A Novel Composite Membrane Aerated Biofilm And Its Nitrogen Removal Performance Research

Water is one of the resources that human beings live on the earth.But with the rapid development of industrial technology,environmental problems become increasingly important.The discharge of nitrogen-containing pollutants causes serious pollution to water bodies,which not only leads to eutrophication of water bodies,lake bloom and Marine red tide,death of fish due to hypoxia,destruction of Marine ecological chain,but also endangers human health.In this paper,a new technology combining immobilization technology with membrane aerated biofilm reactor is studied,aiming to create a new type of biological nitrogen removal reactor with short start-up time,small footprint,controllable microbial concentration and low energy consumption.At the same time,the anammox bacteria were enriched in a mixed bioreactor,and the anammox effects of different forms of AnAOB bacteria were investigated,which laid a theoretical foundation for future studies on inorganic autotrophic nitrogen removal.Synthesis of composite membrane aerated biofilm(CMAB)by coating PVDF membrane with gel can shorten the startup time.The mechanical strength of the thicker gel film was higher,and the mass transfer coefficient of the thinner gel film was higher.Meanwhile,the 0.5mm thick gel film crosslinked by NaNO3 was the best gel film for substrate mass transfer,indicating that the mass transfer effect was related to the thickness of the film and the choice of crosslinking agent.The short-range nitrification of CMAB was studied,and most NH4+-N was transformed into NO2--N in the cross-linked gel membrane of NaNO3.However,H3BO3 cross-linked gel film is not suitable for short-range nitrification,especially the 1mm thick film of H3BO3 cross-linked does not produce obvious NO2--N.The simultaneous nitrification and denitrification(SND)effects of membrane aerated biofilm(MAB)and two CMAB(0.1mm and 1mm)using NaNO3 crosslinking were compared.Most NH4+-N can be removed by SND process.Due to the use of microbial immobilization technology,CMAB has the advantage of fast start-up time,and the thickness and biomass of the biofilm can be controlled by adjusting the amount of gel.The COD removal rate of thin CMAB was the highest,about 88%,while that of thick CMAB was the second highest,and that of MAB was the lowest.The flat film limits the air pressure below 3kPa,greatly reducing the aeration cost.For 0.1mm biofilm,1kPa air pressure can make it reach the maximum TIN removal rate.A 72-day experiment was conducted in an anaerobic hybrid bioreactor to evaluate the effect of NH4+load and organic matter load on the system treatment.The anammox efficiency of the mixed bioreactor remains as high as 80%for long term synthetic wastewater regardless of the organic load.When COD/N=0.04 and 0.16,organics had little effect on autotrophic nitrogen removal system and did not change its effect on nitrogen utilization.Among the three forms of AnAOB,suspended sludge showed the highest anammox capacity,followed by biofilm.Due to the expansion of gel pellets floating on the water surface,the suspended sludge embedded in the gel has nitrification effect.Based on this phenomenon,NaHCO3 and Al2(SO4)3-treated gel balls were used to develop the gel pellet pore-making technology,so that it has relatively uniform internal pores.The pore-making technology can generate more channels in the gel pellet for gas dispersion.