Effect of flocculation as a pretreatment to photocatalysis in the removal of organic matter from wastewater

Effects of different flocculants (chloride-based salts and ferric and ferrous salts) and initial organic concentration of wastewater on flocculation-photocatalysis hybrid process were investigated. Titanium dioxide (TiO2) adsorption alone, flocculation alone, flocculation followed by TiO2 adsorption, photocatalysis alone, and flocculation followed by photocatalysis removed 60, 72, 80, 85, and 92% of dissolved organic matter (DOC), respectively. The effect of photo-Fenton reaction in removing organic matter was found to be marginal on the flocculation-photocatalysis hybrid system. The organic removal with the flocculation-photocatalysis hybrid system showed similar results for different flocculants such as chloride-based salts, ferric and ferrous salts and there is no comparative beneficial effect. Flocculation followed by photocatalysis removed up to 92% of organic matter. Different initial concentrations of organic matter were significantly reduced by flocculation to a low level before loading to the photocatalysis process. (C) 2007 Elsevier B.V. All rights reserved.