Wastewater Operator Wastewater Math and Calculations Questions and Answers

Question 1

A treatment plant's influent flow of 4.2 MGD has an average Biochemical Oxygen Demand (BOD) concentration of 210 mg/L. How many pounds of BOD enter the plant each day?

Accepted Answer

7,356 lbs/day

Answer

882 lbs/day

Answer

73,560 lbs/day

Answer

8,820 lbs/day

Question 2

An activated sludge system has the following characteristics: Influent flow to the aeration basin is 1.5 MGD, primary effluent BOD is 150 mg/L, the aeration tank volume is 0.5 MG, and the Mixed Liquor Suspended Solids (MLSS) is 2,800 mg/L. What is the Food to Microorganism (F/M) ratio?

Accepted Answer

0.16

Answer

0.05

Answer

1.25

Answer

6.22

Question 3

A circular clarifier is 60 feet in diameter and 12 feet deep. If the influent flow rate is 2.5 MGD, what is the detention time in hours?

Accepted Answer

2.4 hours

Answer

0.1 hours

Answer

4.1 hours

Answer

1.8 hours

Question 4

An operator performs a 30-minute settleability test on a mixed liquor sample, and the settled solids occupy a volume of 320 mL/L. The MLSS concentration is determined to be 2,500 mg/L. What is the Sludge Volume Index (SVI) in mL/g?

Accepted Answer

128 mL/g

Answer

7.8 mL/g

Answer

0.13 mL/g

Answer

80 mL/g

Question 5

A pump is required to move 500 gallons per minute (gpm) against a total head of 45 feet. What is the water horsepower (WHP) required?

Accepted Answer

5.7 WHP

Answer

2.8 WHP

Answer

88.0 WHP

Answer

11.4 WHP

Question 6

What is the weir overflow rate (WOR) in gpd/ft for a circular clarifier that has a diameter of 80 feet and receives a flow of 3.0 MGD?

Accepted Answer

11,943 gpd/ft

Answer

37,500 gpd/ft

Answer

15,000 gpd/ft

Answer

5,971 gpd/ft

A treatment plant's influent flow of 4.2 MGD has an average Biochemical Oxygen Demand (BOD) concentration of 210 mg/L.How many pounds of BOD enter the plant each day?

A treatment plant's influent flow of 4.2 MGD has an average Biochemical Oxygen Demand (BOD) concentration of 210 mg/L.
How many pounds of BOD enter the plant each day?