Water Treatment Operator Certification (US, Class I to IV) Practice Quiz

Under the Environmental Protection Agency's operator certification guidelines, each State's program must require a designated certified operator to be available for each operating shift, and each State develops its own classification system. Each certifying authority chooses which exams it gives, and each certification program decides the content of its own exams. Some programs use the standardized Water Treatment Operator exams of Water Professionals International (WPI, formerly known as the Association of Boards of Certification), delivered by its testing service, ABC Testing, in four classes, I to IV. WPI's 2025 Need-to-Know Criteria for the Class I to IV exams group the content into five areas: Treatment Process, Laboratory Analysis, Equipment Operation and Maintenance, Source Water Characteristics, and Security, Safety, and Administrative Procedures. The exams are multiple choice and closed book, include calculation questions shown in US and metric units, and come with a Formula/Conversion Table.