Nitrate Removal From Simulative Groudwater By A Novel Three-dimensional Biofilm-electrode Reactor

In the recent years,nitrate pollution in groundwater was more and more increasing and has been paid more and more attention.The bio-electrochemical denitrifying technology combining electrochemical process and autotrophic biological denitrification is considered to be a new technology,which is more suitable for the treatment of nitrate pollution of groudwater compared with the heterotrophic denitrification process.Hence,the bio-electrochemical denitrifying technology has become an important issue domestic and broad.Researches showed that redox mediator could accelerate denitrification;while the accelerating bio-electrochemical denitrification by redox mediator has not been developed.Consequently,based on the commercial actived carbon and the anthraquinone-modified actived carbon,the effect of anthraquinone-modified actived carbon on three-dimensional biofilm-electrode reactor was investigated.The main conclusions were as follows:1)The result of start-up and running in the square cylinder reactor suggested that the optimum distance was 3cm,and the maximum removal rate of nitrate was 46%.The optimal operating conditions were:pH 9,110mL/h of flow rate and 30mA of current.When the pH was increased from 6 to 9,the removal rate of nitrate increased.The removal rate was 45%,the effective current was 14mA and the current efficiency was 49%.The denitrification rate was 0.09mg NO₃^--N/?d·cm²?when the pH was 9.The nitrate removal rate increased first and then decreased when the flow rate increased from 90mL/h to150mL/h.The optimal flow rate was 110mL/h and the nitrate removal rate was 43%.In this condition,the effective current was 14mA and the current efficiency was 46%.The denitrification rate was 0.09mg NO₃^--N/?d·cm²?.When the current ranged from 10 to40mA,the removal rate of nitrate increased first and then decreased,30mA was the optimal current.The removal rate was 46%and the current efficiency was 46%.2)The characterization result of three kinds of activated carbon showed that the prepared activated carbons had close-packed structure and multihole,which were beneficial to bacteria growth.There were more characteristic absorption peaks in the infrared spectra of the activated carbons with 1,5-dichloroanthraquinone.The surface functional groups of prepared control and 1,5-dichloroanthraquinone activated carbons increased by 22.1%and 86.5%than the commercial.The acidic surface functional group increased by 18%and 20%.The alkalescent surface functional groups were 1.5 and 5times of the commercial.Their surface areas,pore diameters and pore volumes had no greatly difference.3)The three noval three-dimensional biofilm-electrode reactors with commercial,control and 1,5-dichloroanthraquinone activated carbons were started-up and run.The effects of influent pH,flow rate and current on the denitrification characteristics of three reactors were investigated.The result revealed that the performance of the reactor including 1,5-dichloroanthraquinone activated carbons was the best when the cultivation was finished.The removal rates of nitrate were 2.5 times and 3 times of the rectors including commercial and the control activated carbons.The optimal operating conditions of the three reactors were 9 for pH,110mL/h for flow rate and 15mA for current.When the pH was 8,the removal rate of nitrate in the reactor including1,5-dichloroanthraquinone activated carbons reached 60%,which were 3 and 1.5 times of other two reactors.when the flow rate was 110mL/h,the removal rate of nitrate was 80%,which were 3.6 and 1.11 times of other two reactors.The removal rate of nitrate was 60%,which were 1.28 and 1.2 times of other two reactors when the current was 15mA.In conclusion,the denitrification characteristics of the novel three-dimensional biofilm-electrode reactor were carried out with the preparation of anthraquinone particle electrode in this study.The results will provide theory and technique basic for nitrate removal in groundwater.