Integration of methanogenesis with anaerobic ammonium oxidation and denitrification for treatment of tannery wastewater in an uasb reactor

This study attempted to integrate methanogenesis with simultaneous anaerobic ammonium oxidation (ANAMMOX) and denitrification by installing an external nitrate and nitrite reflux system in an upflow anaerobic sludge blanket (UASB) reactor for anaerobic treatment of tannery wastewater. During the whole 400-d operation period, the denitrification and ANAMMOX bacteria were cultured and enriched before granular sludge formed in the reactor to continuously remove nutrient. The removal efficiency of total nitrogen (TN), NH4+-N, NO2--N, and NO3--N were 71.6%, 44.1%, 98.4% and 83.7%, respectively. COD also showed high removal efficiency of 73.7-82.1% with an influent concentration of 3,760 mg L-1. Contributions of ANAMMOX, short-run denitrification, and complete denitrification to TN removal were approximately 38.3%, 16.4%, and 45.3%, respectively. This study also revealed that the ANAMMOX could coexist with methanogenesis in the UASB reactor. Moreover, the stability of the reactor could be affirmed after the sensibility of the reactor to the sudden changes was individually investigated with a series of fixed operation parameters. Therefore, this study demonstrated the potential application of the innovative promising UASB system in tannery wastewater treatment.