Work out chlorine dose for water instantly with clear inputs, formula shown and shareable results.
Chlorine mass required is flow times dose: 1 mg/L on 1000 cubic metres is 1 kilogram. Dividing by the product's available chlorine gives the weight of bleaching powder or hypochlorite to dose. The residual is the dose less the chlorine demand consumed by organics, ammonia, iron and manganese.
Chlorine dose
Chlorine (kg/day) = flow (m3/day) x dose (mg/L) / 1000
Residual
Free residual = dose - chlorine demand
Chlorination is a critical public health barrier. Doses must be verified by residual measurement, and chlorine gas and concentrated hypochlorite are hazardous chemicals requiring specific safety controls.
Typically 0.2-0.5 mg/L free chlorine at the far end of the distribution network, with 0.5-1.0 mg/L leaving the works to allow for decay. Local standards vary and take precedence.
Where ammonia is present, chlorine first forms chloramines and free residual only appears once enough chlorine has been added to oxidise the chloramines — the breakpoint, at roughly 7.6 times the ammonia nitrogen.