Fact sheet (CDC, USAID) : Household water treatment and safe storage (HWTS) interventions are proven to improve water quality and reduce diarrheal disease incidence in developing countries. Four of these HWTS options – chlorination, solar disinfection, ceramic filtration, and flocculation/disinfection – are proven to improve microbiological quality and reduce diarrheal disease in developing countries. Other options – including BioSand Filters – are widely implemented but are not yet specifically proven to reduce diarrheal disease incidence in peer-reviewed research. Organizations wanting to develop HWTS programs are often faced with the difficult decision of selecting which option or options are appropriate for their particular circumstances, and how to choose between proven and unproven options. The most appropriate HWTS option for a location depends on existing water and sanitation conditions, water quality, cultural acceptability, implementation feasibility, availability of HWTS technologies, and other local conditions. This series of fact sheets is designed to assist organizations in comparing, and ultimately selecting, the appropriate HWTS option or options. For more information on household water treatment, please visit www.who.int/household_water. For more information on BioSand Filtration, please visit www.cawst.org or www.bushproof.org.