Ohio · Wastewater Treatment · Class II
Ohio Grade 2 Wastewater Treatment Operator Exam
The Ohio Grade 2 wastewater treatment certification is designated Class II and issued by Ohio Environmental Protection Agency (Ohio EPA). Intermediate certification for operators running day-to-day operations at small to mid-size systems.
Applied math is a significant part of the Ohio Class II 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 II |
|---|---|
| Questions | 100 |
| Time limit | 150 minutes |
| Passing score | 70% |
| Difficulty | Intermediate |
| Exam administered by | Association of Boards of Certification (ABC), administered for Ohio EPA |
Prerequisites for Class II
- Grade 1 certification (in most states)
- 1–2 years of operating experience
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
- Process control adjustments
- Applied treatment math
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 II practice questions
Sample questions with full explanations at this level.
Take the practice quiz →Frequently asked questions
- What is the Ohio Grade 2 wastewater treatment certification called?
- In Ohio, the Grade 2 wastewater treatment certification is designated Class II, 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 100 questions with a 150-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 II in Ohio?
- Typical prerequisites: Grade 1 certification (in most states); 1–2 years of operating experience. Exact requirements are set by Ohio Environmental Protection Agency (Ohio EPA).