Treatment of nanofiltration concentrate of landfill leachate using advanced oxidation processes incorporated with bioaugmentation

Advanced oxidation processes have been broadly applied in wastewater treatment, but few studies have focused on its degradative effect on refractory organic contaminants in membrane concentrates of landfill leachate. In this study, the treatment effects of advanced oxidation processes including electrocoagulation (EC), ozone (OZ), anodic oxidation (AO) and electro-Fenton (EF) incorporated with genetically engineered nitrifying bacteria Rhodococcus erythropolis expressing Nirs and AMO (rRho-NM) on nanofiltration concentrate (NFC) of old landfill leachate were investigated in a lab-scale experiment. The results showed that advanced oxidation processes degraded the refractory organic contaminants including coagulation-resistant substances (CRS), humic acid (HA), fulvic acid (FvA), macro molecular organics (MMOs) and benzene ring compounds (BRCs) and increased the biodegradability in NFC of old landfill leachate. Compared to activated sludge (AS), rRho-NM exhibited an excellent removal performance for total organic carbon (TOC), ammonia nitrogen (NH₄–N), total nitrogen (TN), biochemical oxygen demand (BOD) and chemical oxygen demand (COD) for advanced oxidation processes-treated NFC of old landfill leachate. Advanced oxidation processes incorporated with bioaugmentation demonstrated an outstanding degradation performance for removing refractory organic contaminants, TOC, NH₄–N, TN, BOD, COD and heavy metal in NFC of old landfill leachate. In addition, OZ incorporated with rRho-NM (OZ-rRho-NM) showed the optimal removal efficacy in reduction of refractory organic contaminants, TOC, NH₄–N, TN, BOD and COD, the shortest hydraulic retention time (HRT) and the minimum energy consumption in NFC of landfill leachate. Furthermore, the cheapest treatment cost for NFC could be achieved by EC incorporated with rRho-NM (EC-rRho-NM). More impressively, rRho-NM remained stable in expressing Nirs and AMO genes, increased nitrification and denitrification rate, and improved MBR effluent quality in the treatment of NFC. In conclusion, this work provides new insights into the application of advanced oxidation processes incorporated with bioaugmentation using rRho-NM for the treatment of NFC of old landfill leachate.