Intensification and microbial pathways of simultaneous nitrification–denitrification in a sequencing batch biofilm reactor for seawater‐based saline wastewater treatment

Abstract

AbstractBACKGROUNDThe optimum condition and potential mechanism of simultaneous nitrification–denitrification (SND) in a sequencing batch biofilm reactor (SBBR) have not been fully classified under salinity stress using real coastal seawater. In this study, a SBBR system under salinity stress was operated to optimize SND performance by changing the intermittent aeration intensity and drainage ratio (DR), and the microbial pathway of optimum SND was examined.RESULTSResults showed that the increase in salinity with coastal seawater ratio of no more than 50% obviously decreased SND efficiency from 66.4 ± 7.3% to 51.3 ± 7.4% mainly due to the decline of denitrification activity. The optimum SND performance of 68.1 ± 7.6% was observed when dissolve oxygen (DO) level decreased from 5.55 ± 0.31 mg L−1to 2.21 ± 0.42 mg L−1 in the aerobic phase of intermittent aeration and DR increased from 0.14 to 0.23. More functional bacteria including anoxic and aerobic denitrifiers coexisted under the optimum condition. Also, heterotrophic nitrifiers rather than autotrophic nitrifiers mainly contributed to nitrification under salinity stress in the optimum system.CONCLUSIONSA SBBR system showed efficient SND under salinity stress by control of DR and intermittent aeration intensity due to the enhancement of functional bacteria including anoxic and aerobic denitrifiers and heterotrophic nitrifiers. © 2018 Society of Chemical Industry