Treatment of public water supply is an indispensable element in providing safe drinking water and to minimize the prevalence of waterborne diseases. However the efficiency of treatment plants was not known in Ethiopia. This study aims to determine drinking water quality and the efficiency of treatment plants in Southwest Ethiopia. Eighty four water samples were collected from the sources to household taps during dry and rainy seasons. A pre-tested and calibrated multi-parameter probe and turbidity meter were used to measure on the spot. Samples were transported at 4 °C and analyzed according to standard methods and procedures. The majority (87.4%) of physicochemical parameters were in compliance with the WHO standard. However, free residual chlorine, coliform and fluoride were not within the recommended limits. WQI of Agaro and Metu were in good category; whereas Jimma water was in poor category. The log removal value (LRV) and efficiency of treatment plants were 73.6%, 48.4% and 74.1% effective in overall pollutant removal in Jimma, Agaro and Metu, respectively. The treatment plants were still technologically appropriate to deliver safe water to the public, but focusing on technical skills on water treatment and quality monitoring may improve the observed negative findings.

Keywords: Physicochemical Studies; Treatment Plant; Water Quality; WQI;