Administered by State Water Resources Control Board (SWRCB) — Wastewater Operator Certification Program (WWOCP)
The Grade III exam runs 3 h 30 min with 61 items worth 97 points, and passing needs both 70% overall and at least half of the math points.
The certificate for operating a wastewater treatment plant in California, issued through the State Water Resources Control Board's Wastewater Operator Certification Program.
Equivalents and Formulas Sheet, Version 1 (opens in a new tab)State Water Resources Control Board, Wastewater Operator Certification Program · The program has announced that exams will include both sheets.
Equivalents and Formulas Sheet, Version 2 (opens in a new tab)State Water Resources Control Board, Wastewater Operator Certification Program · The program has announced that exams will include both sheets.
Grade III eligibility
Education and experience paths to Grade III
Education
Qualifying experience
High school + 12 educational points
3 years as a Grade II operator
High school + 18 educational points
4 years
Associate degree or 60 units incl. 15 science units
2 years
Bachelor's or higher incl. 30 science units
1 year
The exam is taken before applying for certification; an operator-in-training (OIT) certificate lets a passer accrue the qualifying experience.
Experience is full-time qualifying experience (1,800 hours equals one year for operators-in-training).
Examination results are valid for four years from the date on the pass letter.
New at Grade III: process control, activated sludge process modifications and tertiary treatment; supervision basics.
Math topics at Grade III: thickening efficiency and loading, disinfectant use, digester loading, pumping efficiency, biochemical oxygen demand (BOD), loading rates, wasting rate, mixed liquor suspended solids (MLSS) and mixed liquor volatile suspended solids (MLVSS), sludge pumping, nitrogenous BOD, food-to-microorganism ratio (F/M), polymer use.
How the Grade III exam is built
Item type
Count and points
true/false
25 items at 1 point each
multiple choice
20 items at 2 points each
multiple-choice essay
6 items at 2 points each
math
10 items at 2 points each
Grade III exam format
Items: 61, worth 97 points
Time allowed: 3 h 30 min
Pass score: 68 points (70%) and at least 10 of 20 math points
Computer-based at Prometric centers year-round since February 2021; wastewater applications carry a 60-day filing period before the earliest test date.
Process control: food-to-microorganism ratio (F/M) · an original practice item written only from publicly available sources, not a real exam question
An aeration basin holds 1.2 million gallons (MG) with mixed liquor suspended solids (MLSS) of 3,000 mg/L and mixed liquor volatile suspended solids (MLVSS) of 2,400 mg/L. It receives 4 million gallons per day (MGD) of primary effluent with a biochemical oxygen demand (BOD) of 150 mg/L. What is the F/M ratio on an MLVSS basis?
0.17
0.21
2.08
4.80
Answer and working
B. 0.21
Food = 4 MGD × 150 mg/L × 8.34 = 5,004 lb BOD/day. Microorganisms = 1.2 MG × 2,400 mg/L × 8.34 = 24,019 lb MLVSS. F/M = 5,004 ÷ 24,019 = 0.21 per day. 0.17 uses MLSS instead of MLVSS, 4.80 inverts the ratio, and 2.08 slips the decimal one place.
Grade III questions answered
How is the Grade III wastewater exam structured?
61 items worth 97 points in 3 h 30 min: true/false, 25 items at 1 point each; multiple choice, 20 items at 2 points each; multiple-choice essay, 6 items at 2 points each; math, 10 items at 2 points each. Passing takes 68 points (70%) and at least 10 of 20 math points.
What education and experience does Grade III require?
High school + 12 educational points, with 3 years as a Grade II operator; or high school + 18 educational points, with 4 years; or associate degree or 60 units incl. 15 science units, with 2 years; or bachelor's or higher incl. 30 science units, with 1 year. The exam is taken before applying for certification; an operator-in-training (OIT) certificate lets a passer accrue the qualifying experience.
What is the recent Grade III pass rate?
42%: 148 of 355 examinees passed from July 1, 2025 to June 30, 2026, summed from the agency's two half-year results tables.
What this exam covers
Preliminary & Primary
Activated Sludge
Secondary Clarification
Nutrient Removal
Disinfection
Biosolids & Digestion
Regulations & Effluent
Lab & Process Control
Operations & Safety
How to study for it here
Practice quizzes — filter to any topic above and work through it with explanations.
Flashcards — spaced repetition over terms, formulas and regulations.
Mock exam — a timed run at this grade, scored by points with the separate math minimum, as on the real exam.
Official formula sheet — a link to the sheet the certifying body publishes for this exam, where it publishes one, so you study from the real thing.
Free, no account, and progress stays in your browser.
Topic coverage follows WWTP Operator Examination Information (SWRCB Wastewater Operator Certification Program — per-grade documents).
Practice questions are written only from publicly available sources
(that outline and the regulations and references it cites); they are
not real exam questions, which are confidential.
Check current application requirements, fees and exam dates on the
certifying body's own page: official certification page.
Questions, flashcards, and explanations are AI-written from publicly available sources only: the exam content outlines and candidate materials each certifying body publishes without restriction, and the regulations and technical references they cite. No confidential material is used, including actual exam questions, recollections of any exam sat by the author, or any handbook or document released under a confidentiality agreement. Content is then put through repeated review — regulatory values checked against primary sources, every calculation recomputed, and errors corrected — plus spot checks by the author, who holds California water operator certifications and a California civil engineering licence. Those spot checks are sampling, not a professional review: nothing here is stamped, sealed, or offered as engineering advice, and not every item has been individually verified, so mistakes can still slip through.