Research On Electrochemical Technology To Enhance The Use Of Marine Anaerobic Ammonia-oxidizing Bacteria To Treat High-salinity Nitrogen-containing Wastewate

To date,the application of traditional biological nitrogen removal technologies have been limited by high salinity in saline wastewater treatment because of the imbalance of osmotic pressure inside and outside microbial cells.Marine anammox bacteria（MAB）naturally have good salt tolerance,which could maintain excellent nitrogen removal performance in saline wastewater treatment.However,the application of MAB is still a challenge in saline wastewater treatment due to the low growth and high sensitivity.In this work,the nitrogen removal performance of MAB in saline wastewater treatment was investigated by combining bioelectrochemical technology.The main findings are as follows:（1）Exerting applied voltage promotes the nitrogen removal performance and bioactivity of MAB in saline wastewater treatment.The maximum total nitrogen removal rate（TNRR）of MAB reached 0.65 kg/（m³·d）at the optimal voltage of 1.5 V,which was 27.45%higher than that of control.Besides,electrical stimulation reduced microbial diversity of MAB-consortia,but the relative abundance of Candidatus Scalindua at the voltage of 1.5 V increased by 4.63%compared with that of control.Furthermore,the EPS and heme c contents at 1.5 V were increased by 51.98%and 40.00%compared with the control reactor,which implied that the MAB bioactivity was enhanced by the electrical stimulation.According to the kinetic analysis,the lag time of nitrogen removal process shortened by 0.72 h by the remodified Logistic model at the voltage of 1.5 V.However,the bioactivity of MAB was inhibited by higher voltage（>2.0 V）,the TNRR decreased to 0.33 kg/（m³·d）.Subsequently,the TNRR recovered to 0.61 kg/（m³·d）after voltage-cut,which indicated that the bioactivity of MAB was a recoverable process.（2）Ammonium removal was driven by single-chamber microbial electrolysis cell（MEC）for treating saline wastewater.In this work,NH₄⁺-N could be converted to N₂by the catalysis of MAB without the supply of exogenous NO₂^--N.When the applied voltage increased from 0.5 V to 1.1 V,the ammonium removal rate（ARR）was also enhanced.At the voltage of 1.1V,ammonium removal rate and total nitrogen removal rate（TNRR）reached the maximum of 55 and 50 g/（m³·d）,respectively.Meanwhile,ammonium anoxic removal was predominantly attributed to anodic anammox process with the contribution of 77.12-91.05%,a small amount of ammonium was removed by anodic nitrification coupled with anammox process.As the further increase of applied voltage,more NO₂^--N and NO₃^--N were accumulated in reactor,the TNRR continuously decreased to 34 g/（m³·d）at the voltage of 1.5V.Furthermore,ammonium anoxic removal only resulted from anodic nitrification coupled with anammox process at 1.5 V.Besides,compared with the microbial community structure of suspended sludge,MAB and electroactive nitrifying bacteria were enriched and strengthened on the anode biofilm.The anodic anammox and anodic nitrification coupled with anammox reaction processes were well driven by Candidatus Scalindua,Nitrosmonas and Nitrospira in this work,and the relative abundances at anode biofilm were19.27,0.84 and 0.21%,respectively,which further revealed the removal mechanism of ammonium in MEC.