The Performance Stability And Microbial Characteristics Of Anaerobic Ammonium Oxidation Systems With Different Sludge Types Under Low Temperature

As a new type of biological nitrogen removal technology,the anaerobic ammonium oxidation process has the advantages of no need of oxygen consumption and additional carbon source,and less residual sludge production compared with the traditional nitrogen removal process.However,in the process of its popularization and application,due to the impact of low temperature,sludge loss and other problems,leading to the instability of the process operation.In view of the factors affecting the stable operation of the process,this study explored the impact of resistance and recovery ability of the anammox system with different sludge forms on different influencing factors by establishing the floccus and particle coupled anammox system?SBR1?and particle anammox system?SBR2?.Subsequently,in the two modes of instantaneous cooling and gradient cooling,the impact resistance and recovery ability of the system at low temperature were evaluated.Finally,combined with high-throughput sequencing method,the structural characteristics of microflora in anammox system with different sludge morphology were analyzed to explore the response mechanism of the system to a low temperature shock.The following main research conclusions were obtained:?1?The effects of dynamic sludge removal and shortening of standing time on the nitrogen removal performance of the system were investigated by setting up a flocculate-particle coupled anammox system and anammox particle system.After sludge inoculation,the removal rates of NH₄⁺-N and NO₂^--N in SBR1 on day 63could reach 99.49%and 97.74%,respectively.On day 80,the removal rates of NH₄⁺-N and NO₂^--N in SBR2 reactor could both be maintained at about 95%.On this basis,the effects of factors such as reaction cycle,standing time and sludge volume on the operating efficiency of the system were investigated.The experimental research found that the regulation measures such as bio-enhancement,artificial panning,adjusting the substrate concentration,and adjusting the reaction cycle can restore the system's nitrogen removal performance as soon as possible.?2?In order to explore the stability of the system under low temperature shock,gradient cooling?35??30??25??20??15??and transient cooling?35??15??were adopted.In the restorative test of the system,the NH₄⁺-N removal rate of SBR1 and SBR2 under transient cooling condition decreased by15.37%,22.63%,and the NO₂^--N removal rate decreased by 9.80%and 18.37%,respectively.The removal rates of NH₄⁺-N and NO₂^--N in SBR1 reactor with gradient cooling were reduced by 54.79%and 43.41%respectively.The removal rates of NH₄⁺-N and NO₂^--N in SBR2 reactor decreased by 64.81%and 43.74%respectively.In addition,after experiencing transient cooling and gradient cooling shocks,the nitrogen removal performance of SBR1 recovered basically after 4 h and 16 h respectively,and the recovery time of SBR2 operation effect was 12 h and18 h respectively.The results showed that there is a positive correlation between the recovery capacity of anammox system and the impact time at low temperature,and the nitrogen removal performance can be recovered more quickly in a system with multiple sludge forms coupled with the same condition.?3?In the restorative test of the system,the NH₄⁺-N removal rate of SBR1 and SBR2 under transient cooling condition decreased by 15.37%,22.63%,and the NO₂^--N removal rate decreased by 9.80%and 18.37%,respectively.The removal rates of NH₄⁺-N and NO₂^--N in SBR1 reactor with gradient cooling were reduced by 54.79%and 43.41%respectively.The removal rates of NH₄⁺-N and NO₂^--N in SBR2 reactor decreased by 64.81%and 43.74%respectively.Morever,after the transient cooling and gradient cooling shock of SBR1,the nitrogen removal performance of the system recovered basically after 4 h and 16 h,respectively,and the recovery time of the SBR2 system was 12 h and 18 h.The results showed that the recovery capacity of anaerobic ammonium oxidation system had a positive correlation with the duration of low temperature impact,and when the impact duration was the same,the system with multiple sludge morphology coupling can recover its nitrogen removal performance more quickly.?4?High-throughput sequencing results indicated that the microbial flora in the anaerobic ammonium oxidation granule system was higher than the flocculent-granule coupling system,while the anaerobic ammonium oxidation flocculent-granule coupling system had higher bacterial diversity than the granular system sample.In terms of microbial structure,at the level of phylum classification,the relative abundance of Planck tomycetes in SBR1 and SBR2 systems is 12.26%and 10.79%,respectively.Furthermore,at the classification level,three anaerobic ammonium oxidizing bacteria,Candidatus Kuenenia,Candidatus Brocadia and Candidatus Anammoxoglobus,were detected simultaneously in SBR1 and SBR2,totally accounting for 9.6%and 9.56%,respectively.Besides,their relative abundance was the highest,and anaerobics at other classification levels.Ammonia oxidizing bacteria abundance has certain advantages,indicating that anaerobic ammonium oxidizing bacteria are the main dominant bacteria in both flocculated-granule coupled anammox systems and anaerobic ammonium oxide granule systems and occupy a dominant position.