Step 3: Disinfection of the well
WHO endorses the disinfection of drinking water in emergency situations. There are various ways of doing this but the most common is chlorination as it leaves a residual disinfectant in the water after chlorination.
Chlorine has the advantage of being widely available, simple to measure and use and dissolves easily in water. Its disadvantages are that it is a hazardous substance (handled with care) and is not effective against all pathogens (e.g. cysts and viruses, which require higher chlorine concentrations).
The chlorine compound most commonly used is calcium hypochlorite as high test hypochlorite (HTH) in powder or granule form. Also used is sodium hypochlorite in liquid bleach or bleaching powder form. Each chlorine compound has a different amount of usable chlorine depending on the quantity of time the product has been stored or exposed to the atmosphere and the way it is made.