Removal of azimsulfuron and zoxamide using a tapered variable diameter biological fluidized bed combined with electrochemistry: Mass fraction division, energy metabolism activity and carbon emissions

The performance of the combination system of tapered variable diameter biological fluidized bed (TVDBFB) with electrochemistry (EC) was evaluated for removing azimsulfuron and zoxamide under different temperatures and influent concentrations. Maximum removal efficiency of azimsulfuron and zoxamide could reach 94% and 98% under higher influent concentration (about 780 mg/L). As temperature decreased from 32 ℃ to 8 ℃, the mS_e increased from 48% to 56%, and the mS_o and mS_xv decreased from 30% to 22% and 27% to 24%, respectively. As the influent COD equivalent concentration of azimsulfuron and zoxamide enhanced from 260 mg/L to 780 mg/L, the K_d increased from 0.06 d^-1 to 0.23 d^-1. Temperature and influent concentration were main influencing factors of DHA, ATP and ETS. Increasing aeration in TVDBFB and HRT in EC under shock conditions could improve azimsulfuron and zoxamide removal efficiency, however, it was also accompanied by higher carbon emissions.