer: B A) 50 – 150% recovery B) 70 – 130% recovery (per method-specific criteria) C) 90 – 110% recovery D) 100% recovery ±5%
Question 8
In Nevada, what is the maximum contaminant level (MCL) for total arsenic in drinking water? Answer: C A) 50 μg/L B) 5 μg/L C) 10 μg/L D) 25 μg/L Explanation: Both Nevada and California follow the federal MCL for arsenic of 10 μg/L (0.010 mg/L) under the Safe Drinking Water Act. California has a slightly lower public health goal (0.0004 μg/L) but the MCL remains 10 μg/L.
Question 9
When performing a heterotrophic plate count (HPC) by spread plate method, what is the acceptable colony count range for reporting? Answer: D
A) 0 – 100 CFU/mL B) 20 – 200 CFU/mL C) 30 – 300 CFU/mL D) 25 – 250 CFU/mL (or per method — typically 30–300 for pour plate, 25–250 for spread plate)
Question 10
What does a "false positive" mean in coliform testing? Answer: A A) The test indicates coliforms are present when they are actually absent B) The test indicates no coliforms when they are present C) The sample was collected improperly D) The incubator temperature was too low
Question 11
A pH meter must be calibrated using at least how many buffer solutions that bracket the expected sample pH? Answer: B A) One buffer B) Two buffers (e.g., 4.0 and 7.0 or 7.0 and 10.0) C) Three buffers D) Five buffers
Question 14
For a laboratory to be certified in California for drinking water analysis, what accreditation body must approve the lab? Answer: B A) US EPA B) California ELAP (Environmental Laboratory Accreditation Program) C) ISO 17025 alone D) NELAC alone
Question 1 5
What is the purpose of a matrix spike (MS) and matrix spike duplicate (MSD)? Answer: C A) To check calibration B) To check the instrument sensitivity C) To evaluate bias and precision in a specific sample matrix D) To sterilize the sample
Question 16
The holding time for a total organic carbon (TOC) sample is: Answer: B A) 14 days B) 28 days (if preserved with H3PO4 to pH <2 and stored at 4°C)
C) 48 hours D) 7 days
Question 17
A laboratory analyst runs a reagent blank and finds a detectable level of the target analyte. What is the most appropriate action? Answer: D A) Ignore it because it is small B) Subtract the blank from all samples C) Report all samples as positive D) Investigate the source of contamination (reagents, glassware, water, etc.) and re- analyze the batch
Question 18
Which statistical measure is used to calculate the relative percent difference (RPD) between duplicate samples? Answer: A A) (Difference between duplicates) / (Average of duplicates) × 100 B) Standard deviation divided by mean × 100 C) (High – Low) / High × 100 D) (Sum of duplicates) / 2 Explanation: RPD = |D1 – D2| / ((D1 + D2)/2) × 100. It measures precision between two measurements.
The term "LOD" (Limit of Detection) is best defined as: Answer: D A) The same as the MDL B) The lowest concentration that can be quantified with precision C) The concentration equal to 10 times the standard deviation of blanks D) The lowest concentration that can be reliably distinguished from a blank (not necessarily quantified)
Question 22
When analyzing a drinking water sample for lead by graphite furnace AA, which quality control sample is most critical for detecting matrix interference? Answer: B A) Calibration blank B) Matrix spike C) Laboratory control sample D) Continuing calibration verification
Question 23
What is the acceptable temperature range for incubation of total coliform samples using the membrane filtration method (mEndo agar)? Answer: A
A) 35°C ± 0.5°C
B) 44.5°C ± 0.2°C
C) 37°C ± 1°C
D) 25°C ± 2°C
Question 24
A laboratory reports a result of "<0.5 μg/L" for a volatile organic compound. The MDL for the method is 0.2 μg/L and the LOQ is 0.5 μg/L. Is the reporting correct? Answer: B A) Yes, because it is below the LOQ B) No, because results below the LOQ but above the MDL should be reported as the estimated value (e.g., "0.3 J" or "0.3 μg/L E") C) Yes, always D) No, it should be reported as 0.
