Influence of Electric Current on Coupling 3-dimensional Biofilm-electrode With Sulfur Autotrophic Denitrification

To strengthen the removal of TN for wastewater treatment plant(WWTP) effluent,the performance and bacterial community of a coupling 3-dimensional biofilm-electrode with sulfur autotrophic denitrification technology(3DBER-S) were investigated at different electric current conditions.The operating result indicates that there are no significant impacts of electric current on denitrification performance in 3DBER-S.When electric current increases from 60 to 800 mA at a HRT of 12 h in3DBER-S,the proportion of hydrogen autotrophic denitrification process increases from 22.8%to74.4%.An average NO₃^--N and TN removal rate of 87%and 76%respectively is obtained at ρ(COD)/ρ(TN)(ρ(C)/ρ(N)) ratio of 1 and NO₃^--N concentration of 35 mg/L as well as pH =7.0-7.5 in the influent.The nirS gene clone library suggests that the bacteria similar to heterotrophic,hydrogen or sulfur autotrophic denitrifying bacteria occupy a certain proportion respectively in 3DBER-S,and the proportion of the bacteria similar to hydrogen autotrophic denitrifying bacteria increases with electric current increasing.It illustrates that there is a composite among heterotrophic,hydrogen and sulfur autotrophic denitrification process leading to a stable and high-performance nitrogen removal in 3DBER-S,and the increase of electric current contributes to hydrogen autotrophic denitrification.