Study On A/O Semi-biofilm Nitrogen Removal Reactor Enhanced By Microbial Agents And Microbial Community Characteristics

Nitrogen pollution dominated by ammonia nitrogen has become a problem that must be faced by society.Traditional biological methods are affected by many factors in the process of nitrogen-containing wastewater treatment,which puts forward higher requirements for the treatment process.On the basis of maintaining the traditional biological treatment,there is an unsolved problem that how to further improve the treatment effect of nitrogen pollution by the process.In this paper,the traditional A/O activated sludge process was improved to combine the activated sludge process with the fixed biofilm process.Combined with the rapid development of microbial agent technology in recent years,the treatment effect of ammonia-nitrogen wastewater with low C/N was studied,as a reference for the future improvement of water treatment process.?1?Firstly,after a 35-day start-up period,a semi-biofilm A/O denitrification reactor was successfully formed and operated.The average removal rates of COD,NH₄⁺-N and TN in simulated wastewater were 52%,60%and 37%.In the start-up process,the biomass of the reactor is suitable,but the removal rate of pollutants is low.?2?Subsequently,it was found that short hydraulic retention time had a great impact on the removal efficiency of the three pollutants.Increased C/N ratio did not affect COD removal efficiency,but had a great impact on the removal rates of NH₄⁺-N and TN.Nitrite reflux ratio would affect TN removal.Increasing reflux ratio in an appropriate range would improve the removal efficiency of TN.Finally,the hydraulic retention time was determined to be 24 hours,the C/N ratio was 4,and the nitrate reflux ratio was 200%.Under these conditions,the removal rates of COD,NH₄⁺-N and TN were higher than 80%,80%and 60%respectively.?3?By adding ammonia nitrogen removal agent,it was found that the COD removal rate of the system did not change.The removal rate of NH₄⁺-N was higher than80%,and the system had impact resistance to NH₄⁺-N load of influent,while the removal rate of TN was not significantly improved.After adding denitrifying agent,there was no obvious change on the removal rates of COD and NH₄⁺-N according to the previous stage influent index.The removal rate of TN was affected by the concentration of organic matter.Appropriate increase of the concentration of organic matter in the influent was beneficial to the removal of TN.On the contrary,excessive increase of the concentration of organic matter in the influent would affect the quality of effluent water.After stabilization,the average removal rate of TN in the reactor system was over 67%.?4?The microbial community information in the reactor was obtained by High-throughput Sequencing,and the microbial community with strong function was obtained in the reactor.The relative abundance ratio of Preteobacteria and Bateroidetes in all samples was more than 70%.Preteobacteria contains microorganisms related to denitrification.Bateroidetes are mainly microorganisms that can degrade organic matter.At the same time,diversity analysis showed that the microbial diversity of different stages?before and after adding microbial agents?and different functional areas?anoxic and aerobic pools?of the reactor varied greatly.