Study On The Nitrogen Removal Efficiency And Membrane Fouling Performance Of Sidestream Anaerobic Ammonia Oxidation Membrane Bioreactor

Membrane bioreactor has the advantage of using membrane module to retain almost all biomass in the reactor,which can greatly shorten the start-up time of anammox.However,membrane fouling restricts the industrial application and development of membrane bioreactors.Therefore,this article takes the sidestream Anaerobic Ammonia Oxidation Membrane Bioreactor(Amx SMBR)as the research object,studies the start-up of the Amx SMBR,investigates the Nitrogen Removal efficiency of the Amx SMBR,changes in sludge properties of the Amx SMBR during the start-up process,critical flux,sludge and filter cake layer analysis,nitrogen balance and changes in microbial community structure.Secondly,the operating conditions of Amx SMBR are optimized,including the specific gas demand per membrane area and upstream sludge rate on membrane fouling rate.Finally,the effects of Amx SMBR’s nitrogen removal efficiency,membrane fouling rate,sludge and filter cake layer extracellular polymeric substances in the reactor,activity of anammox sludge and microbial community structure under temperature stress were studied.The main conclusions are as follows:(1)After the start-up of Amx SMBR,the influent concentrations of ammonia nitrogen and nitrite nitrogen were continuously increased from 50 mg/L to 450 mg/L in three stages.After58 days,The removal rates of NH4~+-N,NO2~--N and total nitrogen reached 90%,97%and 86%.In addition,the ratios ofΔNH4~+-N:ΔNO2~--N:ΔNO3~--N remained stable of 1:1:0.18.The critical flux of Amx SMBR was determined to be 8.63 LMH.Tightly bound extracellular polymeric substances were key factors to membrane fouling.Protein content is 2.42 g/m~2,polysaccharide content is 0.84 g/m~2.During the operation,the form changed from red comprehensive color granular sludge to planktonic sludge,which is one of the most significant characteristics of Amx SMBR.The dominant microbial species of Amx SMBR were Bacteroidetes,Planctomycetes,Proteobacteria.The abundances of them were 47.83%,21.2%,18.85%.The dominant anammox functional bacteria is Candidatus Kuenenia.The abundances of Candidatus Kuenenia was 17.08%.(2)In the optimization of the operating conditions of Amx SMBR,the best specific gas demand per membrane area is 0.36 m~3/(m~2·h),and the best upstream sludge rate is 2.3 mm/s.When the specific gas demand per membrane area is 0.36 m~3/(m~2·h)and the upstream sludge rate is 2.3 mm/s,the critical flux is 12 LMH and the membrane fouling rate can be effectively delayed.(3)In Amx SMBR under temperature stress,the removal rates of NH4~+-N,NO2~--N and total nitrogen reached 95%,95%and 86%with the temperature is 35°C and the influent NH4~+-N and NO2~--N concentration is 250 mg/L during the start-up of the Amx SMBR.When the temperature is 25°C,with the operation of Amx SMBR,the nitrogen removal efficiency of Amx SMBR becomes worse and worse,and the influent NH4~+-N and NO2~--N concentration were gradually decreases.The removal rates of NH4~+-N,NO2~--N and total nitrogen is also decreasing,and the reactor is on the verge of collapse.After the temperature rises to 35°C,the nitrogen removal efficiency of the reactor quickly returns to the state when the temperature is 35°C.It is suggested that Amx SMBR is more susceptible to temperature interference,which may be related to the existence of anammox bacteria in the form of plankton.(4)In Amx SMBR under temperature stress,when the temperature is reduced to 25°C,the membrane fouling rate will increase,but after the temperature is restored to 35°C,the membrane fouling rate will become the same as the original.In addition,a decrease in temperature will lead to a decrease in the relative abundance of the phylum Planctomycetes to which anammox bacteria belong.When the temperature rises,the abundance of the phylum Planctomycetes increases.When the temperature decrease,the total relative abundance of anammox bacteria decreases.And when the temperature rise,the total relative abundance of anammox bacteria rise.At 35°C,the anammox species had little change.When the temperature was reduced to 25°C,the relative abundance of Candidatus Brocadia decreased significantly,while the relative abundance of Candidatus Kuenenia and Candidatus Jettenia were not affected by the temperature.After the temperature rose to 35°C,the relative abundance of Candidatus Jettenia decreased significantly.And the relative abundance of Candidatus Jettenia increased rapidly and became the dominant genus of anammox.The relative abundance of Candidatus Kuenenia and Candidatus Brocadia changed little,indicating that Candidatus Jettenia was more resistant to temperature shock.