| In recent years,nitrogen pollutants have gradually become the main water pollutants,efficient removal of nitrogen from water has turned to be a necessary trend.In order to improve the removal rate of nitrogen,Microbial Fuel Cell（MFC）,as a new clean and green technology,has become the focus of researchers.Many scholars adopt single point watering to combine MFC with traditional A~2/O（anaerobic-anoxic-aerobic）sewage treatment process to achieve simultaneous denitrification and power generation.However,due to the fast degradation rate and high removal rate of organic matter in anode chamber（anaerobic section）,the carbon source in cathode chamber（anoxic section）is insufficient,which hinders the denitrification process.While the rate of electrode autotrophic denitrification is relatively slow,so the removal efficiency of nitrate nitrogen in the whole system is low.Therefore,this paper attempts to set up a water inlet point in the cathode chamber（anoxic section）and build a step-feed MFC coupling A~2/O system.The process of enhanced heterotrophic denitrification of influent organics is studied to improve the removal rate of nitrate nitrogen in the coupled A~2/O system of MFC.And the effects of external resistance combination,influent distribution ratio and internal reflux ratio on the denitrification and power generation performance of the system are investigated.By optimizing the operation conditions of the system and analyzing the effectiveness of the system in the treatment of actual domestic sewage,the following conclusions are obtained:1.The system starts from continuous water inflow.After 30 days of culturing,when the external resistance on both sides is 200Ω,the output voltage of UA-A and UA-O were150±8 m V and 210±9 m V respectively,the removal rate of COD was 92.16%,the removal rate of ammonia nitrogen,nitrate nitrogen and total nitrogen were 50.97%,37.40%and 18.27%respectively.2.Adding microorganism packing in the aerobic chamber can effectively improve the removal rate of ammonia nitrogen in the system.Adjust the resistance combination on both sides of the battery and when the resistance combination（RA-A/RA-O）is 100Ω/900Ω,the total nitrogen removal rate of the system was increased to 64.41%,and the nitrate nitrogen concentration of the effluent was reduced to 7.99±1.02 mg·L-1.By adjusting the influent C/N,it was found that the removal effect of the system for high concentration ammonia nitrogen is poor,which still needs to be improved.3.It optimizes the deficiency of poor removal effect of nitrate nitrogen in the original system after adding the water inlet point of anoxic chamber to realize the subsection water inlet.By adjusting the ratio of influent and water distribution（Qvana:Qvano）of anaerobic chamber and anoxic chamber,it was found that the higher the influent flow rate of anoxic chamber was,the better the removal effect of nitrate nitrogen was.When the ratio of influent and water distribution was 1:3,the effluent concentration of nitrate nitrogen was only 2.93±0.96 mg·L-1.When the optimal ratio of water in the system was1:1,the total nitrogen removal rate could be increased to 79.94%.By adjusting the internal reflux ratio,it was found that the denitrification effect of the system increases first and then decreases with the increase of the internal reflux ratio.When the internal reflux ratio was 300%,the system reached the optimal operation state.4.In order to verify the practical application value of double cathode MFC of segmented influent,the operation parameters were as follows for the treatment of actual domestic sewage:the influent distribution ratio was 1:1,and the internal reflux ratio was 300%.The results show that the removal rate of COD and TN was 80.62%and 68.17%respectively,which were slightly lower than that of simulated wastewater.The research results have reference value for the practical application of step-feed double cathode MFC coupling A~2/O system.There are 35 pictures,12 tables and 80 references. |
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