Efficiency of Hybrid Process of Coagulation/Flocculation Followed by Membrane Filtration for the Treatment of Synthetic Vegetable Oil Refinery Wastewater

Abstract

New regulations in environment protection and increasing market demands for “green” companies are forcing the industry to consider finding new and sustainable methods of wastewater treatment. The technological process of wastewater treatment may consist of many processing stages, depending on the characteristics of the raw wastewater and the required quality of the treated wastewater. Therefore, this study aimed to investigate the efficiency of hybrid treatment process using coagulation/flocculation, cross-flow ultrafiltration, and/or in dead-end filtration producing a final effluent conforming to regulatory standards with regard to chemical oxygen demand, total organic carbon, and turbidity loads. Treatment experiments were conducted using soya oil/in water emulsions. Coagulation/flocculation experiments were conducted using jar test protocol. The cross-flow ultrafiltration experiments were carried out using tubular ceramic membranes with a membrane cut-off of about 150 kDa and under transmembrane pressure equal to 1.25 bars, whereas dead-end filtration experiments were performed using different pore sizes of flat membrane as preliminary work to devote to CFF in terms of screening of the most adequate membrane pore size. The membrane permeability was investigated as a function of operation time and volumetric concentration ratio in order to achieve a cost-effective process. The results showed that ultrafiltration is a convenient technique as a secondary step after coagulation/flocculation, while the removal rates of COD, TOC, and turbidity reached 98%, 99%, and 100%, respectively. The obtained results confirm a promising application of hybrid treatment process combining CF and membrane filtration involving a ceramic ultrafiltration membrane in the treatment of edible oily wastewater.