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Solutions to Sedimentation Tank Math

 

1. The circumference of a sedimentation tank is ________ feet.

3.14 x 75 ft = 235.5 ft

 

2. The surface area of a sedimentation tank is ________ square feet.

0.785 x 75 ft x 75 ft = 4,415.625 sf

 

3. The volume of a sedimentation tank is ________ cubic feet.

Cylinder:           0.785 x 75 ft x 75 ft x 8 ft = 35,325 cf

Cone:   (0.785 x 75 ft x 75 ft x 4 ft) ÷ 3 = 5,888 cf

Tank:    35,325 cf + 5,888 cf = 41,213 cf

 

4. A sedimentation tank holds  ______ gallons.

41,213 cf x 7.48 gal/cf = 308,273 gal

 

5. The detention time of a sedimentation tank is _______ minutes.

(308,273 gal ÷ 7,500,000 gpd) x 1440 min/day = 59 min

 

6. The detention time of a sedimentation tank is _______ hours.

(308,273 gal ÷ 7,500,000 gpd) x 24 hrs/day = 0.99 hrs

 

7. The surface settling rate of a sedimentation tank is _______ gpd/square foot

7,500,000 gpd/4415.625 sf = 1,699 gpd/sf

 

8. The weir overflow rate of a sedimentation tank is ________ gpd/ft

7,500,000 gpd/235.5 ft = 31,847 gpd/ft

 

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