SOLAIR disinfection of coliform bacteria in hand-drawn drinking water

Abstract

SOLAIR is an alternative disinfection method utilising natural sunlight (specifically UV-A and UV-B radiation) and oxygen (from atmospheric air) to damage, inactivate and / or kill the coliform bacteria found in contaminated water. It is a natural process (virtually self-purification) with no need to add any potentially hazardous chemicals or to use sophisticated and expensive equipment. The SOLAIR process was applied in a typical South African scenario, i.e., a rural informal village where water for domestic use is drawn from an unlined and heavily contaminated well. Results obtained showed significant reduction (99.99%) in both the faecal and total coliform counts within 4 to 6 h, with no subsequent reactivation of growth after 24 h. The disinfected water complied in terms of bacteriological quality, with both the South African Bureau of Standards (SABS), drinking water standards and the South African Water Quality Guidelines (SAWQG) for domestic use as prescribed by the Department of Water Affairs and Forestry (DWAF). The rate of bacterial reduction depended on various parameters including the type and colour of plastic containers used, the initial concentration of micro-organisms in the drawn water, the irradiation levels of UV-A and UV-B rays, the oxygen concentration and distribution in the water containers, and the presence of visible turbidity. In South Africa where more than 8 m. people are still using water obtained directly from alternative sources such as rivers, streams, boreholes, wells, community taps and dams, SOLAIR could prove to be an efficient and an economically feasible method to be used for disinfection of hand-drawn water to an acceptable potable standard. WaterSA Vol.27(1) 2001: 49-52