Performance and membrane fouling mitigation for bio-treated coking wastewater treatment via membrane distillation: Effect of pre-treatment

Abstract

A large amount of coking wastewater is generated from the coal coking industry in China. As the coking wastewater containing high concentration of hazardous substances is harmful to the environment and health, it is necessary to be properly treated before being discharged. In this work, direct contact membrane distillation (DCMD) is explored to deeply treat the real bio-treated coking wastewater (BCW). DCMD system performance and membrane fouling are evaluated. Results showed that the serious membrane fouling caused by the brown fulvic and humic acid-like organics in the BCW occurred, resulting in permeate flux decline sharply. Various pre-treatment approaches including coagulation, ozonation and electrocoagulation (EC) were selected to alleviate membrane fouling. It was noteworthy that the long-time steady flux and low permeate conductivity was kept during DCMD filtration of the BCW pre-treated by EC. Moreover, the membrane surface remained clean at the conclusion of the DCMD experiment. In contrast, permeate flux declined quickly due to membrane pores plugging during DCMD treatment of the BCW pre-treated via ozonation. More pollutants penetrated into the permeate, which was caused by the removal of humic acid from the fouling layer during DCMD treatment of the BCW pre-treated via coagulation. Our work suggested that DCMD process combined with EC can be used as an advanced treatment to treat the BCW effectively.