Assessment Of Selected Faecal Indicator Bacteria (Escherichia Coli And Enterococci) Load In Drinking Water Supply Of Ambo Town, West Showa Zone Of Oromia, Ethiopia

Abstract

Fecal indicator bacteria (FIB) such as Escherichia coli (E. coli) and Enterococcus spp. occur in high concentrations in the gut of humans and other warm-blooded animals. They can serve as biological indicator for contamination of water. In this study, selected physio-chemical parameters and FBI (E.coli and Enterococci) load were studied to evaluate quality of drinking water supply of Ambo Town, Ethiopia. Standard methods were employed to investigate the studied physicochemical parameters including temperature, pH, electrical conductivity (EC) and dissolved oxygen (DO). The bacteriological concentration/load was determined using filtration method and risk categories were also performed according to the WHO 1997 classification and color-code scheme. The physicochemical analysis results showed that the mean (minimum – maximum) values of temperature, pH, EC, DO are 21(18.3-23)°C and 18.8(17-21)°C, 7.44(7.08- 7.87) and 7.38 (7.05-7.87), 101.1(88.9-120) µs/cm and 111.3(99.2-169) µs/cm, 7.6(6.6-8.78) mg/l and 7.5(6.8-8.2) mg/l in for dry and wet seasons, respectively. The measured mean (minimum – maximum) of E.coli in dry and rainy (wet) seasons for raw water samples were 164 (112 – 217) CFU/100ml and 327 (309 – 340) CFU/100ml, respectively, while for Enterococci spp. the observed load were 233 (214 – 274) CFU/100ml and 327 (202 – 451) CFU/100ml respectively for dry and rainy season’s samples. Similarly, for the treated water samples the observed mean (minimum – maximum) load for E. coli were 8.96 (0.00 – 10.00) CFU/100ml for dry season and 25.1 (0.0 – 33.0) CFU/100ml for rainy season, while for Enterococci spp. 13.0 (0.0 – 19.0) CFU/100ml and 27.8 (0.0 – 47.0) CFU/100ml for dry and rainy seasons water samples, respectively. As the risk assessment result shows the water samples collected from the majority of the sampling sites (85%) were laid in the range of green color coding with low risk. Whereas (5%) and (10%) were in color of orange with high risk and yellow with inter-mediate risk, respectively. In both the wet and dry seasons, there is a substantial link/correlation between Enterococci and E.coli load