Median Pay by Area
- Madison
- $71,850 a year
- Green Bay
- $67,190 a year
- Milwaukee-Waukesha
- $66,980 a year
- Appleton
- $64,820 a year
- Eau Claire
- $63,550 a year
Wisconsin wastewater operators
The steps from no certificate to a Wisconsin wastewater operator certificate: which exams to take, how to apply by mail, how Operator-in-Training, Basic and Advanced work, how to keep your certificate active and what operators earn. Every requirement links to the Wisconsin Department of Natural Resources (DNR) Operator Certification Program or its rule, Wis. Admin. Code chapter NR 114.
DNR makes the final eligibility determination. Check with DNR before you apply.
Why it matters
Wisconsin law says no one may operate a wastewater treatment plant without a valid certificate from DNR. The owner of a wastewater treatment plant must be, or employ, a certified operator responsible for plant operations.
Every treatment plant with a WPDES permit must have a designated operator-in-charge certified at the plant's level and in all of the plant's subclasses, except laboratory. A plant with a registered or certified laboratory needs at least one operator who works in the lab certified at the Basic level in the Laboratory subclass.
An owner whose treatment plant includes the sanitary sewage collection system to it must also designate a collection system operator-in-charge certified in the Sanitary Sewage Collection System subclass. For satellite collection systems, certification is voluntary, though DNR highly recommends it.
A Wisconsin certificate has a level and one or more subclasses. The levels are Operator-in-Training (OIT), Basic and Advanced. The subclasses match treatment processes: A1 Suspended Growth, A2 Attached Growth, A3 Recirculating Media Filters, A4 Ponds, Lagoons and Natural Systems, A5 Anaerobic Treatment of Liquid Waste, B Solids Separation, C Biological Solids/Sludge, D Disinfection, L Laboratory, N Total Nitrogen, P Total Phosphorus, SS Sanitary Sewage Collection System and U Unique Treatment Systems.
Each plant is rated basic or advanced. A plant is advanced if it meets any one of these: a mechanical plant with an annual average design flow over 1.0 MGD, a BOD limit of 10 mg/L or less, biological nutrient removal with phosphorus or nitrogen limits, tertiary phosphorus removal for ultralow limits, a municipal plant receiving wastewater from a major contributing industry, or a municipal plant producing Class A biosolids.
Collection systems only require Basic level certification, even when the treatment plant is advanced.
Step 1
To become certified, pass the Wastewater - General exam and at least one subclass exam. Choose subclasses that match the processes at the plant where you work or want to work. The General exam is not required for the Sanitary Sewage Collection System (SS) or Unique Treatment Systems (U) subclasses.
No prior education or training is required before taking the exams, though DNR recommends some classroom or online training.
DNR publishes a free study guide for the General exam, each subclass and the Advanced exam. The Basic General study guide says every test question and answer comes directly from one of its key knowledges, and it includes a chapter on calculations.
Step 2
Fill out the Wastewater Operator Certification Exam Application (Form 3400-837), mark your exam session and the exams you want, and mail it with your fee to the DNR Operator Certification Program. Applications are accepted by mail only.
Each basic exam costs $25 and the Advanced exam $50. Pay by check, money order or cash, with checks made out to Wisconsin DNR. Exam fees are not refundable. A veteran may ask for a fee waiver for a first-time operator certificate.
Your application must be postmarked at least four weeks before the exam date. Your name must exactly match your photo ID, and you must provide your Social Security number, which state law requires for tax and child support checks.
DNR reviews applications within 10 business days and mails you a confirmation letter with the exam location. From mailing to confirmation usually takes 2 to 3 weeks.
Step 3
Passing the General exam and a subclass exam makes you an Operator-in-Training in that subclass. To reach Basic in a subclass, you also need one year of experience in that subclass.
One year means full-time work at a treatment plant, or 1,000 hours over at least 12 months for part-time operators. Your first 12 months must be in the specific subclass; later experience can be any general wastewater operating experience.
Experience must be daily hands-on operation and maintenance, or daily on-site technical supervision of the operators doing that work. Lab analysis (except for the Laboratory subclass) and management work not tied to day-to-day operation do not count, and education cannot replace hands-on experience.
Document your experience on the Wastewater Operator Certification Experience Form (3400-066A), one form per facility, signed by your supervisor. Mail or email it to your DNR regional coordinator.
