Application Research Of Electrode Biofilm Reactor In Advanced Treatment Of Tail Water Of Sewage Plant

With the increasingly stringent sewage discharge standards in China,it is of great significance to carry out the research on the advanced treatment technology of tail water in wastewater treatment plant.The composition of pollutants in the tail water of sewage plant is complex,among which TN(NO₃^--N,NO₂^--N and NH₄⁺-N)is the most likely to cause eutrophication of water body.In addition,the C/N ratio of tail water from wastewater treatment plants in China is generally low,resulting in poor biological denitrification effect.Therefore,compared with other pollutants,nitrogen removal is more difficult.Deep nitrogen removal is the main goal of advanced treatment of tail water in wastewater treatment plant.In this thesis,two electrode biofilm reactors were constructed:heterotrophic coupled hydrogen autotrophic electrode biofilm reactor(3DBER)and heterotrophic coupled hydrogen and sulfur autotrophic electrode biofilm reactor(3DBER-S).Gradient current was used to start the reactor,and then the effects of current intensity,C/N,HRT and temperature on the deep denitrification of the reactor were investigated.Microbial community diversity and community structure were analyzed by high-throughput sequencing.The main conclusions were are follows:Gradient current was used to start 3DBER and 3DBER-S.After 36 days of operation,the TN removal rate of 3DBER and 3DBER-S was more than 90%,and the NO₃^--N removal rate was more than 95%,indicating that the startup was successfully completed.When the current intensity of 3DBER was 5 m A,the accumulation of NO₂^--N in the effluent was the highest,reaching 4.37 mg/L.NO₂^--N accumulation decreased with the increase of current intensity until the acclimation was completed below 0.5mg/L The concentration of NO₂^--N in 3DBER-S effluent was less than 2 mg/L.NH₄⁺-N accumulation in effluent of 3DBER-S was higher than that of 3DBER.With the increase of current intensity,the effluent p H of 3DBER and 3DBER-S decreased gradually.The denitrification effects of 3DBER and 3DBER-S under different current intensities,C/N,HRT and temperature were further studied.As the current intensity increased from 60 m A to 180 m A,the TN removal rate of 3DBER increased.When the current intensity continued to increase to 240 m A,the TN removal rate was not significantly different from that at 180 m A,which was stable at about 65%.When the current intensity continued to increase,the TN removal rate began to decrease.However,the current intensity had little effect on the nitrogen removal efficiency of 3DBER-S.The current intensity of hydrogen inhibition effect in 3DBER-S was 400 m A,which was higher than that in 3DBER.Under the same current intensity,the accumulation of NO₂^--N in the effluent of 3DBER-S was less than that of 3DBER,which was lower than1 mg/L,the concentration of NH₄⁺-N was higher than that of 3DBER.With the increase of current intensity,the effluent p H values of the two reactors decreased.The p H value of effluent from 3DBER-S was always lower than that of 3DBER from 7.0 to 7.5.Under the same C/N condition,the TN and NO₃^--N removal rates of 3DBER-S were good,especially under low C/N condition.The NO₂^--N accumulation of 3DBER-S was always less than 3DBER,below 1 mg/L.The effluent p H of both reactors increased with the increase of C/N,and 3DBER-S had better p H stability than 3DBER.Under the same HRT conditions,3DBER-S not only had high nitrogen removal efficiency,but also had certain advantages in controlling NO₂^--N accumulation.The effect of temperature on the reactor was obvious.At 10?15°C,the denitrification effect of3DBER-S decreased significantly and the accumulation of NO₂^--N increased.The results of high-throughput sequencing analysis showed that the detection rates of Dechloromonas,Comamonadaceae and Accumulibacter in 3DBER were 32.61%,14.68%and 4.24%,respectively.Proteobacteria accounted for the largest proportion in3DBER-S,accounting for 64.87%.At the genus level,Thauera with denitrification function had a large microbial composition,accounting for 3.2%and 13.7%in fillers and cathodes,respectively.In addition,3DBER-S also contained denitrifying bacteria of Sulfurimonas and Acidovorax with S and H₂ as electron donors,respectively.