1 PSiFAC – POLY-ALUMINUM-FERRIC-SILICATE-CHLORIDE: SYNTHESIS AND COAGULATION PERFORMANCE OF A NOVEL COMPOSITE COAGULANT IN WATER AND WASTEWATER TREATMENT A. Tolkou 1 , A. Zouboulis 1 , P. Samaras 2 1 Laboratory of General & Inorganic Chemical Technology, Department of Chemistry, Aristotle University of Thessaloniki, GR-54124, Thessaloniki 2 Laboratory of Water & Wastewater Technologies, Department of Food Technology, Alexander Technological Education Institute of Thessaloniki, GR-57400 Thessaloniki E-mail: tolkatha@chem.auth.gr , zoubouli@chem.auth.gr , samaras@food.teithe.gr ABSTARCT The aim of this work was the study of the combination of an inorganic pre-polymerized coagulant (PACl) with ferric species and polysilicic acid in various Al/Fe/Si and OH/Al molar ratios, and two polymerization techniques for the production of a unique reagent representing a coagulant, more efficient than commercial PACl-18 and laboratory prepared PACl lab for water or wastewater treatment. A number of coagulants were prepared and were examined by jar tests for the treatment of simulated water; turbidity and UV 254nm absorbance were measured in the treated water. PSiFAC 1.5:10:15 prepared by co-polymerization was found to be the most efficient coagulant from all the tested compounds. Low coagulant doses, about 2 mg/L were required for the reduction of turbidity values to lower than 1 NTU; furthermore, PSiFAC 1.5:10:15 resulted in very low residual aluminum concentration of about 140µg Al/L. The most effective coagulant obtained was also used for the treatment of tannery wastewater to evaluate their performance and it was observed that high turbidity removal was obtained at doses of about 100 mg/L. Keywords: water and wastewater treatment, composite coagulants; poly-aluminum-ferric- silicate-chloride coagulants, coagulation, turbidity removal. 1. INTRODUCTION Water and Wastewater management encompasses a broad range of efforts that promote effective and responsible water use, treatment, and disposal. Coagulation-Flocculation is an essential part of several water and wastewater treatment operations, as advanced pretreatment process to flocculate colloidal and dissolved organics. The Inorganic Polymeric Flocculants (IPFs), or pre-polymerized coagulants, such as polyaluminum chloride (PACl) [1], represent a relatively type of coagulation reagents, which were developed in order to increase the efficiency of coagulation-flocculation process. By introducing metal ions into polymerized silicic acid solution [2], the molecular weight of the product was increased and the corresponding stability and coagulation performance were further improved. Extensive studies on polysilicate coagulant combined with ferric salt and aluminum salt have been conducted by several researchers all over the world [3-13]. Zouboulis and Tzoupanos [9, 10], systematically examined several silica-based polyaluminum chloride derivatives, leading to the following optimized conditions for their preparation, according to the respective coagulation performance data: OH/Al ratio 1.5–2, Al/Si ratio 10–15, whereas co- polymerization should be preferred for the coagulant preparation. Today, there is a prompt need for the development of new PAC-based coagulants such as poly-aluminum-ferric-silicate-chloride (made of aluminum, ferric and silicate) to improve the coagulation performance. The ferric salts can generate thicker and heavier flocs than