| The features of mature landfill leachate is low organic content, poor biodegradability, high ammonia concentration as well as low the C/N ratio which make it hard to deal with. Aged refuse has the unique physical and chemical properties and abundant microorganism community, and bioreactor packed with aged refuse could enhance the leachate pollutants transformation and degradation. It is a simple biological treatment technology and have potential widely application. However, some pollutants removal efficiency of the technology have space to improve.The microorganism groups in the aged refuse bioreactor plays an important role in the leachate pollutants removal, however the research of microorganisms in the bioreactor is little studied previously, especially the microbial community in nitrogen removal process of mature leachate is rarely reported.In this paper, the aged refuse in Shanghai laogang landfill and waste porous filter material were used as carriers to build aged refuse bioreactor, complex refuse bioreactor and aged refuse anaerobic ammonium oxidizing (ANAMMOX) bioreactor. The effects of different operating conditions of the bioreactor by adjusting temperature, hydraulic loading recirculation ratio and plus carbon source, the treatment effect of mature landfill leachate was studied, and the microbial community structure was investigated by molecular denaturing gradient gel electrophoresis (DGGE) technique, the relationship between pollutants removal efficiency and the microbial community structure were studied as well, which could provide a basis for optimizing the operation of mature leachate treatment. Conclusions were drawn as follows:1. The conclusion of biological reactors in15℃were drawn as follows:1) When the hydraulic loading of aged refuse bioreactor and complex refuse bioreactor were at8.5L/(m3·d), there’s no difference between two bioreactors in NH4+-N, BOD5,TN and CODCr removal rate. The result of bacterial diversity by DGGE was showed that the bacteria community structure of different bioreactor and different sites were quite different. The difference of microbial community structure was mainly due to different filler and heighter of the bioreactor.2) With the hydraulic loading of complex refuse bioreactor was raised (from8.5L/(m3·d) to17L/(m3·d)), its TN removal rate increased, while its NH4+-N, BOD5and CODcr removal rate remained the same. The result of bacteria community structure by DGGE showed that bacteria diversity in the upper region was increased, and little change in region of bottom. The result showed that the increasing organics load by hydraulic loading has the influence on the bacterial community structure, and complex refuse bioreactor had a strong ability to hydraulic loading shock.3) Compared with the hydraulic loading of aged refuse bioreactor was17L/(m3·d), when the recirculation ratio was100%, the NH4+-N, BOD5, TN and CODcr removal rate were no difference. The bacteria community structure in the upper bioreactor were similar. The result showed that this recirculation ratio has little effect on bacteria community structure in the aged refuse bioreactor. When the recirculation ratio was200%, the TN removal rate was increased, while the CODcr removal rate was decreased and NH4+-N and BOD5removal rate were no difference. The bacteria diversity in the upper and lower region were decreased. The result showed that this recirculation ratio has influence on bacteria community structure, and the bacteria divisity was decreased.4) When carbon source was added to the the complex refuse bioreactor, the TN removal rate was increased, while the CODCr removal rate was decreased. The bacteria community structure in the upper region were changed while the bottom had little change. The result showed that carbon source addition had effect on bacterial community structure, and lead change to the TN removal rate.2. The conclusion of biological reactors in30℃were drawn as follows:1) When the hydraulic loading of aged refuse bioreactor and complex refuse bioreactor were34L/(m3·d), there’s no difference between two bioreactors in NH4+-N, BOD5, TN and CODCr removal rate. The result of bacterial diversity by DGGE were showed that the bacteria community structure and nitrifying bacterial community structure in the upper site were similar between two bioreactors, while the lower site had small change. This might be due to the result of the long-term domestication.2) When the hydraulic loading of ageed refuse bioreactor raised (from17L/(m3·d) to34L/(m3·d)), the CODCr removal rate was decreased, while the NH4+-N, TN and BOD5removal rate remained the same. The result of bacteria community structure by DGGE were showed that bacteria diversity in the upper region was decreased, and little change in lower site. The result showed that the increase of hydraulic loading had influence on the bacteria community structure, and aged refuse bioreactor had a general ability to hydraulic loading shock.3) Compared with the hydraulic loading of aged refuse bioreactor was34L/(m3·d), when the recirculation ratio was100%, the NH4+-N removal rate was decreased, while the CODCr and TN removal rate were no difference. The nitrifying bacterial divisity in the upper site were decreased, and the bacterial divisity in the lower site were changed. The result showed that this recirculation ratio has effect on microbial community structure in the aged refuse bioreactor. When the recirculation ratio was200%, the NH4+-N and CODCr removal rate were decreased, while TN removal rate was kept the same. The nitrifying bacterial divisity in the upper site decreased, while little change in the lower site. The result showed that the increase of hydraulic loading had impact on the microbial community structure in different region of bioreactor, and result in the organics removal efficiency, however the recirculation could dilute the concentration of the pollutants, and led to the low concentration of effluent.In aged refuse bioreactor and complex refuse bioreactor, the major bacteria microbal colonies were Proteobacteria、Firmicutes、Bacteroidetes and uncultured bacteria, the major nitrifying bacterial colonies are Betaproteobacteria and uncultured bacteria.3. The conclusions of the aged refuse ANAMMOX bioreactor were drawn as follows:1) When the TN hydraulic loading of aged refuse ANAMMOX bioreactor was among0.95g(TN)/kg(vs)·d and2.03g(TN)/kg(vs)·d, the TN removal efficiency was between65%and96%Under the above conditions, there was little change in bacterial community structure. The major bacteria microbal colonies were Proteobacteria, Bacteroidetes, Cytophagaceae and uncultured bacteria, which were mostly found in extreme environment, such as petroleum-contaminated soil, ocean, lake, radioactive contaminated area, and higher aliphatic hydrocarbon content area, most of them had the ability to endure harsh environmental conditions.The result showed that after a long-term acclimation, the organics removal efficiency had no difference between aged refuse bioreactor and complex refuse bioreactor, and the microbial community structure was close between two bioreactors. When the recirculation ratio was increased, the NH4+-N and CODCr removal rate was decreased, as well as the microbal diversity. High recirculation had the strong impact on the organics removal effiency, and resulted in the decreased of organic removal rate. When carbon source was added to the bioreactor, TN removal rate was increased, and the bacteria community structure changed as well. When the influent TN loading of aged refuse ANAMMOX bioreactor increased, the TN removal rate decreased, while there was little change in bacteria community structure, the nitrogen removal function microbial community in the reactor need to be further studied in the future. |
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