Construction And Performance Study Of MABR With Heterotrophic Nitrification-Aerobic Denitrification Function

High ammonia nitrogen wastewater due to its high concentration of ammonia nitrogen?200⁶000mg/L?and organic matter,strong biological toxicity,and difficult treatment,if it is directly discharged into the natural water without reasonable disposal,it will not only increases the operation cost of wastewater treatment,but also may result in the aggravation of eutrophication in environmental water.Heterotrophic Nitrification-Aerobic Denitrification?HN-AD?technology means that HN-AD bacteria can rapidly convert the nitrogenous substances such as ammonia-nitrogen?NH₄⁺-N?,nitrite nitrogen?NO₂^--N?and nitrate nitrogen?NO₃^--N?transformed into nitrogenous gas during the aerobic conditions,and there is basically no accumulation of harmful intermediate products in reaction process,including NO₃^--N and NO₂^--N.Meanwhile,HN-AD bacteria also have the characteristics of resistance to extreme environments?high ammonia nitrogen,high salt,low temperature?and high pollutant removal efficiency,which makes HN-AD technology become the focus of attention in the field of high ammonia nitrogen wastewater treatment.However,the existing biological nitrogen removal process is difficult to maintain stable aerobic conditions,which can easily affect the HN-AD bacteria enrichment and nitrogen removal activity in the system.Membrane aeration biotechnology has the characteristics of bubble-free aeration and high oxygen utilization?achieved 100%?.The hydrophobic hollow fiber membrane not only can be used as both a diffuser without bubble aeration but also as a carrier for biofilm growth.It has been applied in Membrane Aerated Biofilm Reactor?MABR?.Therefore,in order to investigate the effect of MABR on domestication and enrichment of HN-AD bacteria and its ability to treat high ammonia nitrogen wastewater,the following studies were conducted.Firstly,this paper compares the oxygenation performance of MABR with different oxygen supply forms under clear water conditions;Secondly,when the traditional MABR?open-ended and closed-end?under two oxygen supply modes and the aeration-cycle MABR were inoculated the HN-AD bacteria with high NH₄⁺-N tolerance and high denitrification efficiency were isolated and screened from the biogas slurry of pig plant in the early stage of the research group,then the performance of it for the treatment of high ammonia nitrogen simulated wastewater are compared and studied;the SEM technique was used to explore the changes in the apparent ecological structure of the biofilm during the above process,then dynamic analysis of high-throughput sequencing technology was used to analyze the microbial community structure and species diversity changes of traditional MABR and oxygen cycle MABR in the treatment of high ammonia nitrogen simulated wastewater,and the effects of the key bacteria with HN-AD function on the nitrogen removal performance of MABR system were studied from the microbial perspective;Finally,the removal of carbon and nitrogen performance of aeration-cycle MABR in the treatment of real high ammonia nitrogen wastewater was studied,and the feasibility of the oxygen cycle MABR with HN-AD function for real wastewater treatment was evaluate.The main results were showed:?1?The oxygen transfer performance of MABR with different oxygen supply modes under clear water condition showed that in different pressure conditions,the aeration-cycle MABR has the shortest time to accomplish the saturated DO;in addition,the K_Laa value was compared in the traditional and aeration-cycle MABRs,revealing that it the highest oxygen mass transfer rate from aeration-cycle MABR was achieved in the clear water condition,which was beneficial to the rapid formation of an aerobic zone in the outer layer of the biofilm.?2?The results of the nitrogen removal performance and the characteristics of bacterial diversity of the traditional MABR demonstrated that MABR with both open-ended and close-ended oxygen supply modes could rapidly achieve the biofilm formation,and the average removal efficiencies of NH₄⁺-N,TN and COD in open-ended MABR for high ammonium synthetic wastewater treatment were all greater than those in closed-ended one to show a better nitrogen and COD removal performance.The high-throughput sequencing analysis revealed that rapid enrichment of HN-AD bacteria was achieved during the biofilm formation,and high abundances of HN-AD bacteria?Acinetobacter 22.1%,Pseudomonas 43.2%?were kept during the stabilization of the open-ended MABR.But closed-ended MABR didn't achieve HN-AD bacteria enrichment.A higher DO condition provided by open-ended MABR promoted greater abundance of HN-AD bacteria enrichment than those of close-ended one to enhanced treating high ammonium wastewater.?3?The results of the nitrogen removal performance and the characteristics of bacterial diversity demonstrated that the average removal rates of NH₄⁺-N,TN and COD in aeration-cycle MABR were achieved 80.3%,76.7%and 82%,respectively,among which the average removal rates of NH₄⁺-N and TN were 21.16%and 19.9%higher than that of open-ended MABR.The high-throughput sequencing analysis revealed that the aeration-cycle MABR enriched HN-AD bacteria like Acinetobacter?53.54%?.The stable and high DO condition of the aeration-cycle MABR?3⁷mg/L?promoted the growth of HN-AD bacteria,which enhanced the nitrogen removal performance of the reactor.?4?In this experiment,the results of aeration-cycle MABR treatment of pig-plant wastewater showed that when the influent COD concentration was 1088²510mg/L,and the concentration of NH₄⁺-N was 517⁷85mg/L,the average removal rates of NH₄⁺-N,TN and COD in aeration-cycle MABR were achieved 38%,33%and 53%,respectively.It suggests that aeration-cycle MABR has potential treatment effect on actual high-strength ammonium-nitrogen wastewater.