Assessment of microbiological and physico-chemical quality of drinking water in North Gondar Zone, Northwest Ethiopia

Abstract

Introduction: Assessing the microbiological and physico-chemical quality of drinking water sources is important to protect public health. Little is known about the microbiological and physico-chemical quality of drinking water in North Gondar Zone. Therefore, this study was aimed to assess the microbiological and physico-chemical quality of drinking water sources in North Gondar Zone, Northwest Ethiopia. Methods: A cross-sectional study was conducted from April-May 2014 in seven districts (Chilga, Debark, Dabat, Dembia, Gondar Town, Gondar Zuria and Wogera) in North Gondar. The physico-chemical and microbiological quality of 71 drinking water samples were determined following the standard procedure. Turbidity, pH, and temperature were measured using turbidity meter, pH meter and thermometer respectively. Arsenic, chlorine, Cr6+, NO2, NO3 and residual chlorine were determined by the colorimetric methods and rapid kits using DPM apparatus (Kyoritsu chemical-check Lab., Corp. Japan). Coliforms and Vibrio parahemolyticus were tested by rapid microbiological test strips (Sankori coliform and SankoriVibrio parahaemolyticus) following appropriate standard procedure. Consumers assessment was also conducted using questionnaire about the water sources. Data were entered and analyzed using SPSS version 20 software. Results: The physico-chemical and microbiological quality of 71 water samples (tap n=29, spring n=15 and well n=27) were assessed. The mean turbidity of water samples was 19.35 + 5.75SD nephlometric turbidity unit (NTU), temperature 21.34+3.68 oc, pH 6.88+0.6, nitrate 10.02 + 8.72 mg/l, nitrite 0.33+0.64 mg/l, residual chlorine 0.01 + 0.06 mg/l, arsenic 0.2+0.00 mg/l and chromium 0.51+0.01 mg/l. Almost all samples were complying with the WHO acceptable range for nitrate arsenic and chromium among the physico-chemical parameters. However, turbidity was found to be unacceptably high in 21 (29.6%) samples, pH was unacceptably low in 26 (36.6%) of the samples and residual chlorine was unacceptably low in 69 (97.2%) of the samples. The majority of samples (n=46; 64.8%) had coliforms and 12 (16.9%) had Vibrio parahemolyticus. Conclusion: Most of the physical and chemical parameters measured were within the recommended range except turbidity and residual chlorine. However, the majorities of drinking water samples were found to be contaminated and are potential risk to public health. Therefore, regular quality monitoring and frequent water treatment in the study area is mandatory.