Wastewater Lab Analyst Practice Test

50 questions of our own on sampling, BOD, solids, pH and quality control, each with its source.

A total suspended solids sample is cooled to 6 °C or less. What is its maximum holding time?

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Unofficial practice questions, not affiliated with Water Professionals International (formerly ABC). Bank checked October 11, 2026.

The real exam, as its owner describes it

To pass
70% right
Questions
100 multiple-choice questions at each of four classes. Class I is the lowest and Class IV the highest.
Job areas, Class I
Collect and preserve samples 17 percent, prepare samples 12, analyze and interpret 24, equipment 14, chemicals and wastes 5, quality control 9, manage laborator
Tests by class
Class I: pH, dissolved oxygen, chlorine residual, temperature, solids, BOD and settleability. Class II adds COD, nitrogen, phosphorus and coliform. Class III ad
Format
Four answer options, closed book. A non-programmable calculator is allowed, and a formula and conversion table goes with the exam.
Time and pass mark
Three hours and 70 percent are what the exam owner states for its own certification. A state or province that uses the exam sets its own.
The ABC name
The owner was the Association of Boards of Certification (ABC) and is now Water Professionals International. This exam still carries the ABC name.

Checked October 11, 2026 against Water Professionals International's Need-to-Know Criteria for the ABC Wastewater Laboratory Analyst exam and its certification pages. Rules change, so confirm with the agency itself before your test.

The exam owner's Need-to-Know Criteria

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All 50 questions

Collect and Preserve Samples 9

  • A 2-liter flow-based composite is built from 24 grabs, one an hour. The day's flow was 3.2 million gallons, and 160,000 gallons passed in the 2 PM hour. How much of the 2 PM grab goes in? Pennsylvania DEP wastewater operator training, Module 12: Laboratory Overview, Unit 3, Composite Samples; our arithmetic
  • A sample result is challenged. Which record shows who had the sample from collection to the reported result? Pennsylvania DEP wastewater operator training, Module 12: Laboratory Overview, Unit 5, Chain of Custody
  • A total suspended solids sample is cooled to 6 °C or less. What is its maximum holding time? 40 CFR 136.3(e), Table II, residue, nonfilterable (TSS)
  • An ammonia sample will not be run today. How does Table II say to preserve it? 40 CFR 136.3(e), Table II, ammonia
  • By when must incubation of an effluent fecal coliform sample begin? 40 CFR 136.3(e), Table II, coliform, total, fecal and E. coli, with footnote 22
  • How soon after collection must a pH sample be analyzed? 40 CFR 136.3(e), Table II, hydrogen ion (pH)
  • The sterile bottle for a chlorinated effluent coliform sample holds sodium thiosulfate. What does it do? 40 CFR 136.3(e), Table II, bacterial tests, with footnote 5; Pennsylvania DEP wastewater operator training, Module 12: Laboratory Overview, Unit 4, Total Residual Chlorine
  • What is the longest an effluent BOD sample, kept at 6 °C or colder, may be held before the test is started? 40 CFR 136.3(e), Table II, biochemical oxygen demand
  • Which effluent test must be run on a grab sample, never on a composite? Pennsylvania DEP wastewater operator training, Module 12: Laboratory Overview, Unit 3, Grab Samples
Show all 50 questions (41 more)

