Study On Fast Start-up Of Anammox Biofilm Reactor Based On Microbial Quorum Sensing

As a new wastewater biological nitrogen removal process,the anaerobic ammonium oxidation?ANAMMOX?process has the advantages of economic and efficiency,and has attracted the attention of environmental protection workers at home and abroad.However,anaerobic ammonia-oxidizing bacteria have very low cell yields,long doubling times,and stringent metabolic conditions which lead to slow start-up of the anammox reactor.In view of this,based on the theory of microbial quorum sensing,the rapid enrichment of anammox bacteria can be achieved by increasing the concentration of AI-2 activating factor?boron?in the influent to solve the problem of long startup time of anammox reactor.At the same time,a method for the determination of the concentration of trace microbial signal molecules AI-2 in actual water samples was established.Then,polyvinyl alcohol?PVA?hydrogel was prepared by chemical crosslinking of boric acid,and the Anammox SBBR reactor was started quickly by using PVA gel beads as a biocarrier.Finally,the microbial community structure in the SBBR reactor was analyzed by high-throughput sequencing to provide theoretical basis and technical support for the rapid start-up of anaerobic ammonia oxidation SBBR process.The main results are as follows:?1?A pre-column derivatization-solid phase extraction-high performance liquid chromatography tandem fluorescence detection method was developed for the detection of trace microbial signal molecules AI-2 in actual water samples.This method has the advantages of low detection limit,accuracy and precision.The method was used to detect the concentration of signal molecule AI-2 in different forms of Anammox sludge.The results showed that signal molecule AI-2 was widely found in Anammox sludge.?2?The anaerobic ammonium oxidizing bacteria were enriched using the SBR mode of operation using common activated sludge as inoculum.By increasing the boric acid concentration in the influent water,the reactor was successfully started after 48days of operation.A small amount of denitrifying bacteria and anammox bacteria synergistically denitrified the system,and the total nitrogen removal rate of the reactor was close to 100%.The results showed that AI-2 activating factor?boron?can increase the start-up speed of anammox reactor.?3?Comprehensively comparing gel ball appearance,pore structure,strength,and COD release rate,it was concluded that the optimal PVA and SA concentration for the prepared gel ball was 7%and 1%,respectively.Under these conditions,the particle size of the gel ball is approximately 4 mm,the density is approximately 1.0471 g/cm3,the specific surface area is 24.233 m²/g,the average pore size is 60.895 nm,and the distribution of pores is mainly macropores and mesopores.So the gel ball has good thermal stability and rich pore structure and is suitable for use as a suspension carrier in water treatment.?4?The start-up and running tests of Anammox-SBBR process show that:The actual nitrogen volumetric load of the reactor can reach 1.164g N/?L·d?,the total nitrogen removal rate is 93.92%,and the anaerobic ammonia oxidation activity?SAA?is measured as 5.86mg N·g^-1 VSS·h^-1.During the run phase of the gel ball filming,anammox bacteria were inhibited due to the increase of COD concentration in the early stage.However,as the COD concentration returned to normal,the anammox bacteria released their inhibitory activity.On the 237th day,the reactor recovered better nitrogen removal effect,the total nitrogen removal rate was 99.92%,and the measured anammox activity was 8.99 mg-N·g^-1 SS·h^-1.At the same time,the signal molecule AI-2concentration was measured to be 0.762 ng/mL.?5?Scanning electron microscopy?SEM?and high-throughput sequencing methods were used to analyze the sludge and biofilm characteristics and bacterial composition during start-up of anaerobic ammonia oxidation SBBR reactors.The results showed that the dominant bacteria in the reactor were Proteobacteria?14%?,Planctomycetes?24.21%?and Chloroflexi?23.67%?.Among them,Chloroflexi is dominated by Anaerolineales,a filamentous anaerobe.It is closely related to sludge granulation and biofilm formation.Three known Anammox bacteria in Planctomycetes brocadiales were detected in the reactors:Candidatus Jettenia,Candidatus Brocadia,and Candidatus Kuenenia.Among them,the main ones are Candidatus Jettenia.