A typical recommendation for disinfecting water by boiling is to bring the water to a rolling boil for 10-12 minutes. Chlorination is the most widely used method for disinfecting drinking water. Iodine is another excellent chemical disinfectant that is sometimes used. Both chlorine and iodine must be added in sufficient quantities to destroy all pathogens but not so much that taste is adversely affected. Deciding on the right amount can be difficult because substances in the water will react with the disinfectant, and the strength of the disinfectant may decline with time depending on how it is stored.
Solar disinfection uses solar radiation to inactivate and destroy pathogens present in water.
Filtration includes mechanical straining, absorption and adsorption, and, particularly in slow sand filters, biochemical processes. Depending on the size, type and depth of filter media, and the flow rate and physical characteristics of the raw water, filters can remove suspended solids, pathogens, and certain chemicals, tastes and odors. Straining and settlement are treatment methods that usefully precede filtration to reduce the amount of suspended solids that enter the filtration stage. This increases the period for which a filter can operate before it needs cleaning or replacing. Coagulation and flocculation are also useful treatments to precede settlement and improve still further the removal of solids before filtration.