Efficiency Evaluation of a Conventional Drinking Water Treatment plant Units: A Case of Jimma Town

Abstract

Drinking water supplied to the community passes through a series of treatment processes (depending on their sources) before they reach to the end users. For surface water sources, conventional drinking water treatment technology is widely applied. Jimma city is one of the cities in Ethiopia which require well treated and enough amount of water. This city has conventional treatment plant which was constructed and starts function in 2015 with a design capacity of 12,196m 3 /d. Therefore, the objective of this study was to assess the efficiency of the treatment plant in each treatment unit to provide good quality and enough amount of well treated water to the town. But due to urbanization and population growth there was a limitation in providing good quality and enough amount of drinking water. Different methods were used during the study period: laboratory used to measure and evaluate physical, chemical and biological parameter of the water; providing questions and visual observation to determine the management and control practice The design capacity of the unit processes was evaluated by considering current peak water demand and selecting appropriate loading rates as basic criteria and the quantity of water provided to the institutions was investigated by conducting data from the institution and Jimma city water supply office and analysed by arithmetic method and evaluated with the forecasted demand from the design document. The analyses of the findings indicate that the plant has no capacity to treat adequate water demanded with current peak daily demand of 19912.76m3 /d. Water parameter (physical, chemical and biological) result: biological result show that the raw water have contaminated by bacteria both fecal and total coliform bacteria measured after disinfection was (FC=18mg/L and TC=61mg/L.)the rest physical and chemical result measured after disinfection was: pH (7.13), turbidity(0.4NTU), temperature (21.9oC), E.cond (119µs/cm), TDS (60mg/L), total hardness(32mg/L), Mg2+ (18mg/L), Ca2+ (14mg/L), alkalinity (500mg/L), Fe2+(0.01mg/L), Mn2+(0mg/L), SO4 2- ( 10mg/L), NH4 + (0mg/L), Cl- (4.99), NO3 - (5.978mg/l). All chemical and physical parameters were under the permissible limit of WHO standard except alkalinity with a result equal to the maximum standard kept by WHO and the biological parameter was totally fell the standard. The analysed management and control practise was poor. Water was not adequately available in all schools in the city. Design, operational and control factors were identified as major causes for the weak performance of the plant