| The urban household trash is increasing acceleratly with the high speedy economic development and urbanlization steps of China.According to the related statistics,one person can produce 1.2～1.4 kg trash per day in Chinese urban,about 440～500 kg per year.The whole urban household trash productions were reaching to 200 million ton in 2007 with the increasing rate of 8～10%per year,closed to the developed countries.Compared with the fertilizing and incinerating of household trash,the landfill treatment is the most popular measure,however,the landfill leachate may cause serious groundwater pollution.The newly published national "Standard for Pollution Control on the Landfill Site of Municipal Solid Waste"(GB16889-2008) has stricter standard of discharge of leachate in COD,BOD5,NH3-N,SS,E-coli,TN,TP and Heavy metal.It is difficulte to reach the new standard using traditional landfill leachate treatment technologies only.Some studies are essential on new treatment technologies for landfill leachate.In this paper,pilot biofilter reactors were built to study the removal efficiency of landfill leachate using Shanghai Laogang Landfill aged refuse and porous waste, while hydarulic and organic loading and temperature of each reactor changed at different stages.Microbal community structure of filters in each stage and 10 selected landfill leachate biodegrading strains from sediment of Laogang Landfill oxidation and facultative ponds were also studied.Following are the main conclusions of this paper:(1) Under the same hydraulic loading and temperature conditions(20℃),the removal efficiency of aged refuse reactor to TN,COD and NH3-N are 50%,60%and 70% respectively,while the removal efficiency of porous waste reactor are 15%,75% and 90%.When the temperature was 10℃,the removal efficiency of aged refuse reactor to TN,COD and NH3-N changed to 25%,50%and 30%,the removal efficiency of porous waste reactor changed to 15%,60%and 60%.The aged refuse reactor has higher TN removal efficiency and lower COD and NH3-N removal efficiency than porous waste reactor.(2) Under the circumstance of two times hydraulic loading as aged refuse and porous waste reactors,the removal efficiency of mixed filters reactor to TN,COD and NH3-N are 40%,60%and 70%at 20℃,the removal efficiency to TN COD and NH3-N changed to 30%,60%and 45%at 10℃.The removal efficiency of mixed filters reactor was higher compared with that of aged refuse and porous waste reactors,which indicated better treatment efficiency and lower temperature resistance.(3) The amount of heterotrophic bacteria and actinomyces is in amount of 106 and 105 cfu/g.D.W levels respectively of each reactor after 2 months running.The mixed filter has a great amount of heterotrophic bacteria and actinomyces,while the porous waste is the lowest;the amount of heterotrophic bacteria and actinomyces increased as the temperature reduction.The microbal biodiversity index of mixed filters is higher than that of the aged refuse,the microbal biodiversity index also increased as the temperature reduction.The reasons are still under studying.(4) The major microbal colonies of the filters are uncultured proteobacterium and bacterium,such as unclutured bacterium,uncultured bacilli bacterium, uncultured Escherichia sp,uncultured delta proteobacterium,uncultured gamma proteobacterium.The microbal community structure similarity of mixed filter and aged refuse is 58%at 20℃,48%at 10℃respectively,while the microbal community structure similarity of same filters is 38%,which showed temperature impacts to community structure.The microbal community structure similarity of influent and each filter is only 25%,and the reason is the microbes changed great in the biofilters.(5) The BOD5:TN ratio of influent is lower(nearly to 1),the TN removal rate is weak through nitrification/denitrification mechanism because of the limited carbon source.The anaerobic ammonium-oxidation bacterials were not detected in Realtime PCR technology;based on the traditional culture counting of nitrosation/nitrification/denitrification bacterials;the TN removal mechanism is nitrification/denitrification or volatiled in this research,instead of anaerobic ammonium-oxidation.(6) Among the 10 selected microbials,5 of them have 50%COD removal efficiency, 3 are 30%,and 2 are lower than 30%.COD removal rate of the landfill leachate could improve 10-15%by adding mixed culture than the control one.Most of strains belong to Corynebacterium sp.By 16s rRNA identification some speices have the resistances such as drug resistances,which showed the capabilities of resisting terrible circumstance.
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