Thirteenth International Water Technology Conference, IWTC 13 2009, Hurghada, Egypt 169 TREATMENT OF GREATER-ZAB WATER BY DIRECT FILTRATION Shuokr Q. Aziz Department of Civil Engineering, College of Engineering, University of Salahaddin - Arbil, Kurdistan region, Iraq ABSTRACT In this research, a water treatment plant is designed to treat Greater-Zab River water by direct filtration. Direct filtration comprises of intakes, coagulation, flocculation, and filtration is not preceded by in-plant sedimentation of flocculated water. To ensure which season is suitable for using direct filtration process; turbidity values of Greater- Zab water recorded throughout fourteen months, October 2004 to May 2005 and May 2006 to October 2006. Proposed treatment-plant units are designed and summary of design are outlined. Cost analysis of conventional treatment-plants and direct filtration discussed. Keywords: Direct filtration of water, Greater-Zab River, and turbidity INTRODUCTION A primary requisite for good health is an adequate supply of water that is of satisfactory sanitary quality. It is also important that the water be attractive and palatable to induce its use; otherwise, water of doubtful quality from nearby unprotected water sources may be used [1]. Natural waters are rarely of satisfactory quality for human consumption or industrial use and nearly always need to be treated. The level of treatment required will depend on how acceptable the natural water is. Raw freshwater is abstracted from rivers, lakes or underground sources and treat to standards acceptable for human consumption or industrial requirements [2]. Potable water is most conventionally classified as to its source, that is, groundwater or surface water. Generally, groundwater is uncontaminated but may contain aesthetically or economically undesirable impurities. Surface water must be considered to be contaminated with bacteria, viruses, or inorganic substances which could present a health hazard [3]. Generally, in Iraqi Kurdistan both surface and ground water sources are used for different uses. Also in Arbil City both water sources are used for drinking and domestic uses: 1) Surface water, Greater-Zab lie on the North West of Arbil City, Figures1 and 2. It is the only surface water source for drinking and other uses. 2) Groundwater, there are more than 416 drilled wells spread over entire city [4].