Daily chlorine requirement in all three common forms + contact tank sizing + CT value per CPHEEO Chapter 9.
📘 Read the full CPHEEO Chapter →Disinfection is non-negotiable in Indian water supply — the single most important step for protecting consumers from waterborne disease. Chlorination is the standard method, but the form of chlorine used depends on scale: large WTPs use chlorine gas (most economical); medium plants use sodium hypochlorite solution (safer); small/rural schemes use bleaching powder (calcium hypochlorite — cheap and easy to handle).
This calculator converts a single chlorine dose (mg/L) into the required daily quantity of whichever form you're using. It also computes the contact tank volume needed to achieve the minimum 30-minute contact time per CPHEEO and gives the CT (concentration × time) value for comparison against WHO thresholds (≥ 15 for E. coli, ≥ 30 for viruses, ≥ 100+ for Cryptosporidium).
Based on the CPHEEO Manual on Water Supply and Treatment, published by the Central Public Health and Environmental Engineering Organisation, Ministry of Housing and Urban Affairs, Government of India.
Compute daily chlorine requirement for any plant capacity and convert to the three common chlorine forms used in Indian water supply.
Daily chlorine mass drives procurement. For chlorine gas, you'll see consumption in kg/day mapped to the number of 100 kg cylinders per week. For bleaching powder, daily kg drives the storage shelf life (bleaching powder degrades 5-10% per month in tropical heat). For sodium hypochlorite, daily L drives the tanker delivery frequency.
Contact tank volume is often larger than expected — a 10 MLD plant needs ~200 m³ of contact tank (10,000 m³/day × 30/60/60 min × 60 min). This is why WTPs have dedicated contact tanks, not just clear water reservoirs.