Abstract: Utilizing the unique vertical aerobic-anoxic-anerobic ecological enviornment of landfills and adopting intermittent aeration at the top of landfilled refuse,this paper studied the performance of leachate nitrogen removal in the bioreactor landfill system.The results showed that intermittent aeration at the top of landfilled refuse could stimulate the growth of nitrifying and denitrifying bacteria.The population of denitrifying bacteria was 4～13 orders of magnitude higher than that in conventional landfilled waste layers,and the maximal value of nitrifying bacteria population reached 10⁹ cells·g^-1.The bioreactor landfill system with intermittent aeration at the top of landfilled refuse increased the potential of nitrogen removal from re-circulated leachate in the landfill bioreactor.By the end of the experiment，the concentrations of leachate NH₄⁺-N and total nitrogen (TN) decreased to 186 mg·L^-1 and 289 mg·L^-1,being only 18% and 26% of control,respectively.Intermittent aeration at the top of landfilled refuse also accelerated refuse decomposition,and increased the degree of waste stabilization.

Key words: Competition, Fraxinus mandshurica, Larix gmelini, Pure stand, Mixed stand