Abstract

Water supply systems provide consumers with drinking water that is adequately free of microbial pathogens to prevent waterborne diseases. The key to produce water of such desired quality is to implement multiple barriers, which control microbiological pathogens and chemical contaminants that may enter the water supply system. The objective of this study was to evaluate bacteriological and physicochemical quality of water supply system in Welkite Town, southwest Ethiopia. The water samples were examined on site for total coliform and thermo tolerant coliform using membrane filtration method. Raw water samples were positive for total coliform and thermo tolerant coliform, and there was high bacteriological load in Bojebar spring source which is total coliform: 16 cfu/100 ml, thermo tolerant coliform: 8 cfu/100 ml and in balancing reservoir, there was no detection for both total coliform and thermo tolerant coliform, whereas total coliform and thermo tolerant coliform were detected in the pipeline (counted as 6 and 1 cfu/100 ml, respectively). Similarly, in the service reservoir, the result indicated 9 and 1 cfu/100 ml for both total coliforms and thermo tolerant coliforms, respectively. On the other hand, temperature at all sampling sites was above the permissible limit set by World Health Organization but pH, electrical conductivity, turbidity, total hardness and total dissolved solids were all within the permissible limit set by World Health Organization. The free chlorine residual was 0.02, 0.84, 0.67, 0.48, 0.45 and 0.1 mg/l at six different sampling points, respectively, while the sanitary survey showed that cumulative risk score of all water supply systems was 27.2, 54.5, 90.09, 45.5 and 64% from the source to distribution, respectively.

Key words: Bacteriological parameters, sanitary survey, total coliform, thermo tolerant coliform.