Step 4
Advanced certification takes 10 points, and you need Basic certification first. At least 4 points must come from hands-on experience, so you need at least four years of it. Experience earns 4, 5 or 6 points for 4, 5 or 6 years; 6 is the most.
Other points: 6 for a wastewater-related associate's degree, a bachelor's or graduate degree with at least 240 hours of wastewater-related courses, or a state-approved apprenticeship; 4 for passing the 100-question Advanced exam; and 0.5 to 2 for 20 to 80 hours of DNR-approved advanced coursework.
Send the Advanced Wastewater Treatment Plant Operator Certification Application (Form 3400-211) with a $100 application fee. Attach diplomas and transcripts if you claim a degree, and certificates for advanced courses.
Step 5
Certificates expire three years from the date they are issued. Adding subclasses or moving up a level does not change the expiration date.
Each three-year period, Operator-in-Training and Basic operators need 18 hours of continuing education, and Advanced operators need 24. Each hour of course learning is one credit, and credits must be earned within your certificate period; extra credits do not carry over.
Up to 6 hours of health and safety training count per period. Supervisor or management training counts for up to 3 hours for Operator-in-Training and Basic operators, and up to 6 for Advanced operators. Training must be relevant to wastewater treatment plant operation.
DNR's training page lists pre-approved courses and online providers. For relevant training that was not pre-approved, send the Operator Training Report Form (4400-190) with proof of attendance. One CEU from a training provider equals 10 continuing education credits.
DNR mails a courtesy reminder six weeks before your certificate expires, but tracking the date is your job. Renew online through DNR's renewal portal, or by mail with your continuing education documentation and the $45 renewal fee, postmarked by the expiration date. A late renewal adds a $25 penalty.
You have one year after expiration to reinstate, but you are not a certified operator during the lapse. After a year, you must retake the exams as a new operator.
Exam day
In 2026, DNR staff give the exams in person, on paper, at locations around the state, about three times a month every other month. Each exam day has two three-hour sessions, at 9 a.m. and 1 p.m., and you can take as many exams as you like in a session.
The Wastewater - General exam has 50 questions. Subclass exams have 25 questions (Attached Growth, Recirculating Media Filters, Anaerobic Treatment of Liquid Waste and Total Nitrogen) or 50 (the rest), and the Advanced exam has 100. All are multiple choice except Unique Treatment Systems (U), a short-answer exam.
A score of 75 percent or higher passes each exam.
Wastewater exams are closed book. Bring a photo ID, a #2 pencil and a basic calculator; you may not use your phone as a calculator. Arrive at least 15 minutes early for check-in.
Results are mailed within 2 to 4 weeks, with a list of missed objectives to show which study guide areas to review. To retake an exam, send a new application and fee for a later session.
Wisconsin DNR writes and gives its own exams, and every question comes from the key knowledges in DNR's study guides. The DNR pages we read do not mention a formula sheet handed out at the exam, and the exams are closed book. Operator Master's free practice questions, timed practice exam and math help are built on the WPI exam format and the WPI formula table, so use them for general wastewater knowledge and math, and use DNR's study guide for each exam you take as your main guide. 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 Wisconsin was $63,550 a year ($30.56 an hour) in 2025, compared with $60,020 nationally. One in ten earned $50,340 or less, and one in ten earned $78,790 or more.
These federal figures cover drinking water and wastewater operators together, at every level. Pay for a new operator is usually nearer the low end.
Moving up
Levels are earned subclass by subclass. One year of experience means full-time work at a treatment plant, or 1,000 hours over at least 12 months part-time, and the first year must be in that subclass. The General exam is not required for the SS and U subclasses. If you already hold Advanced in one subclass, a new subclass moves up to Advanced once you pass its exam and document a year of experience in it.
From another state
NR 114 lets DNR issue a certificate without exams, at a comparable level and subclass, to someone who holds a current wastewater treatment plant operator certificate from another state, territory or country, if DNR judges that the person meets Wisconsin's equivalent exam, education and experience requirements. DNR's forms page says you must have taken one or more exams for that certificate.
Send the Wastewater Operator Reciprocity Application (Form 3400-219), the Social Security Number request form, a cover letter or resume, a copy of your current certificate, an experience form for each facility you worked at and the $100 fee. Adding an Advanced application brings the total to $200.
Allow 1 to 3 months for DNR to verify and review your application.