Detention time in a tank is calculated by dividing which two factors?

Detention time, also known as residence time, is fundamental in water treatment processes as it indicates how long water remains in a tank. To calculate detention time, the appropriate formula is the tank's volume divided by the flow rate entering the tank.

Choosing tank capacity rather than volume could cause confusion, but in this context, tank capacity is commonly understood to refer to the total volume of water that the tank can hold. Flow rate, measured in volume per time (e.g., gallons per minute), tells us how quickly water enters or exits the tank.

So, dividing the tank’s capacity (or volume) by the flow rate gives a measure of time, which indicates how long the water stays in the tank before it is displaced or treated. If the flow rate is high relative to the tank’s capacity, the detention time will be lower, meaning the water spends less time in the tank. Conversely, a lower flow rate in relation to the capacity means water remains in the tank longer. This calculation is crucial in designing and managing water treatment systems effectively.

Understanding this relationship helps operators ensure adequate treatment and contact time, which is essential for processes such as sedimentation and disinfection.