Median Pay by Area
- Chicago-Naperville-Elgin, IL-IN
- $79,290 a year
- Bloomington
- $79,220 a year
- Rockford
- $77,830 a year
- Champaign-Urbana
- $61,720 a year
- Peoria
- $60,380 a year
- Springfield
- $58,990 a year
- South Illinois nonmetropolitan area
- $56,080 a year
Illinois wastewater operators
The steps from no certificate to an Illinois wastewater operator certificate, how to qualify for and pass the exam, how to keep your certificate active and what operators earn. Every requirement links to the Illinois Environmental Protection Agency (Illinois EPA) Wastewater Operator Certification program or its rule, 35 Ill. Adm. Code Part 380.
Illinois EPA makes the final eligibility determination. Check with Illinois EPA before you apply.
Why it matters
Illinois's wastewater operator certification program is mandatory. Every wastewater treatment plant in Illinois must be run by an operator certified at or above the level the plant requires.
Every wastewater treatment or pretreatment works that needs a permit under 35 Ill. Adm. Code 309 (such as an NPDES or operating permit) must have a Chief Wastewater Operator on its staff, named to Illinois EPA in writing. The Chief Wastewater Operator holds the required class of certificate, directly supervises the plant, is responsible for process control decisions and submits the required reports.
Instead of hiring, a plant may contract with a certified operator or a contract operations firm. Illinois EPA must approve the contract.
Collection system certification is voluntary: a certified collection system operator is not required to run a collection system, although Illinois EPA strongly recommends it and a permit may require one.
In Illinois, a wastewater operator is someone who regularly makes recommendations or is responsible for process control decisions at a treatment plant. The term does not cover people whose duties are only lab testing or maintenance.
Illinois has four municipal certificates, from Class 4 (the lowest) to Class 1 (the highest), plus a Collection System Operator certificate and two industrial certificates, Class K and Class R.
Each municipal plant is put in a group by its type of treatment and design average flow (DAF). Group 4 is lagoon systems and septic tank systems permitted by Illinois EPA. Group 3 is fixed film processes (such as trickling filters and rotating biological contactors), recirculating sand filters and Imhoff tanks under 1.0 MGD, plus all primary treatment systems. Group 2 is activated sludge systems under 1.0 MGD. Group 1 is every plant of 1.0 MGD or more, except lagoon and primary treatment systems.
The plant's group sets the certificate its Chief Wastewater Operator needs: Class 1 for Group 1, Class 2 or higher for Group 2, Class 3 or higher for Group 3 and Class 4 or higher for Group 4. A plant with more than one process is grouped by its more complex process.
Industrial plants need a Class K certificate, which is only valid at the one plant it was issued for. Class R covers plants that treat surface water or groundwater contaminated by gasoline, diesel fuel, kerosene, jet fuel or heating oil. A municipal certificate such as Class 1 does not let you run an industrial plant.
Step 1
Every Class 1 to 4 certificate needs a high school diploma or GED, the ability to read and write English, and years of wastewater operator experience: 1 year for Class 4, 2 for Class 3, 4 for Class 2 and 6 for Class 1.
At least half of that must be hands-on experience at a municipal wastewater treatment plant: running treatment equipment or processes, directly supervising them in the field, or taking part in process control decisions. Illinois EPA counts 400 hours of hands-on work as 3 months.
Public works, street maintenance, meter reading, running a Vactor truck, hauling or applying sludge, janitorial work, groundskeeping, collection system or drinking water work, lab testing, and electrical or maintenance work do not count as hands-on wastewater operating experience.
Work at an industrial (Group K or Group R) plant does not count toward a Class 1 to 4 certificate.
Step 2
Once you have the minimum hands-on experience, the rest can come from other credit. Each 30 hours of approved wastewater coursework counts as 3 months, up to 3 months for Class 4, 6 months for Class 3, 1 year for Class 2 and 2 years for Class 1.
For Classes 1 to 3, a college program of a year or more designed for wastewater plant operation, with hands-on operation, can count for up to 1 year, and other college credit for up to 1 more year: 5 semester hours equal one month. For Class 4, college credit counts only through such a wastewater operation program.
Two months of operating a collection system or community water supply, or of lab or maintenance work at a wastewater plant, equal one month of wastewater operator experience. This counts for up to 3 months for Class 4, 6 months for Class 3 and 1 year for Classes 1 and 2.
Full-time work is 30 hours or more a week. Training you use as credit toward a certificate cannot also count toward renewing it.
Step 3
You can take an exam before you have the experience for that class, and you do not have to pass the lower classes first. You must pass the exam for the class you apply for.
Send Illinois EPA the Examination Request for Wastewater Operator Certification at least 30 days before the exam date you want, circling one exam level. Incomplete requests are denied.
