A variety of candidate technologies for treatment of household water have been described and many are widely used in different parts of the world. The technologies to improve the microbial quality of household water and reduce waterborne disease include a number of physical and chemical treatment methods. The physical methods, include boiling, heating (fuel and solar), settling, filtering, exposing to the UV radiation in sunlight, and UV disinfection with lamps. The chemical methods include coagulation-flocculation and precipitation, adsorption, ion exchange and chemical disinfection with germicidal agents (primarily chlorine). Some water treatment and storage systems use chemicals and other media and materials that can not be easily obtained locally at reasonable cost and require relatively complex and expensive systems and procedures to treat the water. Such systems may be too inaccessible, complex and expensive to employ for treatment and storage of household water in some places and settings.
The efficacy of some treatment methods to physically remove particles (turbidity) and microbes or to inactivate microbes in household water has been documented, primarily for indicator bacteria. Some treatment methods, such as boiling, solar disinfection, UV disinfection with lamps, chlorination and the combined treatments of chemical coagulation-filtration and chlorination have been evaluated for reductions of bacteria, viruses and in some cases protozoans. However, the ability of some of these methods to remove or inactivate a wide range of known waterborne pathogens has been inadequately investigated and documented.
Studies have shown that improving the microbiological quality of household water by on-site or point-of-use treatment and safe storage in improved vessels reduces diarrheal and other waterborne diseases in communities and households of developing as well as developed countries. The extent to which improving drinking water quality at the household level reduces diarrheal disease probably depends on a variety of technology-related as well as site-specific environmental and demographic factors that require further investigation, characterization and analyses. Reductions in household diarrheal diseases of 6-90% have been observed, depending on the technology and the exposed population and local conditions.
The most promising and accessible of the technologies for household water treatment are filtration with ceramic filters, chlorination with storage in an improved vessel, solar disinfection in clear bottles by the combined action of UV radiation and heat, thermal disinfection (pasteurization) in opaque vessels with sunlight from solar cookers or reflectors and combination systems employing chemical coagulation-flocculation, sedimentation, filtration and chlorination. All of these systems have been shown to dramatically improve the microbiological quality of water.
Further development, refinement, implementation, evaluation and comparison of household water treatment and safe storage technologies is both justified and encouraged.