Advanced treatment of tannery wastewater using the combination of UASB, SBR, electrochemical oxidation and BAF

BACKGROUND: Wastewater discharged fromtannery industries is highly complex, concentrated, and toxic. Inviewof the varying nature of discharged wastewater and the numerous small industries in China, there is a need for highly efficient treatment processes that are simple to operate and have low/reasonable construction and operating costs. RESULTS: An integrated process of upflow anaerobic sludge bed (UASB) -sequencing batch reactor (SBR)-electrochemical oxidation (EO)-biological aerated filter (BAF) was developed at lab scale for the treatment of tannerywastewater with an initial chemical oxygen demand (COD) of 8300-9250mgL(-1). The results show that, under the optimum conditions, the efficiency of removal of COD, total suspended solids, total nitrogen, ammonia, oil-grease, S2-, total Cr and Cr6+ was more than 90%, and the quality of the final effluent met the national discharge standard of China set for the leather tanning industry. The UASB process removed a considerable proportion of easily degradable organics and improved the biodegradability of thewastewater, while the SBR played an important role in the removal of nitrogen and residual COD. The EO process further enhanced the biodegradability of the SBR effluent, and finally, post-polish treatment was accomplished in the BAF. The ecotoxicity of the wastewater was remarkably reduced after undergoing the hybrid treatment. CONCLUSION: This work demonstrates that the hybrid system has the potential to be used for the advanced treatment of high-strength tannery wastewater. (C) 2016 Society of Chemical Industry