Research On Anammox-AGS Process Characteristics And Control Based On Quorum Sensing

Granular sludge is a granular microbial aggregate composed of a large number of bacteria and bacteria secreted substances,as well as inorganic substances.Compared with flocculated sludge,granular sludge has advantages in overall appearance,settling performance,impact resistance,biomass and mechanical strength.However,the formation of granular sludge is a complex process in which microorganisms interact with the external environment,and is affected by inoculated sludge,substrate composition,organic load,reactor type,and operating mode.Therefore,the formation mechanism of granular sludge and how to speed up the cultivation of granular sludge have become research hotspots in recent years.The formation of granular sludge is also related to the interaction between microorganisms in the system.For example,the density sensing signal system possessed by microorganisms has a certain regulating effect on the formation of granular sludge.Quorum sensing?QS?means that microorganisms secrete and release a signal molecule called autoinducer?AI?into the environment,and they can diffuse freely between cells.Bacteria monitor the number of surrounding bacteria by sensing the concentration of signal molecules.When the bacterial density exceeds a certain threshold,it stimulates the expression of related genes in the bacteria,coordinates the physiological behavior of the flora,and regulates the functions of the ecosystem.Based on the mechanism of action of QS and signal molecules,this study realized the rapid cultivation of anammox granular sludge?AnGS?and aerobic granular sludge?AGS?.At the same time,the nitrogen removal performance,addition,the substrate inhibition kinetic characteristics,mass transfer performance and bacterial group structure of the two granular sludges cultivated based on the QS mechanism were studied by various methods.?1?A certain amount of flocculent Anammox sludge was placed in the Up-flow anaerobic sludge bed?UASB?.Then,the Bio-flow separate ball was placed in the reactor to change the spatial position of the sludge,and the QS of Anammox sludge and sludge granulation were studied.The results showed that the density of AnAOB increased rapidly at the local location after adding the Bio-flow separate ball,which triggers the QS of bacteria,strengthens the biological aggregation behavior of bacteria,and accelerates the formation of granular sludge.After 70 days of cultivation,AnGS with a particle size of 1to 3 mm was obtained,the removal rate of total nitrogen was more than 85%,the total nitrogen volume load was 0.72 kg·?m³·d?^-1,and the denitrification performance was good.?2?The Haldane model was used to study addition,the substrate inhibition kinetic characteristics of AnGS cultured based on quorum sensing.The kinetic results show that the maximum reaction rates of AnGS to NH₄⁺-N and NO₂^--N are 1.46 kg·?kg·d?^-1 and 1.76kg·?kg·d?^-1,respectively,and have higher nitrogen removal efficiency.The half-inhibition constants?K_i?of NH₄⁺-N and NO₂^--N are 852.2 mmol·L^-1 and 108.2 mmol·L^-1,respectively,which can withstand higher matrix concentrations and is conducive to the stable operation of the reactor.At low concentrations,the increase in the concentrations of NH₄⁺-N and NO₂^--N can promote the progress of Anammox;at high concentrations,the continued increase in the matrix concentration will instead inhibit the reaction rate of Anammox,and high concentrations of NO₂^--N are easier to suppress Anammox reaction.?3?In the sequencing batch reactor?SBR?,the effluent from the Anammox process of granular sludge containing multiple signal molecules is used as a biocatalyst to trigger the QS of microorganisms in aerobic sludge.By examining the changes of AGS morphology,nitrification performance,extracellular polymer,etc.,the effect of QS on the aerobic sludge granulation process was explored,and the effect of multiple signal molecules on the microbial structure was analyzed.The results showed that signal molecules can be transmitted between species and play a role,effectively stimulating the quorum sensing of the bacteria in aerobic sludge.The average diameter of AGS increased rapidly from 0.5mm to 3.5 mm within 20 days,the content of extracellular protein?PN?and extracellular polysaccharide?PS?increased from 187.7 and 45.7 mg/g VSS to 330.5 and 62.9 mg/gVSS respectively,and the ammonia utilization rate?AUR?from 3.41 increased to 5.96 mgNH₄⁺-N/?g VSS·h?.The richness of the community increased and the diversity decreased,Nitrosomonas?31.7%?became the new dominant bacteria.These findings will provide new ideas for the cultivation of granular sludge and the optimization of microflora,and have a positive impact on the redesign of the simultaneous short-path nitrification/Anammox?SPN/A?process and the coupling of other processes.?4?The mass transfer performance of AGS has a great influence on the actual operation efficiency of the AGS process.Thus,the mass transfer performances of AGS over different particle size ranges was studied by measuring the effective diffusion coefficients?D_e?,and the pore size distribution of AGS was analysed by BET pore size analysis.The results showed that AGS in the range of 2.0-3.0 mm had the best mass transfer performance,with D_e values of ammonia nitrogen and oxygen of 0.945×10^-9 m²/s and0.678×10^-9 m²/s,respectively.Pores with a radius of 16-120 nm occupied a larger proportion than AGS in other particle size ranges,and the largest proportion was pores with a radius of 120-260 nm.The BET surface area reached 117.019 m²/g,which was significantly higher than that of AGS in other particle size ranges and had a stronger adsorption performance.Fluorescent sections of AGS were observed by confocal laser scanning microscopy.The AGS in this particle size range had a reasonable distribution of cells,PN and PS and good mechanical strength.