Filtration, Backwash & Residuals — Water Treatment Operator Practice Test
Free drinking-water treatment operator certification practice in English, Chinese, and Spanish — coagulation and sedimentation, filtration and residuals, disinfection chemistry, plant equipment, instrumentation and control, the laboratory bench, source water, and safety and compliance.
20 free practice questions
Practice questions written against the standardized Water Treatment Operator Need-to-Know Criteria published by Water Professionals International (formerly the Association of Boards of Certification) and standard references from the CSUS Office of Water Programs and AWWA. This site is not affiliated with or endorsed by WPI/ABC, AWWA, or the US EPA. Operator certification is issued by your state's certifying authority, which sets plant classification tiers, operator grades, eligibility, and the passing standard — confirm those with your state before testing. Contaminant limits and monitoring requirements are set federally and are revised over time, so no answer here should be relied on as a current regulatory value; consult the regulations in force for your system. This bank covers the drinking-water treatment exam only — wastewater treatment, wastewater collection, and water distribution are separate certifications. About the Need-to-Know Criteria →