Water quality : wastewater treatment

Urban water services can include any or all of the following: (a) provision of water for domestic and industrial uses; (b) sanitation to remove human wastes from possible contact with humans; and (c) treatment of wastes to remove contaminants. Whereas the removal of wastes-sanitation-confers well-established and obvious health benefits on urban residents, the treatment of the wastes provides benefits for downstream communities. These benefits emerge primarily as environmental improvements, which support the environmental services that these communities rely on, although there can be health benefits too, particularly if disinfection is included in the treatment to remove pathogens. Sanitation sources can be provided wither using water as a carrier (e.g., sewerage systems) or not (e.g., pit latrines). Whether waterborne sanitation technologies are used or not, it is important to make sure that the wastes are treated before thy get to waterbodies in order to protect downstream communities. Thus, poorly sited or maintained latrines can contaminate waterbodies because the usual soil processes are not able to remove nutrients and disable pathogens before the wastes emerge into the environment.