Forward osmosis coupled with electrochemical oxidation for treatment of reverse osmosis concentrate from coal chemical industry

During the forward osmosis (FO) treatment of the chemically softened reverse osmosis concentrate sourced from the coal chemical industry, organic fouling occurred and seriously reduced the FO flux. To address this issue, electrochemical oxidation (EO) was coupled with FO for organics removal and water reclamation. Under the effect of direct oxidation and indirect oxidation mediated by center dot OH and active chlorine, COD was removed by about 90 % at 20 mA/cm(2), significantly slowing down the FO flux decline. According to excitation-emission matrix fluorescence spectroscopy (EEMs) and gel permeation chromatography (GPC), the removal of fluorescent organics was higher than 95 %, while 62.6 %, 52.2 %, and 13.0 % for large molecules (>5 kDa), medium molecules (1-5 kDa), and small molecules (<1 kDa), respectively. As shown by the economic analysis, EO-FO (EO pretreatment followed by FO) was more economically feasible than FO-EO (FO preconcentration followed by EO), mainly because of the serious fouling and large investment of cleaning chemicals in FO-EO. This study proves the feasibility of EO-FO for an enhanced overall performance of water reclamation and organics removal during high-salinity wastewater treatment, providing meaningful insights into achieving the goal of zero liquid discharge.