What is the hydraulic detention time for a rectangular tank measuring 26 ft by 22 ft by 19 ft with an influent flow of 1.3 MGD?

To calculate the hydraulic detention time for a rectangular tank, you first need to determine the volume of the tank and then calculate how long it takes for the influent flow to fill that volume.

The volume of the tank can be found using the formula for the volume of a rectangular prism:

Volume = Length × Width × Height

In this case, the tank's dimensions are 26 feet (length), 22 feet (width), and 19 feet (height). Thus, the volume is:

Volume = 26 ft × 22 ft × 19 ft = 10,924 cubic feet.

Next, to convert this volume into gallons (since the flow rate is provided in million gallons per day, or MGD), note that 1 cubic foot is equivalent to approximately 7.48 gallons. Therefore:

Volume in gallons = 10,924 cubic feet × 7.48 gallons/cubic foot ≈ 81,773 gallons.

Now that we have the volume of the tank in gallons, we can calculate the hydraulic detention time using the formula:

Hydraulic Detention Time (hours) = Volume (gallons) / Flow Rate (gallons/hour).

The influent flow is given as 1.3 MGD