Question 25
Which of the following parameters has the shortest holding time? Answer: C A) Nitrate (28 days preserved) B) TOC (28 days preserved) C) Coliform (8 hours unless chilled to 4°C, then 30 hours) D) Lead (6 months with nitric acid)
A laboratory receives a sample for alkalinity analysis. What is the maximum holding time? Answer: A A) 14 days (if refrigerated) B) 48 hours C) 24 hours D) No limit
Question 29
What is the concentration of the total coliform positive control recommended in Standard Methods? Answer: C A) 1 – 10 CFU/mL B) 10 – 100 CFU/mL C) 10 – 300 CFU per test (e.g., 10–300 colonies on MF or positive in multiple tubes) D) 1000 – 5000 CFU/mL Explanation: Positive controls should produce clearly positive results without overloading the test; 10–300 CFU/100 mL is typical for membrane filtration.
Question 30
A turbidimeter must be calibrated using: Answer: D A) Distilled water only B) A single standard C) Formazin primary standards
D) At least two primary standards (e.g., 0.1 NTU and 10 NTU) that bracket the expected range Explanation: Standard Methods 2130B requires a multi-point calibration using primary formazin standards to ensure linearity across the measurement range.
Question 31
Which of the following indicates a laboratory is compliant with the "method blank" acceptance criteria for volatile organics? Answer: B A) Method blank is below the MDL B) Method blank is below the reporting limit (LOQ) or method-specified blank limit C) Method blank is below 5 μg/L D) Method blank is zero
Question 32
What is the required quality control frequency for a duplicate analysis in a CA drinking water lab? Answer: C A) 1 per 100 samples B) 1 per 50 samples C) 1 per 20 samples (minimum 5% of samples) D) 1 per 5 samples
C) Appropriate training and documented competency for each method they perform D) A professional engineering license Explanation: Title 22 requires documented initial training, annual proficiency demonstration, and method-specific competency for each analyst.
Question 36
What is the primary purpose of a "laboratory control sample" (LCS)? Answer: B A) To check the sampling technique B) To assess method accuracy by analyzing a known concentration of analyte in clean matrix C) To determine the MDL D) To check the field preservatives
Question 37
When reporting lead results under California's Copper and Lead Rule, the action level is: Answer: A A) 15 μg/L (lead); 1.3 mg/L (copper) B) 10 μg/L (lead); 0.5 mg/L (copper) C) 50 μg/L (lead); 5 mg/L (copper) D) 5 μg/L (lead); 0.1 mg/L (copper) Explanation: Federal and CA action levels for lead are 15 μg/L (0.015 mg/L) at the 90th percentile of customer taps.
Question 38
A laboratory is running a batch of 30 samples for fluoride by ion selective electrode. How many quality control samples are minimally required? Answer: B A) 1 blank, 1 LCS B) 1 blank, 1 LCS, 1 duplicate, and 1 matrix spike (or every 20 samples) C) No QC required D) Only calibration standards
Question 39
What is the maximum allowable residual chlorine level in drinking water as it leaves the treatment plant in California? Answer: D A) 0.5 mg/L B) 1.0 mg/L C) 2.0 mg/L D) 4.0 mg/L (as Cl2) (MRDL) Explanation: EPA and CA have a Maximum Residual Disinfectant Level (MRDL) of 4. mg/L for chlorine.
Question 40
A sample for trihalomethanes (THMs) must be preserved with: Answer: C A) Sulfuric acid B) Sodium thiosulfate only
Question 43
Which of the following is NOT a required element of a Chain of Custody (COC) form? Answer: D A) Sample ID and date/time of collection B) Signatures of each person handling the sample C) Preservatives used D) The cost of analysis
Question 44
When analyzing a sample for total dissolved solids (TDS), the residue is dried at: Answer: B A) 105°C B) 180°C ± 2°C (per Standard Methods 2540C) C) 550°C D) 60°C
Question 45
A laboratory obtains a recovery of 140% on a laboratory control sample for a volatile organic compound with an acceptance limit of 70–130%. What should the analyst do? Answer: C A) Report the batch as is B) Subtract 40% from all samples
C) Flag the batch as out-of-control, investigate cause (e.g., contamination or calibration), and reanalyze D) Change the acceptance limits
Question 46
Which of the following is an acceptable method for determining residual chlorine in the field? Answer: A A) DPD colorimetric method B) Gravimetric analysis C) Ion chromatography D) Atomic absorption
Question 47
What is the holding time for a sample collected for asbestos analysis (drinking water) by TEM? Answer: B A) 7 days B) 14 days (if preserved with chlorine removal and stored at 4°C) C) 48 hours D) 6 months
