Study On Enhanced Denitrification Of Municipal Wastewater By Improved Silicone Tube Membrane Aerated Bioreactor

Membrane aerated bioreactor,as a new and improved high-efficiency denitrification technology,adopts the oxygen supply mode of membrane aeration on the basis of the traditional biofilm method,and improves the O2 utilization rate reaching close to 100% by improving the mass transfer of oxygen to the biofilm,which is 5～7 times the utilization rate of O2 in traditional aeration,and can avoid secondary pollution caused by volatile substances entering the atmosphere with bubbles in the traditional aeration process.Biofilms with anisotropic mass transfer can help achieve simultaneous nitrification and denitrification.In this paper,the improved silicone tube membrane module was firstly studied on the start-up of membrane hanging,and the optimal membrane module form and the optimal membrane hanging conditions were determined.Then,on this basis,the influence of aeration pressure,HRT and temperature on the nitrogen and carbon removal effect of MABR was investigated.At the same time,high-throughput sequencing was carried out on the sludge retained at each stage of the experiment,to explore the dynamic changes of community structure,community diversity and species abundance under different operating parameters of MABR,and reveal the correlation between biofilm microecosystem and process operating conditions.The results show that:The best form of membrane module is the silicone tube wrapped with non-woven cloth,the membrane hanging effect is the best at 20 kPa and two-step start-up,the removal rate of 70% ammonia nitrogen can be reached on the 8th day,and the removal rates of ammonia nitrogen,TN and COD can reach 87%,80% and 70%respectively after raw water is added.When the reactor was started under the optimal conditions of membrane hanging,the maximum nitrogen and carbon removal efficiency of MABR was achieved when the aeration pressure was 20 kPa,HRT was12 h and the temperature was 30℃,the maximum removal rates of ammonia nitrogen,total nitrogen and COD were 90.97%,86.59% and 88.61%.Microbiological research showed that Proteobacteria,as the main functional bacteria group for nitrogen and carbon removal,gradually decreased its relative abundance with the gradual decrease of aeration pressure from 20 k Pa to 10 k Pa,and whether HRT increased from 12 h to14h or 12 h to 10 h,the proportion of Proteobacteria in the biofilm all showed a decreasing trend,and the proportion of Proteobacteria also decreased with the decrease of temperature.Therefore,the relative abundance of functional microflora of MABR was the highest when the aeration pressure was 20 k Pa,HRT was 12 h and the temperature was 30℃,the effect of nitrogen removal and carbon removal was the best,the top three bacteria groups were Proteobacteria,Chloroflexi and Actinobacteriota,accounting for 35.37%,22.62% and 15.12%,respectively.