Aged landfill leachates become more refractory over time and difficulty to treat. Recently, aged refuse bioreactors show great promise in treating leachates. In this study, aged refuse bioreactors were constructed to simulate landfill leachate degradation process. The characteristics of leachate were: COD(cr), similar to 2200 mg/L; BOD(5), similar to 280 mg/L; total nitrogen, similar to 2030 mg/L; and ammonia, similar to 1900 mg/L. Results showed that bioreactor could remove leachate pollutants effectively at hydraulic loading of 20 L/m(3) d. The removal rate reduced when hydraulic loading doubled or temperature lowered. Effluent recirculation could alleviate the temperature effect. Combining aged refuse and slag biofilters could treat leachate more efficiently. Pyrosequencing analysis indicated that bacteria from Pseudomonas, Lysobacter, Bacillus and delta-proteobacter, Flexibacteraceae were more abundant in the samples. The Shannon index decreased at lower temperature, while evenness and equitability increased with recirculation. We suggest that filter medium and temperature may be the main factors for shaping bacterial community structure. Crown Copyright (C) 2011 Published by Elsevier Ltd. All rights reserved.