Biological Nitrogen Removal Performance And Microbial Community Diversity Of ABR-oxidaton Ditch-BAF Treating Landfill Leachate

Landfill leachate is an organic wastewater with high concentration, which isgenerated from landfill site. It will cause serious environmental pollution if treatedinappropriately. As far, there is no any advanced, economic and typical process forthe treatment of landfill leachate. The newest national standard for pollution controlon the landfill site of municipal solid waste (GB16889-2008) came into effect in2008，the newly added emission limit on TN is now much stricter, making it moredifficult to meet the emission limit in the standard when treating landfill leachate. Inthis study, the treatment of simulatious early landfill leachate was invesitaged byusing a pilot-scale anaerobic baffled reactor (ABR)-integrated oxidationditch-biological aerated filters (BAF) combined process. Nitrification effluent fromoxidation ditch was recirculated to ABR with different recycle ratios and recyclepositions for TN removal without external carbon source. The running andbiological nitrogen removal performance of the system and each reactor wereinvestigated, and the microbial community diversity of sludge samples from eachreactor at stable stage were analyzed by Polymerase chain reaction and denaturinggradient gel electrophoresis (PCR-DGGE).TIN of influent was reduced from310.5～1279.0mg/L to23.5～223.1mg/L.In the late stage of the study, the removal ratio of TN was81.3%～97.5%, part ofTN values of effluent were no more than40mg/L, the minimum TN value ofeffluent was26.4mg/L. NH4+-N and COD of influent could be reduced from308.7～1278.1mg/L and1335.1～8032.9mg/L to0.6～58.7mg/L and20.5～197.1mg/L, respectively. ABR-integrated oxidaton ditch-BAF was a high efficientcombined biological treatment system. Nitrogen and organic matter could beremoved simultaneously by high recycle ratio and appropriate recycle position ofnitrificaiton effluent from oxidation ditch without external carbon source.The efficiency of biological nitrogen removal was almost100%when recycleratio was10and the influent COD/NO3--N value was more than5.0in the anaerobicpart of ABR. The denitrification accomplished completely when recycle ratio was 10and the influent COD/NO3--N value was more than4.0in the anoxic part ofABR, and the final effluent NOx--N was no more than15.0mg/L. Shortcut andconventional nitrificaiton-denitrification and ANAMMOX in ABR-integratedoxidation ditch and simulataneous nitrification-denitrification in BAF wereobserved.In the late three stage of the study, the common and particular microorganismswere observed in each reactor, and the microbial community which could utilize theinfluent substrate evolved to dominant populations. Overall, with the increase ofrecycle ratio, microbial community diversity in the first two chambers of ABR hadno significant change, but reduced in the rear three chambers of ABR, oxidatonditch and BAF. The similarity of microbial community between the first twochambers of ABR was high with high recycle ratio, as well as the rear threechambers, the similarity of microbial community among the rear three chambers,oxidaton ditch and BAF was higher than that among the first two chambers,oxidaton ditch and BAF. The high recycle ratio destroyed the phase separation ofacid-producing microorganisms and methanogens along ABR. Sequencing resultsillustrated that most of the microorganisms were uncultured bacterium andprotebacteria.