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This study investigated the impact of conventional pre-treatment on the fouling potential ofseawater. The conventional treatment train consisted of coagulation (ferric chloride as thecoagulant) followed by rapid dual media filtration (sand/anthracite). The impact of post-chlorination(sodium hypochlorite) was also studied. Laboratory experiments were carried out onAtlantic Ocean seawater and some pilot tests were performed on Mediterranean Sea water.Several parameters were monitored both in raw and treated waters including total organiccarbon, total nitrogen and phytoplankton pigments (HPLC analysis). Microorganisms(picophytoplanktonic cells and bacteria) were also analyzed by flow cytometry. Residualoxidant and trihalomethanes were analyzed in the chlorinated water as a function of time.Membrane fouling tests were performed on the pretreated waters using a cellulose regeneratedultrafiltration membrane (MWCO 100 kDa) in dead-end mode. Results showed that aboutof the micro-organism population were removed by coagulation and dual mediafiltration. On the contrary, total organic carbon (TOC) and TN removals were almost insignificant. The influence ofcoagulant dose and pH studied during pilot scale experiments showed minor effect ofcoagulant dose and higher microorganism and particle removal at low pH (pH 5.9). Themembrane fouling potential was significantly reduced after direct filtration. The addition ofchlorine (sodium hypochlorite) led to the formation of bromoform as the dominant trihalomethane (THM) byproduct.Our results showed that THM precursors were significantly reduced after directfiltration. Also, post chlorination slightly reduced ultrafiltration (UF) membrane fouling and eliminated theremaining picophytoplanktonic cells. Includes 7 references, tables, figures.

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Edition: Vol. - No. Published: 03/01/2005 Number of Pages: 13File Size: 1 file , 480 KB