Highly effective treatment of petrochemical wastewater by a super-sized industrial scale plant with expanded granular sludge bed bioreactor and aerobic activated sludge

One industrial scale plant has been constructed for annual treatment of 657,000 m(3) real petrochemical wastewater of 4649 +/- 651 mg/l COD and more than 50 mg/l petrochemicals. The plant system is divided into four parts, and the treatment process mainly functions in a 2200 m(3) anaerobic expanded granular sludge bed (EGSB) bioreactor and a 10,000 m(3) aerobic activated sludge (AS) bioreactor with the hydraulic retention time (HRT) of 62.8 h and 133.3 h, respectively. The plant has been successfully operated for more than 450 days, and the overall COD and petrochemical removal efficiencies of the plant are 85.6 +/- 2.5% and 81.5 +/- 4.8%, respectively. The removal efficiency of the aerobic AS bioreactor was higher than that of the anaerobic EGSB bioreactor, and most COD and petrochemicals were removed in the aerobic AS bioreactor. Further microbial diversity analysis revealed that the dominant microbes in the EGSB and AS bioreactors were assigned to Proteobacteria and Firmicutes and 4 dominant OTUs related with COD or petrochemicals removal were enriched in the bioreactors, showing that the microbial communities had been adapted to the petrochemical wastewater treatment. Based on the results, the newly built industrial plant exhibited good performance in petrochemical wastewater treatment and enriched microbes towards petrochemical wastewater treatment during operation. This strategy also has potential applications for other industrial wastewater treatment in the future.