If the desired dosage is 6.4 mg/L and the demand is 3.1 mg/L, what is the resulting residual?

To determine the resulting residual when given the desired dosage and demand, you subtract the demand from the desired dosage. In this case, with a desired dosage of 6.4 mg/L and a demand of 3.1 mg/L, you perform the following calculation:

Residual = Desired Dosage - Demand

Residual = 6.4 mg/L - 3.1 mg/L

Residual = 3.3 mg/L

This calculation shows that after satisfying the demand of 3.1 mg/L, you still have 3.3 mg/L left as a residual. This residual indicates the amount of the chemical that remains in the water after the demand has been met, reflecting how efficiently the treatment process has worked. A clear understanding of how to calculate residuals is crucial in managing surface water treatment processes, ensuring that adequate chemical dosages are applied to meet both demand and desired levels of treatment.