Hello.

Are you talking about using chlorination as treatment (for example, primary oxidation), distribution or both? If for a primary treatment you should do some pilot scale studies so that you come up with a reasonably accurate value. The amount will depend on the characteristics of the water initially.

For distribution you should be ok with a concentration of NaOCl or ClO2 equivalent to 0.3 - 0.5 mg of Cl2 /L. I recommend using chlorine dioxide if you can. Tends to be more stable and provide more efficient disinfection.

Cheers!

Quality of the water will dictate the chlorine dose required for its treatment. Typically one has to conduct a dose-response study to determine how much disinfectant is needed. The actual dose would be a little in excess of that required for break-point chlorination to deal with issues in the distribution system and ensure delivery of safe water to the consumers.

The required amount depend on the pH, Temperature and dissolved substances of water.

In normal cases, to keep the water safe, maintain chlorine residual of 0.3-0.5 mg/L. In this regards you need 30000 mg (30 grams Cl gas) to 50000 mg (50 grams Cl gas).

If the water contain some bad smell, the dose is increased ten times 3 to 5 mg/L. For 100000 L water the calculated amount will be 300 grams to 500 grams Cl gas. It is called super chlorination. In such cases, excess of Cl residue is removed through adsorption by activated charcoal.

Besides Cl gas, other compounds of Cl can also be used, such as Sodium hypochlorite solution (NaOCl) or solid calcium hypochlorite (Ca(OCl)2.

4mg per liter

Therefore, For 100000= 0.004* 1,00,000 = 400 gm