The present drinking water purification system in Egypt uses surface water as a raw water supply without a preliminary filtration process. On the other hand, chlorine gas is added as a disinfectant agent in two steps, pre- and post-chlorination. Due to these reasons most of water treatment plants suffer low filtering effectiveness and produce the trihalomethane (THM) species as a chlorination by-product. The Ismailia Canal represents the most distal downstream of the main Nile River. Thus its water contains all the proceeded pollutants discharged into the Nile. In addition, the downstream reaches of the canal act as an agricultural drain during the closing period of the High Dam gates in January and February every year. Moreover, the wide industrial zone along the upstream course of the canal enriches the canal water with high concentrations of heavy metals. The obtained results indicate that the canal gains up to 24.06x10(6) m(3) of water from the surrounding shallow aquifer during the closing period of the High Dam gates, while during the rest of the year, the canal acts as an influent stream losing about 99.6x10(6) m(3) of its water budget. The reduction of total organic carbon (TOC) and suspended particulate matters (SPMs) should be one of the central goals of any treatment plan to avoid the disinfectants by-products. The combination of sedimentation basins, gravel pre-filtration and slow sand filtration, and underground passage with microbiological oxidation-reduction and adsorption criteria showed good removal of parasites and bacteria and complete elimination of TOC, SPM and heavy metals. Moreover, it reduces the use of disinfectants chemicals and lowers the treatment costs. However, this purification system under the arid climate prevailing in Egypt should be tested and modified prior to application.
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