Desirable in Disinfection
Chlorine (Cl2) is a gas, heavier than air, toxic, non-flammable and an economically available oxidizing agent that provides properties desirable in disinfection usage. Chlorine is available in one of three forms: sodium hypochlorite, calcium hypochlorite and liquid chlorine.
- Sodium hypochlorite, commonly called “liquid bleach”, is commercially available in strengths approximately 15% by weight. It can be added to the receiving stream by gravity, by the use of a chemical metering pump, or by physically dumping it.
- Calcium hypochlorite, generally referred to as “powder chlorine”. It contains 70% available chlorine. It can be added to the receiving stream by use of pellets or by mixing a solution of water and calcium hypochlorite, decanting the solution into a tank and using a small chemical feed pump.
- Liquid chlorine, known also as “chlorine gas”, is chlorine in its elemental form. It is available as a compressed gas of 100% strength. The most common ways of adding elemental chlorine to a receiving stream are to feed gas with a vacuum-operated solution feed system, or to feed the gas under pressure.
When comparing elemental chlorine as an oxidizing agent to powder (calcium hypochlorite) or solution (sodium hypochlorite), the oxidizing effect is the same. That is, all three produce hypochlorous acid, the oxidizing agent present for disinfection in water and waste water application. When chlorine gas is dissolved in water, it also reacts with the water to form hypochlorous acid and hydrochloric acid: