Experimental Study On The Removal Of Nitrate From Lightly Contaminated Groundwater Using A Magnetic Bio-film Electrode Reactor (MBER)

In the bio-film electrode reactor,the formation of a good bio-film on the electrode is the key to the removal of organism and nitrate in the reactor.The electrode serves as the core of the reactor and supports the growth of microorganisms and plays a crucial role on the electrode wastewater treatment in the bio-film reactor.According to the principles and characteristics of the bio-film electrode treatment,the electrode is an important control factor for wastewater treatment.The performance of the electrode will directly affect the activity of the bio-film on the surface of the electrode and the internal Structure,thus affecting the wastewater treatment efficiency.Therefore,to find a good electrode to increase the biological affinity of the electrode to increase the amount of bio-film on the surface of the electrode is the key.In this experiment,the foamed nickel electrode was modified with nano-tetra-iron tetraoxide,and the magnetized modified nickel foam electrode was applied to the bio-film electrode reactor to study the effect of the electrode after the magnetization modification on the bio-film of the electrode surface and the electrode organism.Effect of bio-film reactor on removal performance of NO₃^--N and Organics in Contaminated Groundwater.The results showed that the specific gravity of the bio-film electrode and the electrode in the reactor subjected to the magnetization-modified electrode was 0.5,whereas the specific gravity of the bio-film electrode and the electrode in the reactor without the magnetization-modified electrode was only 0.4.After the magnetization modified electrode was applied to the bio-film electrode reactor,the removal rate of NO₃^--N in the reactor was increased from 77.5%to90.15%,and the removal effect was improved by about 14%.There is also a certain increase in the removal of COD.Only the improvement effect is not obvious,only about 9%.In this experiment,the best process combination for the removal of contaminants in the magnetic bio-film electrode?MBER?reactor was explored by combining orthogonal experiments.Orthogonal experimental results show that HRT has the greatest impact on MBER,followed by current,C/N,and finally temperature.HRT is 8h,the current is 80mA,C/N is 2 and the temperature is 32?.It is the best process combination for the treatment of contaminants by the magnetic bio-film electrode reactor?MBER?.In this experiment,by analyzing the effect of the operating parameters on the treatment of contaminated groundwater by the magnetic bio-film electrode reactor?MBER?,some rules for the removal of contaminants?MBER?were obtained:HRT is not as long as possible..When HRT=8 h,MBER can achieve good removal of contaminants.Current has a significant role in the removal of NO₃^--N from the bio-film electrode reactor.When the current reached 80mA,the strongest promotion effect was that the removal rate of NO₃^--N reached 99.06%with MBER,and the removal rate of COD reached 87.75%.When C/N=2,MBER has the best removal effect of pollutants,the removal rate of NO₃^--N reaches 96.55%,and the removal rate of COD reaches 87%.At a temperature of 32?,MBER has the best removal of contaminants.This experiment analyzed the effect of temperature on the key enzyme?NAR/NIR?activity in the denitrification process and the effect of substrate?NO₃^--N/NO₂^--N?concentration on the speed of the enzyme?NAR/NIR?stimulation.The results showed that NAR had a higher activity at a temperature of 32 and NIR had a higher activity at a temperature of 35.Above the optimal activity temperature of the enzyme,the enzyme activity decreases,and higher temperatures may deactivate the enzyme.In a certain concentration range,the utilization rate of nitrate and nitrite is positively correlated with the corresponding substrate concentration.In this experiment,the biofilm performance and biofilm growth characteristics of the electrode surface on the stable running MBER were analyzed.The results showed that the extracellular polymer?EPS?of the biofilm on the electrode surface also increased,and the polysaccharide in the extracellular polymer?EPS?.The?PS?content was increased by 0.59times compared to the unmodified electrode,and the protein?PN?content was also increased by 0.66 times compared to the unmodified electrode.Dehydrogenase activity is also improved compared to unmodified electrodes.After the electrode is modified by magnetization,the rate of film deposition on the surface of the electrode is accelerated,the rate of biofilm renewal is also accelerated,and the microbial species on the surface of the electrode is more abundant.