Improving performance of dynamic membrane assisted by electrocoagulation for treatment of oily wastewater: Effect of electrolytic conditions

A dynamic membrane/electrocoagulation hybrid system, with precoating of a microfiltration ceramic membrane using Kaolin clay, was investigated with respect to membrane fouling mitigation and oil removal during the treatment of oily wastewater. The performances between the ceramic membrane and dynamic membrane employed for the electrocoagulation hybrid systems were compared. The results showed that dynamic membrane/electrocoagulation always achieved greater efficiencies of membrane fouling alleviation due to the reduction of irreversible and reversible resistance by dynamic layer and electrocoagulation, respectively. Since the aluminum anode seemed more inclined to form a looser layer, the performance of dynamic membrane/ electrocoagulation was better using iron anode than aluminum one. The normalized fluxes and oil removal rates of effluent increased with the rise of current density and decline of initial pH. In low range of current density from 4 mA·cm−2 to 30 mA·cm−2, this variation trend was more obvious. The permeate flux and oil removal rate were obviously high at the initial of pH 3.2 owing to the result of demulsification. A superior efficiency on oil removal and mitigation of dynamic membrane fouling was presented from oily wastewater treatment, revealing that electrocoagulation is a promising coupling technique with dynamic membrane for wastewater treatment. © 2015 Elsevier B.V. All rights reserved.

A Kaolin dynamic membrane/electrocoagulation hybrid system was investigated with respect to membrane fouling mitigation and oil removal during the treatment of oily wastewater. The performances between the ceramic membrane and dynamic membrane employed for the electrocoagulation hybrid systems were compared. The results showed that dynamic membrane/electrocoagulation always achieved greater efficiencies of membrane fouling alleviation than electrocoagulation/ceramic membrane, ceramic membrane alone and dynamic membrane alone. Since the aluminum anode seemed more inclined to form a looser layer, the performance of dynamic membrane/electrocoagulation was better using iron anode than the aluminum one. The oil-gel layer covering the surface of the dynamic membrane using aluminum anode was more compacted than that using the iron anode. The normalized fluxes and oil removal rates of the effluent increased with the rise of the current density and decrease of the initial pH. In the low current density range from 4 mA·cm−2 to 30 mA·cm−2, these variation characteristics were more obvious. The normalized flux and oil removal rate of the effluent were much greater at an initial of pH 3.2 as compared to pH 6.2, 7.1 and 9.7 as a result of demulsification caused by soluble cations Fe3+, Fe(OH)2+ and Fe(OH)+. In the hybrid process of electrocoagulation/dy2 namic membrane, the maximum normalized fluxes of 34.2%, and oil removal rates of the effluent and permeate of 65% and 98.5% have been observed, respectively. The electrocoagulation can effectively reduce the reversible resistance, and the dynamic layer was especially useful for the reduction of irreversible resistance. The reversible membrane fouling was the primary cause of decline of the permeate flux. Acknowledgment The authors would like to acknowledge financial support from the Research Projects of nature science foundation of Jiangxi Province (Project No. 20142BAB203019) and the Research Projects of Jiujiang University (Project No. 2014KJ14).