Water quality standards

Whether water quality is satisfactory will depend on its intended use (e.g. drinking, other domestic usage such as bathing, irrigation, industrial use). Factors such as scarcity will also affect the quality standards applied. Setting these standards, which should be enshrined in law, is the responsibility of the government regulatory authority regarding water in the country or state concerned; WHO has issued international guidelines to facilitate this process although they can be demanding. Some variables are critical to human health and should be checked whatever the level of service; for example, for drinking water, E. coil and total coliform bacteria should not be detectable in any 100 ml sample. However, the high level of public health importance placed on water quality in municipal water and wastewater services may not be appropriate for basic water supply services. Studies have shown that water quantity often plays a more significant role than water quality in improving health and reducing morbidity from water-related disease in low-income communities. The time, energy and difficulty of water-hauling means that, typically, very little water is used in the household for any purpose, and this coupled with inadequate means of excreta disposal has a greater impact on health than lack of safe water. In addition, water often becomes contaminated between the source of supply and its use (see Hygiene education, above). Thus, obtaining high standards of water quality in basic services schemes may be less important than making available a high volume per capita at a close distance to the home. Measuring water quality is a technical procedure; laboratories and suitable equipment will be needed. Further information: WHO, Guidelines for drinking water quality, 1993.