Study On Treatment Of Landfill Leachate By Anaerobic Ammonia Oxidation System

Landfill leachate contains high concentration of ammonia nitrogen and organic matter.The traditional nitrificantion and denitrification process for landfill leachate treatment has the disadvantages of high energy consumption and cost.Anaerobic ammonia oxidation?ANAMMOX?has the advantages of high nitrogen removal efficiency,no need for additional organic carbon source,low energy cousumption,low sludge yield and no second pollution etc.It can be alternative of the traditional nitrification and denitrification process as a new biological denitrification process for landfill leachacte.However,due to the slow growth rate of anaerobic ammonia oxidizing bacteria,and the susceptibility to influent quality and operating conditions,the process have the problems of longer start-up cycle and the lack of stability in the actual application.In this study,ANAMMOX process was employed to treat landfill leachate,the rapid start-up,operation conditions and influencing factors of the process were investigated,as well as the denitrification properties of the reactor and the microbial community structure changes.In this experiment,the treatment of landfill leachate by ANAMMOX process was studied via a UASB reactor inoculated with partial nitrification and denitrification sludge.Artificial water was used as the influent initially.The ANAMMOX reactor was quickly start-up by increasing the total nitrogen loading rate in the reactor,under the condition of a constant HRT?15h?and pH?7.3?.The influencing factors and operating conditions of the process were investigated,and the reactor is operated to the optimum load.After that,the ANAMMOX reactor was operated with the real landfill leachate wastewater to investigate the performance of reactor including the nitrogen removal and stable operations.Meanwhile,Illumina Miseq sequencing was conducted to analyze the microbial community dynamics from the molecular level.Batch experiments were conducted to investigate the short-term toxicity of heavy metal ions on anaerobic ammonia oxidation particles.The experiment results show that UASB-ANAMMOX reactor has been successfully started after 91 days of operation,and the total nitrogen loading rate reaches 0.80 kg/m3/d.Under the same nitrogen loading rate,the optimum ratio of NH₄⁺-N:NO₂^--N in influent is1:1.32,which can effectively improve the effluent quality.After 108 days of operation,the HRT of the reactor was shortened to 2 hours,the total nitrogen removal rate was increased to4.94±0.24 kg/m3/d,and the NH₄⁺-N and NO₂^--N removal efficiency were above 95%.The microbial diversity and abundance of the system decreased from the initial stage?1d?to the stable operation period?210d?.At 210d,the relative abundance of Planctomycetes that belonged to ANAMMOX bacteria was 46.94%,while the Candidatus Kuenenia that belonged to the microbial community of ANAMMOX bacteria had the relative abundance of48.87%.After 260 days of operation,the total nitrogen loading rate and total nitrogen removal rate of the system were 7.58±0.22kg/m3/d and 6.11±0.26kg/m3/d,respectively.The NH₄⁺-N and NO₂^--N removal efficiency were 89.86±4.33%and 91.21±3.29%,respectively.The variable loading on 92d caused system instability,which was recovered after 10 days.The NH₄⁺-N and NO₂^--N removal efficiency were recovered back to 98.50%and 98.71%,respectively.After 260 days of operation,the microbial abundance increased and diversity decreased.The relative abundance of Planctomycetes decreased to 31.30%.Relative abundance of Proteobacteria belonging to denitrifying bacteria and Chloroflexi belonging to heterotrophic bacteria increased to 29.10%and 22.50%,respectively.The relative abundance of Candidatus Kuenenia decreased,while that of denitrifying bacteria Limnobacter increased.At this time,the denitrification performance in the system was realized by anaerobic ammonia oxidation and denitrification,rather than a single anaerobic ammonia oxidation reaction.The results of batch experiment on short-term heavy metals toxicity to anaerobic ammonia oxidation particles showed that the nitrogen removal rate decreased obviously with the increase of heavy metal loading rate,but with the increase of exposure times,the nitrogen removal efficiency of ANAMMOX does not decrease,but tends to be stable.