Study On Treatment Of Ammonia Nitrogen Wastewater By Membrane Aerated Biofilm Reactor(MABR)

The increasing emission of ammonia nitrogen wastewater aggravates the eutrophication of water bodies and seriously damages the ecological environment of water bodies.Economical and efficient removal of ammonia nitrogen from wastewater is now one of the key problems for the treatment of ammonia nitrogen wastewater.As a new type of wastewater treatment technology,membrane aeration bioreactor(MABR)has the advantages of non-foam aeration,biofilm stratification,simultaneous nitrification and denitrification,and can be applied to treat ammonia nitrogen wastewater for improved efficiency and reduced energy consumption.However,the membrane and technology of MABR for treatment of ammonia nitrogen wastewater still need to be optimized.In this thesis,two types of MABR reactors of MABR-PVDF and MABR-PTFE were firstly constructed through using PVDF hydrophilic and PTFE hydrophobic hollow fiber membrane modules.Their denitrification and decarbonization performance were investigated and compared under the hydraulic retention time of 24 h and sequential batch model by varying operation parameters.The two reactors were compared in terms of oxygen mass transfer characteristics,wastewater treatment effects,taxonomic analysis of microorganisms in biofilms,Alpha diversity,species and community composition to explore the feasibility,advantages and disadvantages of MABR-PVDF reactor.Finally,the superiority of MABR in treating ammonia nitrogen wastewater was explored through a comparison with the traditional anaerobic ammoniation method.Both MABR-PVDF and MABR-PTFE reactors could achieve efficient removals of nitrogen and carbon.The removals of COD,ammonia nitrogen and total nitrogen of MABR-PVDF reactor were 95.4%,79.6%and 71.8%,respectively,under its optimal operating parameters of aeration pressure=0.06 MPa,pH=8,peristaltic pump speed=60 r/min and C/N=5.The removals of COD,ammonia nitrogen and total nitrogen of MABR-PTFE reactor were 97.1%,80.0%and 69.6%,respectively,under its optimal operating parameters of gas flow rate=0.15L/min,pH=8,peristaltic pump speed=60 r/min and C/N=5.The effect of flow rate on biofilm shedding was less than that of flow rate on substrate diffusion.C/N ratio was the key parameter for implements of nitrification and denitrification.The comparative study showed that the oxygen mass transfer resistance of PVDF hydrophilic membrane was larger than that of PTFE hydrophobic membrane,and the mass transfer resistance was mainly resulted from porous membrane,liquid membrane and dense skin layer.MABR-PTFE reactor was more suitable for treating high COD wastewater,showing fast degradation rates of ammonia nitrogen and total nitrogen.The microbial richness and diversity of PTFE biofilms were superior to PVDF biofilms.The species composition of two biofilms was similar,and the shared species accounted for 59.3%of total species.The dominant flora in PVDF and PTFE biofilms mainly included Proteobacteria and Patescibacteria.Hydrophilic membrane PVDF could be applied to the MABR process.Compared with the ANAMMOX reactor,the MABR-PTFE reactor had a similar COD removal under an influent C/N of 3 or 5,and better removal efficiency of ammonia nitrogen and total nitrogen.The ANAMMOX showed a better ammonia nitrogen treatment efficiency when the C/N was 8.The main microbial flora of ANAMMOX activated sludge included Firmicutes and Bacteroidetes,which contain Bacilli,Chlorobia,Clostridia,and Anaerolineae,MABR process possesses the advantages of high microbial richness and diversified microbial species compared with ANAMMOX method,and is suitable for treating ammonia nitrogen wastewater.