Sustainable pollution removal and resources recovery from electroplating wastewater by coagulation, advanced...

Electroplating wastewater contains high concentrations of dissolved organic matter, heavy metal ions (HMs), refractory organic compounds (ROC), and the complicated composition of effluents. Bioaugmentation presents an efficient strategy for eliminating pollution and recycling resources from electroplating effluent. In this study, simultaneous removal of pollution and sustainable resources recovery from electroplating wastewater were conducted by polyferric sulfate (PFS)-based coagulation, ultraviolet (UV)-activated persulfate (PS) (UV-APS)-based advanced oxidation coupling with bioaugmentation. To reduce carbon emissions and achieve carbon neutrality, genetically engineered Vibrio natriegens with an aerobic sulfate reduction pathway (GeVin) was introduced to remove sulfate, organics, and HMs, which further promoted generation of metal sulfides. The results of coagulation by PFS eliminated 34.68% of chemical oxygen demand (COD), 38.56% of ammonia nitrogen (NH₄-N), 36.30% of ROC, and 16.67% of HMs. The rest of refractory contaminants in the effluent of coagulation were oxidatively degraded by UV-APS to improve biodegradability index. The bioaugmentation using immobilized GeVin (IMGevin) coupled with membrane bioreactor (MBR) (IMGevin-MBR) significantly removed 98.25% of COD, 96.23% of NH₄-N, 99.42% of biochemical oxygen demand (BOD), 97.85% of sulfate, and 97.68% of HMs. Mechanism analysis indicated that sulfate derived from PFS-based coagulation and UV-APS provided more electron acceptors to generate H₂S metabolized by GeVin, contributing to HMs removal via sulfate reduction pathway. Furthermore, IMGeVin-MBR decreased startup phase, hydraulic retention time (HRT), increased the microbial activity, functional microbial community and abundances of genes related to sulfate metabolism, resulting in improvement of systemic stability. Meanwhile, IMGeVin-MBR decreased the total treatment cost, sludge yields, and greenhouse gas (GHG) emissions for treatment of electroplating wastewater. In conclusion, this study provides a sustainable pollution removal and resources recovery strategy for treating electroplating wastewater.