To calculate the amount of chemical (in pounds) required to achieve a desired dosage (in mg/L) for a given flow rate, adjusted for chemical purity.
The formula is as follows:
Pounds Required = Dosage in mg/L x Flow in MGD x 8.34 / Purity %
8.34 is the weight of one gallon of water in pounds (lbs).
Example Calculation:
A water treatment plant treats 4.5 MGD and desires to dose 1.5 mg/L of chlorine gas. We know that chlorine gas is ~100% pure chlorine.
Pounds Required = 1.5 mg/L x 4.5 MGD x 8.34 / (100/100)
Pounds Required = 56.3
The calculator above converts the % purity to a decimal, so simply enter the purity as the percent shown on the container or SDS.