California · Wastewater Treatment · Grade IV
California Grade 4 Wastewater Treatment Operator Exam
The California Grade 4 wastewater treatment certification is designated Grade IV and issued by State Water Resources Control Board, Division of Drinking Water (water); Office of Operator Certification (wastewater). Highest certification for chief operators and superintendents at the largest, most complex systems.
Applied math is a significant part of the California Grade IV exam.
Practicing calculations like dosage, detention time, and loading before test day is one of the most effective ways to prepare, alongside reviewing your state’s official exam content outline.
Exam facts
| Grade level | Grade IV |
|---|---|
| Questions | 120 |
| Time limit | 210 minutes |
| Passing score | 70% |
| Difficulty | Expert |
| Exam administered by | State Water Resources Control Board (in-house exams) |
Prerequisites for Grade IV
- Grade 3 certification
- 4+ years of operating experience including supervisory time
- College coursework or degree (varies by state)
Confirm exact requirements with State Water Resources Control Board, Division of Drinking Water (water); Office of Operator Certification (wastewater).
What's on the exam
- Preliminary and primary treatment
- Activated sludge process control
- Secondary clarification
- Nutrient removal (nitrogen, phosphorus)
- Disinfection and dechlorination
- Solids handling and biosolids
- Plant-wide optimization
- Management, budgeting, and staffing
The math on the Wastewater Treatment exam
These calculations are commonly included in wastewater treatment operator exam preparation and may appear on your exam depending on your certification level and state. Practicing them is one of the most effective ways to prepare.
- Food-to-microorganism (F:M) ratio
- Mean cell residence time (MCRT/SRT)
- Sludge volume index (SVI)
- Hydraulic and organic loading
- Detention time
- Pounds formula (lbs/day)
Free Grade IV practice questions
Sample questions with full explanations at this level.
Take the practice quiz →Frequently asked questions
- What is the California Grade 4 wastewater treatment certification called?
- In California, the Grade 4 wastewater treatment certification is designated Grade IV, issued by State Water Resources Control Board, Division of Drinking Water (water); Office of Operator Certification (wastewater).
- How many questions are on the exam and what score do I need?
- The exam has about 120 questions with a 210-minute time limit, and you need 70% to pass. It is administered by State Water Resources Control Board (in-house exams).
- What are the prerequisites for Grade IV in California?
- Typical prerequisites: Grade 3 certification; 4+ years of operating experience including supervisory time; College coursework or degree (varies by state). Exact requirements are set by State Water Resources Control Board, Division of Drinking Water (water); Office of Operator Certification (wastewater).