Preliminary and Primary Treatment Questions
Headworks and primary clarifiers fall under Equipment Evaluation, Maintenance and Operation, 39 of the 100 questions on WPI’s Wastewater Treatment Class I exam, and under the Class D criteria in Texas.
100 questions in the official content counts, with a score for every area and an explanation for every option.
Or try the free primary treatment drill- 32 original primary treatment questions, every option explained
- Tested on 7 of our 25 practice exams
Why is grease in the influent a problem?
What our primary treatment questions cover
- What wastewater is: BOD, solids, flow patterns, fresh and septic
- Bar screens, screenings, comminutors and grit chambers
- Primary clarifiers: removal rates, sludge pumping, scum and weirs
- Imhoff tanks, pre-aeration, grease and industrial pretreatment
- Flow equalization and overflow rate
This list is our own summary, written for practice. The exam owners publish their outlines: California’s Expected Range of Knowledge, TCEQ’s Need-to-Know Criteria and WPI’s Need-to-Know Criteria.
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100 questions in the official content counts, with a score for every area and an explanation for every option.
Or try the free primary treatment drillIdeas the questions test most
- Grit chambers run near 1 ft/s.
- Primaries remove about 25–35% of BOD and 50–65% of suspended solids.
- Septic sludge rises and smells of H2S.
- Level weirs prevent short circuiting.
Start the free primary treatment drill · Wastewater Treatment Class I practice test · California Wastewater Grade I practice test · California Wastewater Grade II practice test · TCEQ Class D Wastewater practice test · TCEQ Class C Wastewater practice test · TCEQ Collection Class I practice test
Common questions
What does a primary clarifier remove?
Settleable and floatable solids: roughly half or more of the suspended solids and about a quarter to a third of the BOD. Dissolved BOD is left for secondary treatment.
Why remove grit?
Sand and gravel wear pumps and fill tanks and digesters; they do not break down.
100 questions in the official content counts, with a score for every area and an explanation for every option.
Or try the free primary treatment drillMore operator topics
Outlines used for these questions: Expected Range of Knowledge, Drinking Water Treatment Exam (rev. 4/2020, PDF) · Expected Range of Knowledge, Drinking Water Distribution Exam (rev. 4/2020, PDF) · TCEQ: Need-to-Know Criteria for public water system operators · TCEQ: What applicants for wastewater licenses need to know · WPI: 2025 Need-to-Know Criteria.
Game Assessment Prep is an independent practice site, not affiliated with or endorsed by Water Professionals International (WPI, formerly ABC), the California State Water Resources Control Board or the Texas Commission on Environmental Quality. Every question is original; none is taken from a certification exam, an official study guide or another prep provider.