How do scientists use Sodium Hypochlorite to treat drinking water?
Again, we need to understand that using sodium hypochlorite is a portion of the water treatment process. In the simplest terms, here’s how it works: Fresh source water and salt are combined to make brine (salt water). Using an electric conductor, electricity is passed through the brine making hypochlorite. The hypochlorite is then poured into the untreated body of source water and shaken. The addition of sodium hypochlorite to the water kills existing bacteria, purifies the water and ensures it is safe to drink.

Sodium Hypochlorite Formation
Brine (salt water) + Energy (Electricity) Sodium Hypochlorite and Hydrogen Gas

Using Sodium Hypochlorite for Water Treatment

Sodium Hypochlorite + Water Caustic Soda + Hypochlorous Acid

Hypochlorous Acid + (Bacteria, Protozoa, Dirt, Soil) Hydrochloric Acid + Caustic Soda + (Oxidized Bacteria, Protozoa, Dirt, Soil)

Hydrochloric Acid + Caustic Soda Treated Water + Salt

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Sodium hypochlorite, otherwise known as “bleach” is generated by the electrolysis of weak brine. Sodium hypochlorite cells generally do not require saturated brine, but can utilize weak brine or even seawater. Bleach is produced “on-site” for disinfection of drinking water and wastewater. The cells employed for this purpose are the same as those used for chlorate manufacture, that is, they consist of an anode and a cathode without a separator or diaphragm. The anodic and the cathodic reactions are the same as in chlor-alkali and chlorate cells, the difference being the pH of the electrolyte, which is maintained in the range of 10 to 12. The electrolytically generated chlorine reacts with sodium hydroxide to form sodium hypochlorite. However, the hypochlorite ion, formed in the bulk, is easily reduced at the cathode to reform chloride. Therefore, only dilute solutions of bleach can be produced in the cell. Hypochlorite can also react further to form chlorate, but this can be minimized by keeping the solution basic and the temperature low (close to room temperature).

NaCl + H2O ==> NaOCl + H2 (overall hypochlorite reaction)

The Cl- is released when we add NaOCl back into H2O.