Effect of aeration on the treatment of aged landfill leachate by a composite biofilter and its microbial community structure

Two different media, aged refuse and waste porous filter material, were used to construct composite biofilters. Their treatment efficiencies on mature landfill leachate pollutants under different operating conditions were investigated. The microbial number, composition and structure of functional micro-organism under different aeration conditions, and their relationship with the treatment effects were analyzed. The results showed that the aeration could enhance the pollutant removal significantly. COD, NH₄⁺-N and the TN removal rates with aeration were respectively 10%, 30% and 10% higher than without aeration. Additional aeration had no further influence on pollutant removal. Micro-organism counting showed that the number of bacteria at the top of both aerated and non-aerated stages were higher than that at the bottom. In the upper part, the number of heterotrophic bacteria and nitrifying bacteria significantly increased, nitrite bacteria significantly reduced, and denitrifying bacteria did not change much. Obvious changes in both the number and brightness of the sequencing results of PCR-DGGE bands from aeration to non-aeration indicated that the structure of the microbial community is closely related with the aeration. The result also showed that the major microbial colonies in the bioreactor had high similarity with Proteobacteria and others.