TECHNIQUES FOR POTABLE WATER TREATMENT USING APPROPRIATE LOW COST NATURAL MATERIALS IN THE TROPICS

Abstract

The effectiveness of mechanical filtration and solar irradiation in water treatment was evaluated. Selected metals and non-metals ions before and after treatment were determined colorimetrically while turbidity was measured using a turbidimeter. pH, electrical conductivity, dissolved oxygen (DO) and temperature were measured using a portable universal multiline P4 WTW meter while total alkalinity was determined titrimetrically. The load of coliform bacteria contamination before and after treatment was determined by Millipore filtration method. Screening for the presence of pathogenic bacteria was carried out using standard methods. The levels of the properties before and after treatment were each compared with the recommended drinking water standards according to Kenya Bureau of Standards (KEBS) and World Health Organization (WHO). The water was treated by being subjected to mechanical filtration and solar irradiation and changes in their physico-chemical properties and bacteriological load determined. The results obtained after treatment revealed that solar irradiation killed most of the pathogenic bacteria after exposure for eight hours but had no impact on the physico-chemical properties except nitrates (from 24.5 to 8.0 mg.L-1). Mechanical filtration reduced total coliforms and E. coli by 30 %. It also reduced the loads of Zn, Cu, Mn, Pb, Fe, nitrate nitrogen and turbidity of the water treated to an almost potable state. Water treatment using a combination of mechanical filtration system and solar disinfection was found to be very effective in reducing the bacterial load.