Performance Evaluation of Drinking Water Treatment Plant (case Study: Gambella town Drinking water Treatment Plant)

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Addis Ababauniversity


The conventional water treatment plant, especially in developing countries, faces major challenges in terms of assessing its operation and performance due to inappropriate technologies, insufficient equipment and deficiency in skilled expertise. Simple but efficient technologies are therefore necessary for reasonable evaluation of the daily performance of the plant. Turbidity is thought of as a convenient surrogate to give favorable indication of the biological and physical quality of the treated water thus by extension provide a fair gauge of the performance of the treatment plant with respect to water purification. Besides, it is fairly simple to measure, cheap and can easily be understood by the operators. In this study the performance of Gambella town water treatment plant was assessed. The study was conducted by assessing unit process capability, design, operation and maintenance potential to meet optimized goals. From results of the assessments, root factors limiting optimum performance were identified and improvement options were proposed. Major unit processes were evaluated to project their design capabilities to meet current peak water demand by selecting appropriate loading rates as basis criteria. The results of the assessment found that all units had the capability to satisfactorily treat water at peak daily demand of 2000 m3/day. The study assessed turbidity performances of sedimentation and filtration units by setting optimized turbidity goals. The assessment results indicated that, settled water turbidity was measured less than 10 NTU. And filter turbidity spike of 6.5 NTU following backwash with a reduction to 0.6 NTU after one hour was observed. Generally optimized performance goals were not being achieved. This indicated high risk of microbial pathogens that could pass the filtration barriers in the finished water. Jar test experiments were conducted to evaluate the effectiveness of Aluminum Sulphate (recently used by the treatment plant), Ferric chloride and Ferric Sulphate by comparing the optimum dose at optimum pH for highest turbidity removal and relative costs. From the jar test results Aluminum Sulphate was found to be the effective chemical with 45 mg/l optimum dose at pH 7.1 and the treatment plant was recommended to continue using Aluminum Sulphate at the optimum dose for the raw water characteristics during the evaluation period. Treated water samples were collected from the clear-water well to test 14 water quality parameters according to the standard methods for water and waste water examinations. The collected samples were intended to show the x characteristics of the finished water only during the evaluation period. The samples were analyzed at the laboratory of GWTP and results were compared with WHO standards and guidelines for drinking water. Results of the analysis showed that all of the measured parameters were within the acceptable range. In the assessment of factors limiting performance of the treatment plant; major factors were categorized as design, operational and maintenance. No single factor was responsible for poor plant performance, although in general the study found that all factors influence the plant’s ability to work properly. Some of the primary operational problems and the intake structure’s adequacy significantly affected performance. Operational factors were found to have the highest rank. This finding, coupled with the fact that the plant had adequate capability, indicates that improving process control could significantly improve performance



: Gambella town Drinking