الفهرس 
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Abstract
One of the most harmful water contaminants is the natural organic matter (NOM) which can be defined as a heterogeneous mixture of naturally occurring organic compounds existing abundantly in natural waters. It mainly originates from living and dead plants, animals and microorganisms. Generally, NOM influences water treatment processes such as coagulation, oxidation, adsorption, and membrane filtration in a significant manner. It additionally causes aesthetic problems like color, taste and odor. Through the last decades, increasing NOM concentration levels in water sources have been recognized in many countries because of several issues like global warming, changes in soil acidification, increased drought severity and more intensive precipitation events. Along with the trend of increasing NOM concentration, the character of NOM can alter with source and time (season). The existence of NOM in water sets challenges to the drinking water industry and water treatment facilities in terms of operational optimization and proper process design and control. The work conducted in this thesis is directed towards investigating the effect of alum doses on the performance of deep bed sand filters in removing NOM accompanied with turbidity from water under different operational conditions. These conditions represent in water pH, rate of filtration, and NOM concentration level. Experiments are held in the Laboratory of Sanitary Engineering, Faculty of Engineering, Mansoura University using a specially manufactured pilot plant in order to determine the optimum operation conditions for the removal of NOM. Finally, it has been found that the removal of high concentrations of NOM in water is recommended to be achieved via using rate of filtrations up to moderate values while lower concentrations of NOM are recommended to be removed through slow rate of filtrations only. In regard to the effect of the alum dose on NOM removal, the current-employed deep bed sand filter is found to be able to reduce the NOM concentrations in the effluent water to nearly onethird or less. Additionally, the highest alum dose among the proposed ones (15 mg/L) is suitable to remove the most NOM in the case of low and high influent NOM concentrations. Yet, an alum dose of only 5 mg/L is sufficient to remove the most NOM in the case of moderate influent NOM. Moreover, the acidity of influent water plays a vital role in the presence of NOM particles in the effluent one. It has been demonstrated that the optimum pH value of influent water in the studied samples is 5 followed by 6 and 7, respectively.