Prepare Samples for Analysis 6

  • 10 mL of sample is diluted to 100 mL with distilled water. The diluted sample reads 4.2 mg/L. What is the concentration of the original sample? Pennsylvania DEP wastewater operator training, Module 12: Laboratory Overview, Unit 1, Sample Preparation, Dilution; our arithmetic
  • 25 g of a dry reagent is dissolved in 475 g of water. What is the solution's percent by weight? Pennsylvania DEP operator training, Module 29: General Chemistry (2013), Unit 3, Percent by Weight; our arithmetic
  • A grab sample is collected for dissolved orthophosphate. What must be done to it within 15 minutes? 40 CFR 136.3(e), Table II, orthophosphate, with footnote 24
  • In the ammonia procedures, which step comes before the titration, the color reading or the electrode reading? Pennsylvania DEP wastewater operator training, Module 12: Laboratory Overview, Unit 4, Ammonia
  • Which glassware holds one very precise volume and is used to prepare standard solutions? Pennsylvania DEP wastewater operator training, Module 12: Laboratory Overview, Unit 1, Glassware
  • Why is a total phosphorus sample digested before the color is developed? Pennsylvania DEP wastewater operator training, Module 12: Laboratory Overview, Unit 4, Phosphate

Analyze Samples and Interpret Results 12

  • 30 mL of sample goes into a 300 mL BOD bottle with dilution water. Dissolved oxygen is 8.4 mg/L at the start and 4.1 mg/L after 5 days. What is the BOD, with no seed correction? Pennsylvania DEP wastewater operator training, Module 12: Laboratory Overview, Unit 4, Biochemical Oxygen Demand; our arithmetic
  • The 30-day average BOD5 is 240 mg/L in the influent and 30 mg/L in the effluent. What is the percent removal, and does it meet the secondary treatment minimum? 40 CFR 133.102(a)(3), secondary treatment, and 133.101(j), percent removal; our arithmetic
  • A chlorinated effluent sample is seeded with microorganisms for the BOD test. What is done with the seed's own BOD? Pennsylvania DEP wastewater operator training, Module 12: Laboratory Overview, Unit 4, Biochemical Oxygen Demand
  • A glass fiber filter weighs 0.1250 g. After 50 mL of sample is drawn through it and it is dried, it weighs 0.1294 g. What is the total suspended solids? Pennsylvania DEP wastewater operator training, Module 12: Laboratory Overview, Unit 4, Total Suspended Solids; our arithmetic
  • After the total solids test, the dish is ignited at 550 °C. What does the weight lost stand for? Pennsylvania DEP wastewater operator training, Module 12: Laboratory Overview, Unit 4, Total Solids (Volatile and Fixed)
  • At what temperature is a fecal coliform membrane filter incubated? Pennsylvania DEP wastewater operator training, Module 12: Laboratory Overview, Unit 4, Microbiological Procedures
  • At what temperature is a total suspended solids filter dried before it is weighed? Pennsylvania DEP wastewater operator training, Module 12: Laboratory Overview, Unit 4, Solids
  • Effluent total suspended solids average 12 mg/L and the flow is 2.5 MGD. What loading goes on the monitoring report, in pounds per day? Pennsylvania DEP wastewater operator training, Module 12: Laboratory Overview, Unit 6, Discharge Monitoring Reports; 8.34 lb/gal from Module 29, Unit 1; our arithmetic
  • Four dilutions of one sample start at 8.5 mg/L dissolved oxygen. After 5 days they read as below. Which reading belongs to a valid BOD dilution? Pennsylvania DEP wastewater operator training, Module 12: Laboratory Overview, Unit 4, Biochemical Oxygen Demand
  • How is a BOD bottle incubated between the first and the final dissolved oxygen reading? Pennsylvania DEP wastewater operator training, Module 12: Laboratory Overview, Unit 4, Biochemical Oxygen Demand
  • In the settleable solids test, how long does the 1-liter sample settle, and how is the result recorded? Pennsylvania DEP wastewater operator training, Module 12: Laboratory Overview, Unit 4, Settleable Solids
  • Three fecal coliform results in one month are 10, 100 and 1,000 per 100 mL. What is their geometric mean? Pennsylvania DEP wastewater operator training, Module 12: Laboratory Overview, Unit 6, Data Manipulation; our arithmetic

