Study On Three Demension Biofilm Electrode Reactor For Removal Of Nitrate Nitrogen From Slightly Polluted Groundwater

Three-dimensional biofilm electrode reactor?3D-BER?is a new type of water treatment technology.Different reactor structures and operating parameters can be used to remove different target pollutants and obtain different removal effects.Based on the analysis of the data and the preliminary research of the research group,this study constructed two new reactor structures.A reactor was flat plate three-dimensional biofilm electrode reactor,and the other was circular ring three-dimensional biofilm electrode reactor.Flat plate reactor adopted the structure of variable electrode spacing.The anode was graphite plate,the cathode was stainless steel plate,which arranged in parallel and filled with activated carbon as the granular electrode.Circular ring reactor adopted graphite rod and cathode as stainless steel mesh tube as anode,and filled with activated carbon as granular electrode.First of all,under the condition of no biofilm inoculation,the removal efficiency and influencing factors of nitrate nitrogen in water of two kinds of reactors under the action of pure electrochemistry were studied.Then,inoculate autohydrogenotrophic bacteria,to initiate two kinds of three-dimensional biofilm electrode reactors.The removal efficiency and influencing factors of nitrate nitrogen and trace organic compounds on two kinds of reactors were researched after initiation.The optimum operation conditions of two reactors were obtained by orthogonal experiment.Analysing the mechanism of three-dimensional biofilm electrode reactors by means of comparing difference treatment effect of pure electrochemistry and 3D-BER,and two kinds of three-dimensional biofilm electrode reactors.The main conclusions as follows:?1?Flat plate three-dimensional biofilm electrode reactor had a certain removal effect of nitrate nitrogen under the condition of pure electrochemical action,but the removal rate was low.The best removal rate of nitrate nitrogen was 60.32%when electrode distance was 50mm,current intensity was 80mA,influent nitrate concentration was 30mg/L,influent pH was 7,and HRT was 12h.?2?The influence of current intensity on flat plate and circular ring three-dimensional biofilm electrode reactors were similar,and they were in accordance with the three-stage theory proposed by Y.Sa KaKibara.With the increase of nitrate concentration,the removal rate of nitrate nitrogen increased first and then decreased.HRT was positively correlated with nitrate nitrogen removal rate and effluent ammonia nitrogen concentration,and negatively correlated with nitrite nitrogen accumulation.?3?The effect of influent pH was different on flat plate and circular ring three-dimensional biofilm electrode reactors.As influent pH risedfrom 6 to 9,the removal rate of nitrate nitrogen in flat plate reactor increased first and then decreased.However,nitrate nitrogen removal rate of circular ring reactor continued to rise.?4?Compared with flat plate and circular rings of three-dimensional biofilm electrode reactors under the same operating condition,The flat plate reactor was better than circular ring in most working conditions.The results showed that flat plate reactor has more uniform electric field,the distribution of reducing hydrogen was more uniform,and it can be used more efficiently by microorganism.?5?Three-dimensional biofilm electrode reactor had a certain removal effect of trace organic compound.The removal rate of COD_Mn was only 58.52%after 15h because autohydrogenotrophic bacteria were not dominant in the reactor.?6?When current intensity was 40mA,influent nitrate nitrogen concentration was30mg/L,influent pH was 7,and HRT was 14h,flat plate three-dimensional biofilm electrode reactor was under the optimum conditions to remove nitrate nitrogen.The degree of impact from high to low was current intensity,influent nitrate nitrogen concentration,influent pH and HRT.The optimum condition for the removal of trace organic compounds was current intensity was 40mA,influent nitrate nitrogen concentration was 10mg/L,influent pH was 7,and HRT was 12h.The degree of impact from high to low was influent nitrate nitrogen concentration,current intensity,influent pH and HRT.?7?When current intensity was 40mA,influent nitrate nitrogen concentration was10mg/L,influent pH was 9,and HRT was 10h,circular ring three-dimensional biofilm electrode reactor was under the optimum condition to remove nitrate nitrogen.The degree of impact from high to low was current intensity,influent pH,influent nitrate nitrogen concentration and HRT.The optimum condition for the removal of trace organic matter was current intensity was 40mA,influent nitrate nitrogen concentration was 10mg/L,influent pH was 7,and HRT was 12h.The degree of impact from high to low was influent pH,current intensity,influent nitrate nitrogen concentration and HRT.