Several research efforts have been devoted to improve the efficiency of coagulation–flocculation process, a basic and essential treatment technique both for water or wastewater treatment facilities, especially for those handling hazardous or toxic liquid wastes (e.g. tanneries, metal plating, etc.) or difficult to treat low-strength wastewaters.
Water in its natural and waste water forms includes small particulates. In water, those particulates with the same charge are suspended into a colloid (a mixture with properties between a fine suspension and a solution). The repulsion process–the physical property of particles with the same charge (i.e., negative and negative) repelling each other–stops the particulates from combining into a settled form. Coagulation water treatment applies chemicals to assist water particulates in combining together. When particulates are aggregated, they can be more easily removed from the treated water.
The Laboratory of General & Inorganic Chemical Technology (LGICT) of the Chemistry Department at Aristotle University, has recently developed innovative chemicals-coagulants, which include mostly inorganic compounds of polymerized ferrum (polyferric sulfate, PFS, Fig.1 ) as well as composite modified flocculants ferrum silicates (PFSiS), or organic polyelectrolytes (PFS-PAA). The research team has proved that these pre-polymerised coagulants exhibit a significantly better coagulation performance than the conventional non-polymerised one, i.e. ferric sulphate, mainly due to their high cationic charge and increased molecular size.