Study On The Anammox Immobization Technoligy

Anaerobic ammonium oxidation(Anammox)process is a new type of biological denitrification process.Compared with the traditional denitrification process,it has the advantages of less energy consumption,high denitrification efficiency,and no need for additional carbon source.However,due to the long doubling time of Anammox bacteria and its sensitivity to changes in the external environment,the start-up time of the Anammox process is long,which hinders its development.The partial nitritation/anammox(PN/A)process developed based on Anammox,as a fully autotrophic nitrogen removal process,has attracted widespread attention due to its excellent nitrogen removal effect.However,how to provide favorable conditions for the symbiosis and highefficiency synergy of aerobic ammonia oxidizing bacteria(AOB)and Anammox bacteria in the system is an urgent problem to be solved.Microbial embedding and immobilization technology traps free microorganisms in a limited area to keep them active.This study combined the microbial cell immobilization technology with the Anammox and PN/A processes,which can provide a suitable environment for the growth of Anammox and AOB bacteria.The combination will effectively enhance the treatment effects of the two processes,and had considerable engineering value.The research results are as follows:The effect of PVA concentration on immobilized Anammox pellets were studied.A higher concentration of PVA could reduce the adverse effects of the production process of immobilized Anammox pellets on microbial apoptosis to a certain extent.The characteristics of immobilized pellets made of different PVA concentrations were explored,and the pore diameters were mainly distributed in 10nm-100?m;PVA/SA(5%/2%)immobilized pellets had the strongest mechanical stability.However,the denitrification effect of different kinds of immobilized pellets after short-term experiment was not much different.After short-term experiment,Anammox bacteria became the dominant bacteria in the immobilized pellets.After correlation analysis,PVA/SA(12%/2%)was selected as the carrier for the next long-term culture.This study conducted a shor-term comparison experiment of PVA/SA(12%/2%)immobilized pellets and Anammox granular sludge.Compared with granular sludge,Anammox immobilized pellets had higher nitrogen removal efficiency,but the mechanical stability of the embedded particles decreased with time during operation.The EPS in the immobilized pellets made the combination of microorganisms and the carrier closer.16 S high-throughput sequencing showed that the abundance of Anammox bacteria was increased after culture,and the immobilizing promoted the growth of Anammox bacteria.Two new PN/A co-immobilization methods were developed.After 12 days of experiment,the total nitrogen removal rate of spherical and square PN/A co-immobilized pellets reached 88.43% and 87.21%,respectively.The EPS content and composition structure changed too.The pore diameters of the two kinds of co-immobilized pellets were mainly distributed in 10nm-40?m,and had strong mechanical stability.But the square co-immobilized pellets were more rigid.Spherical co-embedded particles had higher value of porosity,pore surface area,and pore volume,while square coimmobilized pellets had higher value of median pore size and better connectivity between pores.AOB bacteria and Anammox bacteria are well fixed in the outer layer and inner structure,respectively.