Operate and Maintain Equipment and Instruments 7

  • A graduated cylinder is marked TD. What is it calibrated to measure? Pennsylvania DEP wastewater operator training, Module 12: Laboratory Overview, Unit 1, Glassware
  • A spectrophotometer arrived calibrated by its maker. What does good practice still call for? Pennsylvania DEP wastewater operator training, Module 12: Laboratory Overview, Unit 1, Laboratory Terms, Analytical
  • How does a colorimeter differ from a spectrophotometer? Pennsylvania DEP wastewater operator training, Module 12: Laboratory Overview, Unit 1, Sample Analysis, Spectrophotometric
  • What is a pH meter calibrated with? Pennsylvania DEP wastewater operator training, Module 12: Laboratory Overview, Unit 4, pH
  • Which glassware has a stopcock at the bottom, so a standard solution can be added in very small, measured amounts? Pennsylvania DEP wastewater operator training, Module 12: Laboratory Overview, Unit 1, Glassware
  • Which instrument finds the end point of a chlorine residual titration electrically, not by a color change? Pennsylvania DEP wastewater operator training, Module 12: Laboratory Overview, Unit 1, Analytical Equipment, and Unit 4, Total Residual Chlorine
  • Which rule applies to the refrigerator that holds samples? Pennsylvania DEP wastewater operator training, Module 12: Laboratory Overview, Unit 1, Preparatory Equipment, Refrigerator

Handle Chemicals and Wastes 2

  • A reagent is prepared in the lab and poured into a storage bottle. What belongs on the label? Pennsylvania DEP wastewater operator training, Module 12: Laboratory Overview, Unit 2, Lab Safety
  • Which storage plan follows the rules for laboratory chemicals? Pennsylvania DEP wastewater operator training, Module 12: Laboratory Overview, Unit 2, Lab Safety

Quality Assurance and Quality Control 5

  • A reagent blank shows a measurable amount of the analyte. What does that tell the analyst? Pennsylvania DEP wastewater operator training, Module 12: Laboratory Overview, Unit 5, Quality Control, Blanks
  • A report gives a result as <0.5 mg/L, where 0.5 mg/L is the method detection limit. What does that mean? Pennsylvania DEP wastewater operator training, Module 12: Laboratory Overview, Unit 6, Method Detection Limits
  • A sample reads 2.0 mg/L. A spike of 5.0 mg/L is added and the sample reads 6.5 mg/L. What is the percent recovery? Pennsylvania DEP wastewater operator training, Module 12: Laboratory Overview, Unit 5, Quality Control, Spikes; our arithmetic
  • An outside agency sends a sample whose concentration it knows and the lab does not. What is this sample called? Pennsylvania DEP wastewater operator training, Module 12: Laboratory Overview, Unit 5, Quality Control, Blinds
  • Which of these is one of the twelve quality control elements that 40 CFR 136.7 lists for a method with no QA/QC of its own? 40 CFR 136.7(c)(1), quality assurance and quality control

Manage Laboratory 2

  • An analyst writes a wrong number on a bench sheet. How is it corrected? Pennsylvania DEP wastewater operator training, Module 12: Laboratory Overview, Unit 6, Laboratory Records
  • Under the standard NPDES permit conditions, how long are effluent monitoring records, with their calibration and maintenance records, kept at least? 40 CFR 122.41(j)(2), monitoring and records

Laboratory Safety 5

  • Concentrated acid has to be diluted. Which order is safe? Pennsylvania DEP wastewater operator training, Module 12: Laboratory Overview, Unit 2, Lab Safety
  • How often must an employer review and evaluate its Chemical Hygiene Plan? 29 CFR 1910.1450(e)(4), chemical hygiene plan
  • Where is a chemical that gives off noxious fumes handled? Pennsylvania DEP wastewater operator training, Module 12: Laboratory Overview, Unit 2, Accident Prevention, Toxic Fumes
  • Which person must a Chemical Hygiene Plan designate? 29 CFR 1910.1450(e)(3)(vii), with the definition in 1910.1450(b)
  • Why is pipetting by mouth forbidden in a wastewater laboratory? Pennsylvania DEP wastewater operator training, Module 12: Laboratory Overview, Unit 2, Laboratory Hazards, Infectious Wastes

