Ohio · Wastewater Treatment · Class I
Ohio Grade 1 Wastewater Treatment Operator Exam
The Ohio Grade 1 wastewater treatment certification is designated Class I and issued by Ohio Environmental Protection Agency (Ohio EPA). Entry-level certification for operators at small systems or working under direct supervision.
Applied math is a significant part of the Ohio Class I 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 I |
|---|---|
| Questions | 100 |
| Time limit | 120 minutes |
| Passing score | 70% |
| Difficulty | Entry |
| Exam administered by | Association of Boards of Certification (ABC), administered for Ohio EPA |
Prerequisites for Class I
- High school diploma or GED
- 0–1 year of operating experience (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
- Basic operations and monitoring
- Recordkeeping and reporting
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 I practice questions
Sample questions with full explanations at this level.
Take the practice quiz →Frequently asked questions
- What is the Ohio Grade 1 wastewater treatment certification called?
- In Ohio, the Grade 1 wastewater treatment certification is designated Class I, 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 120-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 I in Ohio?
- Typical prerequisites: High school diploma or GED; 0–1 year of operating experience (varies by state). Exact requirements are set by Ohio Environmental Protection Agency (Ohio EPA).