Calculate the detention time in hours for a circular tank with a flow of 1.42 MGD. The tank is 45 feet in diameter and 10 feet deep.

• A. 2 hours
• B. 3 hours
• C. 1 hour
• D. 4 hours

Answer: (A)

To calculate the detention time for the circular tank, it is essential to determine both the volume of the tank and the flow rate in a consistent unit, then use the formula for detention time.

First, calculate the volume of the circular tank. The formula for the volume ( V ) of a cylindrical tank is given by:

[

V = \pi r^2 h

]

where ( r ) is the radius of the tank and ( h ) is the height (or depth) of the tank. In this case, the diameter of the tank is 45 feet, which means the radius ( r ) is half of that:

[

r = \frac{45 \text{ ft}}{2} = 22.5 \text{ ft}

]

The depth ( h ) is given as 10 feet. Now substituting these values into the volume formula:

[

V = \pi (22.5 \text{ ft})^2 (10 \text{ ft}) = \pi (506.25 \text{ ft}^2) (10 \text{ ft}) = 5062.5 \pi \text{ ft}^3

]

Next, calculating