Esayas, Gebreyouhannes (PhD)Obsa, Bayissa2021-04-022023-11-282021-04-022023-11-282015-06http://etd.aau.edu.et/handle/12345678/25920In modern water supply treatment plant high rate settler units achieve effective settling process than conventional sedimentation tank. This high rate settler can be considered during the new sedimentation tank construction and also existing sedimentation tanks can be modified by including such units. This study was aimed at the assessment and evaluation of the application of high rate tube settlers in the case of Legadadi Water Supply Treatment plant by two main methods. The first one is by comparing and evaluating the performance of settling process of the sedimentation tank that the high rate tube settler is provided for it and the one without it. The second method contained the pilot scale experiment developed at this treatment plant to evaluate and asses the performance of the existing one. The comparatives and experimental results concluded optimistically that the high rate tube settler can provide better performance than that of the conventional sedimentation tanks. The comparative results indicates that the performance in production efficiency increase by 34.5% and the effects of HRTS on filtration units saves 35.11% water use for filter back washing. Additionally the pilot experimental result due to high rate tube settlers’ shows that the production efficiency increased by 35.30%, detention time decreased by 33.7%, turbidity reduction is increased by 76.65% and the chemical amount required is reduced significantly. Therefore; from the results of the two study it is possible to conclude that the application of high rate tube settlers provides effective sedimentation process ,positive effect on filtration unit, and cost effective in(structural and land cost of sedimentation tank, chemical cost and other operational costs). The results of the study offered to recommend that the Legadadi Water Supply treatment can upgrade and improve the efficiency of process relative to the pilot scale results and; Other Water Supply institutions have to use this high rate tube settler to gain all important advantageous to be achieved.en-USLegadadi Water Supply TreatmentHigh Rate Tube SettlersAddis Ababa EthiopiaThesis