| Landfill is the technology used most widely to dispose the solid refuse relative to composting treatment and waste incineration. The leachate it generates will cause serious pollution to the environment. The "MSW Landfill Pollution Control Standard" (GB16889-2008) promulgated recently not only has stricter limits for leachate COD, BOD5, ammonia nitrogen, suspended solids and E. coli, etc., but also defines the standards for the discharge of the total nitrogen, total phosphorus and heavy metals. In order to meet the new emission standard, the traditional landfill leachate treatment technologies faced more severe challenges. Therefore, the research on landfill leachate treatment has important practical application value.Age-refused bioreactor is a new technology for the leachate treatment. It uses the aerobic microorganisms on the upper surface and the anaerobic microbial on the lower surface, in combination with particles adsorption, ion exchange and chelation to remove the pollutants. The main operating mechanism was water adsorption dry degradation. Age-refused bioreactor has good treatment effect of the leachate, especially of the fresh leachate. And it has been widely applied in practical engineering. But there were few studies on the old leachate treatment with the use of the age-refused bioreactor..In this paper, the aged refuse in Shanghai laogang landfill and waste porous filter material were used as carriers to build aged refuse bioreactor, and the old landfill leachate was treated by the bioreactors in this later year. The effects of different operating conditions of the aged refuse bioreactor by adjusting inflow and aeration was studied; based on the analysis of bacteria community structure in different operating conditions, the relationship between areation and the microbial community structure, as well as the relationship between treatment effects and the microbial community structure were studied; by combining the effluent status and PCR detection, the possible way of nitrogen removal was analysed, conclusions were drawn as follows:(1) Under same hydraulic loading rate, influent frequency had little impact on the pollutants removal. The COD, NH3-N and the TN removal rate were 39%,53% and 24% respectively in the operation of 3 times a day, in the operation of 6 times a day, the COD, NH3-N and the TN removal rate were 41%,58% and 25% respectively.(2) The aeration could enhance the pollutants removal significantly. The COD, NH3-N and the TN remove rate were 10%,30%,10% higher than those of non-aeration. Increasing aeration did small influence on the pollutants removal. On the one hand, aeration can improve the aerobic environment for heterotrophic bacteria and nitrifying bacterial growth; on the other hand, aeration can create anaerobic-anoxic conditions, it's conducive to the removal of pollutants. Reduce the loading rate through the series, the removal of pollutants enhanced obviously, especially for the removal of COD and ammonia nitrogen, indicated that hydraulic retention time have a great impact on the removal of refractory pollutants, but it did little impact on the total nitrogen removal.(3) The number of bacteria in the upper of both aeration stage and non-aerated stage were higher than that in the bottom. The number of heterotrophic bacteria and nitrifying bacteria in areation stage were more than that of non-aeration by an order of magnitude, while the change of denitrifying bacteria was not obvious. Extend aeration time can also increase the number of bacteria, but there was no orders of magnitude difference.(4) Aeration could change the bacterial community structure significantly, PCR-DGGE profiles showed the increase of bacterial diversity after aeration, also MVSP cluster analysis showed that the significance difference of bacterial community between aeration stage and non-aeration stage, however, increase aeration had less impact on the similarity.(5) Sequencing results of DGGE band showed that the major microbal colonies in the bioreactor were proteobacterium, Alcanivorax sp.521-1, unculturedβ-proteobacterium, Dechloromonas aromatica RCB and so on. These bacteria were often seen in the leachate and landfill study. Nitrifying bacteria are mainly uncultured ammonia-oxidizing bacteria.(6) The C/N was lower in mature landfill leachate, and the carbon source was lack for the denitrification, therefore, the total nitrogen removal efficiency was low. Since the anaerobic ammonium-oxidizing bacteria was not detected by PCR (Polymeric Chain React), combined the ammonia concentration changes in the atmosphere, the possible pathway of nitrogen removal in the aged refuse bioreactor was duduce to biological denitrification and ammonia volatilization.This study showed that by adjusting the reactor operating conditions, such as increasing air ventilation and decreasing hydraulic loading, were an effective strategies to enhance the pollutants removal.
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