Experimental Study On The Treatment Of Decentralized Domestic Sewage By Electricity-biological Coupling Technology

With the continuous development of China's social economy,the urban and county sewage treatment rates have reached a high level,so increasing the urban and county sewage treatment rate is no longer the main direction of the sewage treatment industry.For the typical areas represented by the vast rural areas,far away from the urban centralized sewage pipe network,the distributed sewage generated cannot be effectively collected and treated.The discharged sewage will affect the surrounding water environment and endanger human health.Decentralized sewage treatment has become Issues to be dealt with urgently.This paper aims at the current situation and requirements of decentralized sewage treatment in Gansu Province,which is typically represented by rural areas.On the basis of the development of decentralized sewage treatment technology,electricity-biological coupling technology is introduced into decentralized sewage treatment to effectively improve the sewage treatment effect and the treatment efficiency will further alleviate the environmental and health threats caused by decentralized sewage and improve the regional ecological environment.By analyzing and summarizing domestic and international decentralized sewage treatment technologies,this experiment combines biological methods and electrochemical methods,mainly biological methods,supplemented by electrochemical methods,and adopts electricity-biological coupling technology to treat domestic sewage And the removal effect of NH₄⁺-N?COD?TN and TP is used as the evaluation index to explore the removal efficiency of pollutants by the electricity-biological coupling system.First,this experiment set up a small test electricity-biological coupled reactor to explore the removal effect of pollutants at different voltages,hydraulic retention time and pH,and screened out the key regulatory factors that affect the electric-biological coupled reactor.In the same period of the experiment,a common bioreactor of the control group was set.Secondly,the experimental group static device?powered?and the control group static device?no power?were set up,the kinetics of pollutant degradation was fitted and high-throughput sequencing of biofilm samples was performed.The relationship between the degradation rate of pollutants and microbial diversity was analyzed.Finally,the pilot scale test is carried out on site through the pre-order laboratory test.Existing research results were verified by pilot test.Through the research in this paper,the following conclusions are obtained:Under the conditions of this experiment,under the effect of applied voltage,different hydraulic retention time and different influent pH,the removal effect of NH₄⁺-N?COD?TN and TP all showed significant difference?P<0.05?.The removal effect of the reactor is better than ordinary bioreactors.?1?When the hydraulic retention time is 4h,the influent pH is about 7.0,and the dissolved oxygen is about 4.5mg/L,after applying different applied voltages,the removal effect of NH₄⁺-N,TN changes significantly.When the voltage is 2V,The removal effect of NH₄⁺-N and TN are the best,the average removal rate is 58.95%and 39.29%respectively;when the voltage is 6V,the removal effect of NH₄⁺-N and TN drops sharply,even lower than that of NH₄⁺-N and TN without applied voltage.After applying different applied voltages?2V,4V and 6V?,there was no significant difference in the removal effect of COD and TP,and the average removal rate was above 63%and 19%respectively,but they were better than the removal effect of COD and TP without applied voltage.?2?When the reaction conditions are applied voltage 2V,influent pH is around 7.0,and dissolved oxygen is around 4.5mg/L,the hydraulic retention time is extended from 2h to 6h,except TP,the removal effects of NH₄⁺-N,COD,TN in the two reactor showed an upward trend,and the average removal rate of the electricity-biological coupled reactor in 6h was the highest,being 95.17%,73.09%,and 49.91%respectively.?3?When the reaction conditions are applied voltage 2V,hydraulic retention time is 4h,and dissolved oxygen is about 4.5mg/L,The removal effect of NH₄⁺-N in the electricity-biological coupling reactor is the best when the pH of the influent is 7,and the average removal rate is 71.52%.The change of the pH of the influent water has no excessive effect on the removal effect of COD.The effect is the best when the pH is 7-8,and the average removal rate is 69.67?72.3%.The pH of the influent water has a significant effect on the denitrification effect of the reactor.When the pH is 7-8,the removal rate of TN is the best,and the average removal rate is 45.96?50.57%.The dephosphorization effect of the electricity-biological coupling reactor is better under neutral alkaline conditions with a pH of7-8,and the average removal rate is 18.51?20.15%.?4?The kinetic analysis shows that the ammonia nitrogen and COD trends of the degradation water in the experimental group and the control group are more in line with the first-order reaction kinetic equation,and the degradation rate of the experimental group is higher than that in the control group.Under this test condition,as the electrode spacing increased from 5cm,10cm to 15cm,the average removal rate of NH₄⁺-N decreased from96.44%to 83.43%,and the average removal rate of COD decreased from 81.15%to 74.60%.The change of the electrode plate spacing has more influence on the removal effect of NH₄⁺-N than COD.The degradation rate of NH₄⁺-N when the electrode spacing is 5cm is significantly higher than 10cm and 15cm.Compared with the degradation rate of NH₄⁺-N,the difference in the degradation rate of COD under different electrode plate spacing is small,and the degradation rate at 10cm and 15cm is basically the same.Similarly,the effect of different applied voltages?1V,2V,3V,and 4V?on the removal effect of NH₄⁺-N is greater than that of COD.The removal efficiency of NH₄⁺-N is the best when the voltage is 2V,the average removal rate is 91.73%.Under this test condition,the degradation rate of NH₄⁺-N is good when the voltage is 1?2V,and the degradation rate of COD under different voltages is not much different.?5?The kinetic analysis shows that the degradation of ammonia nitrogen and COD in the wastewater of the experimental group and the control group is more in line with the first-order reaction kinetic equation.In the biofilm samples near the cathode and anode of the test group device?applying a voltage of 2.0V?,the dominant bacterial populations at the genus level were 19 genera and 13 genera?relative abundance>1%?,and the dominant bacteria under the phylum level belong to 7 phylums?relative abundance>1%?;In the biofilm sample of the control device?without voltage applied?,the dominant bacteria group at the genera level was 9 genera?relative abundance>1%?,and the dominant bacteria group at the phylum level were all 6 genera?relative abundance>1%?.After acclimatization,the population richness was significantly improved,so the degradation rate of pollutants in the test group was better than that in the control group.?6?Through continuous monitoring of the inlet and outlet water quality of the reaction device in the pilot test field test for a certain period of time,the effect of the removal of pollutants under the pilot reaction conditions was analyzed.And it is verified that the removal effect of the reaction device on NH₄⁺-N,COD and TN under the optimal working conditions is consistent with the previous test.In addition,the effects of dissolved oxygen,temperature and reflux ratio on the removal effect of the reactor were analyzed.The experiment found that when the dissolved oxygen was controlled at 5?6 mg/L,the removal rates of NH₄⁺-N and COD in the?and?stages reached the maximum,but it was not conducive to the denitrification of the device;When the dissolved oxygen was controlled at 4?5 mg/L,the removal rates of TN in the?and?stages reached the maximum,which were 43.38%and49.34%respectively.When the temperature is about 25?,the removal rates of COD,NH₄⁺-N and TN can reach 75.34%,93.42%and 47.93%respectively.With the temperature drop,the removal effect of NH₄⁺-N and TN is significantly lower than that of COD.The effluent COD,NH₄⁺-N and TN have the best removal effect at reflux ratios of 100?150%,100?150%and100%,and the removal rates can reach 82.09%,99.34% and 66.64% respectively.