Illinois EPA mails you a Letter of Admission, which is good for one exam within one year. Then call or email the testing site you choose to reserve a seat, at least 7 days before the exam. You cannot just walk in.
If you need an accommodation for a disability, say so on the exam request. Illinois EPA must approve it in writing before the exam.
Step 4
When you pass a Class 1 to 4 exam, you become an Operator in Training (OIT) for that class. Your passing score stays valid for 5 years, so you can finish your experience and still use it.
An Operator in Training cannot serve as a plant's properly certified operator.
Once you meet the experience for that class, send Illinois EPA the application for certification (the Municipal Class 1-4 Application). Do not send it until you have passed the exam. Illinois EPA decides within 90 days of a complete application.
Illinois EPA says there are no fees for wastewater operator certification at present.
Tell Illinois EPA in writing within 30 days of any change in your phone number, email or mailing address.
Step 5
Class 1 to 4 certificates last 3 years: each expires 3 years after July 1 of the year it was issued. Illinois EPA sends a notice by April 1 of the year it expires, and your renewal application is due on or before July 1 of that year. Not getting the notice does not change the deadline.
Class 1 and 2 operators need 30 hours of training in each 3-year period, at least 20 on the technical side of wastewater treatment and operations. Class 3 and 4 operators need 15 hours, at least 10 technical. Up to 10 hours (Class 1 and 2) or 5 hours (Class 3 and 4) may cover professional responsibilities and safety.
Training counts only if Illinois EPA approves it, and you need proof of attendance from the training provider. Keep your own proof of training records, and send your record of completed training to Illinois EPA before your certificate expires.
If you miss the deadline, you can have the certificate restored within 2 years of expiring by showing the required training. After 2 years, you must pass the exam and apply again like a new operator.
Collection System Operator certificates do not expire and need no training hours. Class K and R certificates last 5 years and cannot be renewed: you pass the exam again.
Exam day
Illinois EPA gives its own exams. The Class 4, 3, 2 and 1 and Collection System exams each have 100 multiple-choice questions with four answer choices, and you get up to 3 hours. You can take one exam a day.
You pass with 70 percent. Results are mailed to your home, typically within 30 days, with a breakdown of how you did in each subject.
The exams get harder from Class 4 to Class 1. Class 4 stresses lagoons and lagoon math, Class 3 fixed film and intermediate math, Class 2 activated sludge and its math, and Class 1 advanced activated sludge and complex math. About 10 questions on each are math.
You get scratch paper, pencils, an answer sheet and an exam booklet that includes formulas and conversion factors. Bring only your Letter of Admission, a state-issued photo ID and a calculator that is not programmable and cannot store letters. Phones, smart watches and other devices are not allowed.
The 2026 schedule lists monthly exams from 9:00 a.m. to 12:00 p.m. in Des Plaines, Rockford, Springfield (Illinois EPA headquarters) and Marion, and at the Environmental Resources Training Center (ERTC) in Edwardsville.
There is no waiting period to retake a failed exam. After your results arrive, send a new exam request and get a new Letter of Admission.
Illinois EPA gives its own exams: 100 multiple-choice questions for Classes 1 to 4, with the formulas and conversion factors printed in the exam booklet. Operator Master's free practice questions, timed practice exam and math help are built on the WPI exam format and the WPI formula table, not Illinois EPA's exam or formula pages, so use them for general wastewater knowledge and math, and use Illinois EPA's Wastewater Operator Certification Guide as your main guide to what the Illinois exam covers. Operator Master is an independent study tool, not the official exam.
Pay
The median pay for water and wastewater treatment plant and system operators in Illinois was $67,810 a year ($32.60 an hour) in 2025, compared with $60,020 nationally. One in ten earned $42,240 or less, and one in ten earned $103,690 or more.
These federal figures cover drinking water and wastewater operators together, at every class. Pay for a new operator is usually nearer the low end.
Moving up
Every class also needs a high school diploma or GED and the ability to read and write English. Wastewater courses, college and related experience can make up the rest of the total, as described above.
From another state
Illinois has no blanket reciprocity agreement with any state. Illinois EPA reviews each request on its own, comparing the other state's rules and your education and experience with Illinois's requirements.
If your certificate from another state is valid and that state's standards are equal to or stricter than Illinois's, Illinois EPA may certify you at the matching class without an exam. You must live in Illinois or work at an Illinois wastewater treatment or pretreatment works.
Send the application for certification, a copy of your current certificate and the signed verification statement from Illinois EPA's Reciprocity Request. You may take the Illinois exam instead of waiting for the decision. If your experience fits a higher Illinois class than your certificate, you get the lower class unless you pass the Illinois exam for the higher one.
Operator in Training, Collection System and industrial (Class K and R) certificates cannot be transferred by reciprocity. Operators trained in the U.S. Armed Forces may be certified without an exam if they have the hands-on experience for the class.