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

Abstract

Debasu Damtie, Mengistu Endris, Yifokir Tefera, Yabutani Tomoki, Yohei Yamada, Afework Kassu

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 to 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 a turbidity meter, pH meter, and thermometer, respectively. Arsenic, chlorine, Cr6+, NO2, NO3 andresidual chlorine were determined by the colorimetric methods and rapid kits using disruptive pattern material apparatus (Kyoritsu chemical-check Lab., Corp. Japan). Coliforms and Vibrio parahemolyticuswere tested by rapid microbiological test strips (Sankori coliform and Sankori V. parahaemolyticus) following appropriate standard procedure. Consumer’s assessment was also conducted using a 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 ± 5.75 standard deviation nephelometric turbidity unit, temperature 21.34 ± 3.68°C, 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 World Health Organization 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 V. 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 were potential risk to public health. Therefore, regular quality monitoring and frequent water treatment in the study area is mandatory.