Level 1 · Entry sample questions
5 free sample questions on math and calculations for the Level 1 · Entry wastewater treatment operator exam. Try each one, then open the answer to check your work.
A treatment plant receives 0.75 million gallons per day. What is the flow in gallons per day?
Answer: D. 750,000 gallons per day
One million gallons equals 1,000,000 gallons, so 0.75 MGD equals 750,000 gallons per day. Calculation: 0.75 × 1,000,000 = 750,000 gallons per day.
Influent BOD is 200 mg/L and effluent BOD is 40 mg/L. What is the BOD removal?
Answer: C. 80%
The plant removes 160 mg/L from an influent concentration of 200 mg/L. Dividing the amount removed by the influent concentration gives 0.80, or 80%. Calculation: ((200 − 40) ÷ 200) × 100% = 80%.
An aeration basin holds 500,000 gallons and receives a flow of 1.0 million gallons per day. What is the detention time in hours?
Answer: B. 12 hours
Dividing basin volume by daily flow gives 0.5 day. Converting one-half day to hours gives 12 hours. Calculation: 500,000 gal ÷ 1,000,000 gal/day = 0.5 day; 0.5 day × 24 hr/day = 12 hours.
A plant treats 1.0 MGD with an influent BOD concentration of 150 mg/L. What is the BOD loading in pounds per day?
Answer: A. 1,251 lb/day
The pounds formula combines flow in MGD, concentration in mg/L, and the 8.34 conversion factor to calculate the daily BOD mass loading. Calculation: 1.0 × 150 × 8.34 = 1,251 lb/day.
A plant flow is 1.44 MGD. What is the flow in gallons per minute?
Answer: C. 1,000 gpm
Convert 1.44 million gallons to 1,440,000 gallons, then divide by 1,440 minutes per day to obtain 1,000 gallons per minute. Calculation: (1.44 × 1,000,000) ÷ 1,440 = 1,000 gpm.
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