TradeExamPro › Water & Wastewater
100 free practice questions for this exam, each with the reason for the answer and where to look it up.
10 questions, graded as you go, with the reason for every answer. No sign-up.
| Exam | Wastewater collection operator Grades 1 to 4 |
|---|---|
| Who runs it | State agencies |
| Where | United States (varies by state) |
Question count, time limit and pass mark differ by where you take it. Check the official candidate bulletin from the organisation that runs your exam.
A circular clarifier is 40 ft in diameter with a water depth of 16 ft. What is its volume in gallons? Use area = 0.785 × D² and 7.48 gal/ft³.
Answer in gal.
150320 gal
Surface area = 0.785 × 40² = 0.785 × 1,600 = 1,256 ft². Volume = 1,256 × 16 = 20,096 ft³. Gallons = 20,096 × 7.48 = 150,318 gal, about 150,320 gal.
Reference: Cylinder volume: V = 0.785 × D² × depth; 7.48 gal/ft³
What oxygen range is acceptable for entering a confined space without supplied air?
A. 19.5% to 23.5%
Normal air is 20.9% oxygen. OSHA treats an atmosphere below 19.5% as oxygen-deficient and one above 23.5% as oxygen-enriched, which is a fire hazard. Entry outside this range requires ventilation or supplied-air breathing apparatus.
Reference: OSHA 29 CFR 1910.146: permit-required confined spaces (hazardous atmosphere)
Why is grit removed early in the treatment process?
C. To prevent pump wear and deposits in tanks
Grit is sand, gravel and other heavy inorganic material. It abrades pumps and piping and settles in channels and digesters, taking up volume. Because it is inorganic, removing it does little for BOD or odor.
Reference: Preliminary treatment: grit removal
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Water treatment operator Grades 1 to 4 · Water distribution operator Grades 1 to 4 · Wastewater treatment operator Grades 1 to 4 · Aquatic facility operator