of water and sanitation appropriate technology options in water treatment include both community-scale and household-scale point-of-use (pou) or self-supply designs. such designs may employ solar water disinfection methods, using solar irradiation to inactivate harmful waterborne microorganisms directly, mainly by the uv-a component of the solar spectrum, or indirectly through the presence of an oxide photocatalyst, typically supported tio2 in its anatase or rutile phases. despite progress in sodis technology, military surplus water treatment units like the erdlator are still frequently used in developing countries. newer military style reverse osmosis water purification units (rowpu) are portable, self-contained water treatment plants are becoming more available for public use. for waterborne disease reduction to last, water treatment programs that research and development groups start in developing countries must be sustainable by the citizens of those countries. this can ensure the efficiency of such programs after the departure of the research team, as monitoring is difficult because of the remoteness of many locations. energy consumption: water treatment plants can be significant consumers of energy. in california, more than 4% of the state's electricity consumption goes towards transporting moderate quality water over long distances, treating that water to a high standard. in areas with high quality water sources which flow by gravity to the point of consumption, costs will be much lower. much of the energy requirements are in pumping. processes that avoid the need for pumping tend to have overall low energy demands. those water treatment technologies that have very low energy requirements including trickling filters, slow sand filters, gravity aqueducts. a 2021 study found that a large-scale water chlorination program in urban areas of mexico massively reduced childhood diarrheal disease mortality rates.