Work out chlorine residual instantly with clear inputs, formula shown and shareable results.
Chlorine decays approximately first order: C = C0 x e^(-kt). Bulk and wall decay coefficients depend on organic content, temperature and pipe condition, ranging from 0.02 per hour in clean cold water to over 0.5 per hour in warm water with tuberculated mains. Long travel times need booster chlorination rather than a higher initial dose.
First-order decay
C = C0 x e^(-k t)
Source dose
Required source residual = minimum residual x e^(k t)
Maintaining a disinfectant residual is a regulatory requirement in most distribution systems. Verify residuals by field measurement at representative sampling points.
It creates high residuals and disinfection by-products near the works, causing taste and odour complaints and regulatory exceedances, while still failing at the extremities. Booster dosing is the correct answer.
By bottle tests for bulk decay and by comparing modelled with measured residuals in the field to calibrate the wall decay term. It must be re-measured seasonally because temperature dominates.