Ohio · Wastewater Treatment · Class IV
Ohio Grade 4 Wastewater Treatment Operator Exam
The Ohio Grade 4 wastewater treatment certification is designated Class IV and issued by Ohio Environmental Protection Agency (Ohio EPA). Highest certification for chief operators and superintendents at the largest, most complex systems.
Applied math is a significant part of the Ohio Class 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 | Class IV |
|---|---|
| Questions | 120 |
| Time limit | 210 minutes |
| Passing score | 70% |
| Difficulty | Expert |
| Exam administered by | Association of Boards of Certification (ABC), administered for Ohio EPA |
Prerequisites for Class IV
- Grade 3 certification
- 4+ years of operating experience including supervisory time
- College coursework or degree (varies by state)
Confirm exact requirements with Ohio Environmental Protection Agency (Ohio EPA).
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 Class IV practice questions
Sample questions with full explanations at this level.
Take the practice quiz →Frequently asked questions
- What is the Ohio Grade 4 wastewater treatment certification called?
- In Ohio, the Grade 4 wastewater treatment certification is designated Class IV, issued by Ohio Environmental Protection Agency (Ohio EPA).
- 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 Association of Boards of Certification (ABC), administered for Ohio EPA.
- What are the prerequisites for Class IV in Ohio?
- 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 Ohio Environmental Protection Agency (Ohio EPA).