الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Direct filtration system has been employed as alternative to the conventional treatment system for treating surface water. The main advantage of a direct filtration plant over a conventional treatment plant is saving of capital costs, chemical costs and operation and maintenance costs of approximately 20-30 percent. Declining rate filtration is a new method of controlling the flow rate in filters .In the same time deep bed filters are employed in several places in the world. A treatment plant employing direct filtration with a declining rate mode of operation as well as deep bed filter was constructed in more then 80 location all over Egypt. In the main time constant rate two stage direct filtration treatment plant were also employed in Egypt. The main problem of water purification process in Egypt is to provide a system with highest possible efficiency and at the same time the lowest possible cost. In case of presence of 120 direct filtration plant in Egypt, so from this was the main purpose of this study is evaluation the new direct filtration technique widely used in Egypt. Also a comparison between the declining rate direct filtration system and constant rate direct filtration system as operating systems under Egyptian conditions Even though two stage direct filtration system is more efficient than the one stage direct filtration in dealing with Nile River water, the one stage direct filtration system is more economic . The declining rate one stage direct filtration system decreases the quantity of wash water and the head loss of water and it proves higher operation efficiency than constant rate two stage direct filtration system.