General Science 2

  • How much more acidic is water at pH 5 than water at pH 7? Pennsylvania DEP operator training, Module 29: General Chemistry (2013), Unit 4, pH Scale
  • Sodium has an atomic weight of 22.99, oxygen 16.00 and hydrogen 1.008. Sodium hydroxide, NaOH, has what molecular weight? Pennsylvania DEP operator training, Module 29: General Chemistry (2013), Unit 2, Molecular Weight and Moles; our arithmetic

How this list was compiled: Our own questions, in the nine job areas and the Class I shares of the Need-to-Know Criteria for the ABC Wastewater Laboratory Analyst exam (Water Professionals International, reprinted February 2024, linked from https://gowpi.org/services/abc-testing/need-to-know-criteria/). Facts were read in 40 CFR 136.3 (Table II), 136.7, 133.101, 133.102 and 122.41 and in 29 CFR 1910.1450 on ecfr.gov, and in two operator training workbooks of the Pennsylvania Department of Environmental Protection, Wastewater Module 12: Laboratory Overview and Module 29: General Chemistry (https://files.dep.state.pa.us/Water/BSDW/OperatorCertification/TrainingModules/), all on 2026-10-11. Each question names the section it was written from. Licence: Own work. Every question, answer choice and explanation was written for this site from the public sources named on it. Nothing is taken from the exam, from its owner's sample questions or study guides, from the training workbooks' own exercises, or from another practice test.

How it works

This wastewater lab analyst practice test follows the nine job areas of the ABC Wastewater Laboratory Analyst Class I Need-to-Know Criteria. It is unofficial and not affiliated with, endorsed by or sponsored by Water Professionals International (formerly ABC).

Read the full guide

Holding times come from Table II

Holding times and preservatives here are those of 40 CFR 136.3, Table II: 48 hours for BOD, 7 days for suspended solids, 8 hours for coliform, 28 days for acidified ammonia.

Why Class I asks ammonia and coliform

The outline's Class I task lists reach past the tests a Class I analyst runs. They include collecting ammonia, phosphorus and coliform samples, digestion and distillation, and the coliform analysis, so this bank asks those too.

Where the answers come from

Rule questions cite 40 CFR Part 136, 133 or 122, or the OSHA laboratory standard, by section. Method questions cite Pennsylvania's public operator training modules, because the exam's listed references are commercial books.

  • Learn the 15-minute group together: pH, chlorine residual, temperature and a dissolved oxygen probe reading cannot be held.
  • A valid BOD dilution uses at least 2 mg/L of oxygen and keeps at least 1 mg/L.
  • Use the outline as your wastewater laboratory certification study guide: mark each test your class lists, then read it up in Module 12.

Questions and answers

Is there a free wastewater lab analyst study guide?

The exam owner's Need-to-Know Criteria is the free outline; the references it lists are commercial books. Pennsylvania's Module 12, Laboratory Overview, is a free public workbook on the Class I tests, and most of these questions are written from it.

Where is the New Mexico wastewater laboratory certification study guide?

The New Mexico Environment Department posts it on its exam preparation page. It is written for the state's Wastewater Laboratory Technician Level 1, 2 and 3 exams. Our questions follow the ABC outline, so read both.

Is this a wastewater laboratory technician study guide too?

For the basic tests, yes. New Mexico's certificate says laboratory technician and the ABC exam says laboratory analyst, and both cover solids, BOD, pH, chlorine residual and coliform. Check your own state's outline for the rest.

How many questions are on the wastewater laboratory analyst exam?

The Need-to-Know Criteria give each of the four classes 100 multiple-choice questions. An exam your state writes for itself may differ, so ask your certifying authority.

What score passes the wastewater laboratory analyst exam?

Water Professionals International asks 70 percent or higher for its own certification. A state or province that uses the exam sets its own pass mark.

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