Effects Of Hydraulic Characteristics On Microbial Community Characteristics In Biological Aerated Filter

Activated Sludge is widely used at home and abroad as traditional biological wastewater treatment.However,the amount of excess sludge is more and difficult to be treated in produced process of activated sludge,which has become a major problem.Biological aerated filter(BAF)is one of representative processes in the third generation biofilm method,has a high remove efficiency to SS and organic compounds,and can remove nitrogen and phosphorus.There is no sludge expansion in BAF.Therefore,BAF have a good application prospect in wastewater treatment.The paper takes upflow biological aerated filter as research object,studies on the hydraulic characteristics of flow field in BAF by application of CFD technology,analyze the impact of different of gas-water ratio for the hydraulic characteristics of flow field.In order to analyze the treatment efficiency of pollutants,it compares the effects of different hydraulic retention times(HRT)and gas-water ratio on removal contaminants,studies the removal effect of contaminants at along the way in BAF.In order to optimize the efficiency of sewage treatment,it analyzes the microbial community characteristics of BAF by Three-dimensional fluorescence spectroscopy(EEM),Scanning Electron Microscopy(SEM)and Macro genome technology.The study draws the following conclusions.(1)The paper compares the distribution of velocity field and turbulent kinetic energy at the different of gas-water ratio,and found that the hydraulic characteristics of the flow field are beneficial to improve the treatment efficiency of the wastewater in gas-water ratio of 5:1(2)The process of BAF has a better effect on contaminants.The results showed that the removal efficiency of COD,TN and NH4+-N was logarithmic at along the way in BAF.The removal effect of COD and TN mainly concentrated in the 0-25cm filter layer.The study found when hydraulic retention time is 5h,and gas-water ratio is 5:1,the removal efficiencies of COD,TN,NH4+-N,TP was higher and 92.0%,51.8%,48.2%,and 40.3%,respectively.(3)The distribution of extracellular polymeric substances(EPS)in microbes is different at different gas-water ratio and filter layer.With the increase of gas-water ratio,the content of compact EPS(TB-EPS)increased gradually,and the contents of soluble EPS(SMP)and loose EPS(LB-EPS)decreased gradually.The content of TB-EPS remained constant along the direction of filter layer,while the content of SMP and LB-EPS decreased first and then increased.Dissolved microbial byproducts and humic acids are common in EPS.(4)By the technology of SEM and macro genome,the dominant microflora in BAF system was Proteobacteria,and The abundance of microbial is higher for nitrogen and phosphorus removal,such as Comamonadaceae,Nitrospira,Hyphomicrobium,Nitrosomonadales,Planctomycetes,Bacillus,Zoogloea,Rhodocyclaceae,and so on.Microbial community structure is different at different gas-water ratio and filter layer.When gas-water ratio is 5:1,the abundance and diversity of denitrification type microorganism are higher than the other conditions.For different filter layer,10cm filter layer is higher the abundance of microbial than others.And the different of Microbial are more significant at along the way in BAF.(5)The hydraulic characteristics of the flow field affect the wastewater treatment efficiency by affecting the growth and metabolism of microorganisms.Comprehensive microbiological characteristics and results of wastewater treatment efficiency found that the flow field distribution in the system is beneficial to improve the efficiency of wastewater treatment,when gas-water ratio is 5:1.