Industrial Wastewater Operator Math: Loadings, Dosing and Sizing
Calculation questions are a consistent share of any operator examination, and in industrial
pretreatment they cluster around a small number of relationships. Learn these and the rest is
arithmetic.
The core relationships
Pounds per day = Concentration (mg/L) x Flow (MGD) x 8.34
Percent removal = (In - Out) / In x 100
Volume (cu ft) = Length x Width x Depth
Gallons = Cubic feet x 7.48
Detention time = Volume / Flow rate
Pounds of chemical = Dose (mg/L) x Volume (MG) x 8.34
The factor 8.34 is the weight of a gallon of water in pounds. It is what converts a
concentration and a volume into a mass.
Why mass loading is the pretreatment calculation
A control authority may express a limit as pounds per day rather than as a concentration,
precisely because the b