Investigation of Drinking Water Quality from Source to Point of Distribution :-(The Case of Gimbi Town, in Oromia Regional State of Ethiopia).

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Addis Ababa University


This research focuses on the investigation of the existing main drinking water quality of Gimbi town, which is located in Western Ethiopia, from the source to points of distribution in relation to safety and acceptability for users concerning water quality parameters. Efforts were also made to identify the relationship between the residual chlorine and pressure in the gravity distribution of the water supply network systems. The town gets its water supply from a treatment plant, which is established on Gafere River. Two subsequent methods were used to achieve these objectives. The first method involved the collection of samples from different locations of the study area followed by laboratory analyses, and the other method involved the use of simulation models such as EPANET Software to identify the pressure effect on residual chlorine in the water supply gravity distribution system. The analyzed water sample parameters include physico-chemical and bacteriological parameters. For bacteriological analyses, the whole 30 representative samples were randomly selected from sensitive areas for expected pollution such as raw water, treatment plant, service reservoir, water points, ends of pipe network, and customer point of use, and 17 samples were used for physico-chemical analyses. The results were analysed and interpreted by using Microsoft excel spread sheet, Global mapper and suffer software. The results obtained show that except iron, residual chlorine and pH, the rest all parameters were within the World Health Organization (WHO) permissible limit. The results for iron concentration were found between the range of 0.6-2.5 mg/l, the majority of samples have pH values between 6.01-6.45 (only two samples have pH values of 6.5, which is the WHO minimum permissible limit), and 30% of tested samples have residual chlorine below the WHO minimum permissible limit (0.2 mg/L). All the remaining physico-chemical parameters and Biochemical Oxygen Demands were safe and within the range of acceptable drinking water quality. By contrast, all parameters were found within the range of the Ethiopia recommended values permissible limit for drinking water quality. However, regarding the aesthetic and acceptability of physical parameters like colour and turbidity were above the maximum permissible limit of both WHO and Ethiopian recommended guideline for permissible limit. Although further research is required to draw ultimate conclusions, at this point it can be considered that there is no health significance on the users concerning the physico-chemical parameters. Similarly, the result of bacteriological analyses indicated that in most of the samples low risk were observed after treatment plant except for sample-7 and sample-12 due to high turbidity, longer residence time of the water in the system, and the presence of total coliforms expressed by Too Numerous To Count (TNTC). To overcome these problems regular chlorination is recommended. The simulation results showed that the pressure has inverse relationship with the residual chlorine in the gravity distribution systems of the networks KEY WORDS: Water quality parameters, WHO standards, Water borne diseases, Pressure, Residual chlorine, Gimbi,Oromia, Ethiopia.



Water quality parameters; WHO standards; Water borne diseases; Pressur; Residual chlorine; Gimbi;Oromia; Ethiopia