Research On The Start-up Of Short-range Nitrification And SPNA Process Based On Embedded Immobilization Technology

Compared with the traditional biological denitriication process,microorganisms are made into immobilized pellets and added into the reactor,which can effectively retain the biomass,prevent the loss of bacteria and accelerate the reaction efficiency.It has gradually become a research hotspot.In this paper,nitrifying sludge and anammox bacteria were respectively fixed in the carrier by embedded immobilization technology to study the ammonia nitrogen adsorption of immobilized pellets.At the same time,it explored the reactor start-up of partial nitrification and one-stage simultaneous partial nitrification anammox?SPNA?in continuous flow.In this work,exploring the characteristics and mechanisms of NH₄⁺-N adsorption by nitrifying sludge?NS?waterborne polyurethane?WPU?immobilized pellets was performed.The NH₄⁺-N adsorption by WPU immobilized pellets in different initial NH₄⁺-N concentrations,and the influences of temperature,pH,salinity on NH₄⁺-N absorption were respectively studied.Moreover,the adsorption isotherms,kinetics models and intraparticle diffusion model analysis were employed to investigate the adsorption process.The results showed nitrifying sludge WPU NH₄⁺-N adsorption capacity was higher than the pellets with no sludge?CK?,and it raised with the growth of initial NH₄⁺-N concentrations.Specifically,the optimal pH for NH₄⁺-N adsorption was 7.0;temperature and salinity had an inhibitory effect on the NH₄⁺-N adsorption.In addition,the NH₄⁺-N adsorption process by immobilized pellets was all conformed to the Langmuir and Freundlich isotherm.Meanwhile the process was in line with the pseudo-second-order kinetic model,which was combined by surface and internal diffusion.For the absence of research on immobilized pellets in continuous flow,active sludge was immobilized on a waterborne polyurethane?WPU?gel and used to inoculate a continuous flow reactor.After 70 days,the nitrite accumulation rate?NAR?was 96.94%when the operating dissolved oxygen?DO?was 1.8 mg/L and maintaining temperature at 25oC.The effect of different concentrations of DO on the stability of nitritation was investigated.NAR remained at 79.23%when increasing DO to 4.5 mg/L,indicating a good tolerance of changes in DO by immobilized pellets.High throughput was used to study the difference in the microbial communities between the beginning and the end of the start-up period.The results show that Nitrosomonas genus plays an important role on partial nitrification.Biological diversity and species richness also decreased with long time running.And the operation mode of human intervention has a selective effect on functional bacteria.In view of the water quality characteristics of low ammonia nitrogen and problems existing in traditional biological nitrogen removal technology,we integrated embedding immobilization with one-stage simultaneous partial nitrification anammox.After 42 days,the ammonia nitrogen removal rate was 87.82%when the operating dissolved oxygen?DO?was 1.8 mg/L and maintaining temperature at 25oC.By fitting the experimental data,it is determined that the effective diffusion coefficient of NH₄⁺-N in nitrifying sludge immobilized pellets is 0.313×10^-99 m²/s;and the effective diffusion coefficient of NH₄⁺-N in anammox immobilized pellets is 0.562×10^-99 m²/s.The phenomenon is mainly caused by the rejection effect and barrier effect of immobilized pellets.