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Abstract
A novel biocover with passive air diffusion system (PADS) was designed in this study. Its effect on landfill gas components in the macrocosms of simulated biocover systems was also investigated. The results show that O2 concentration increased in the whole profile of the macrocosms equipped with PADS. When simulated landfill gas (SLFG) flow rate was no more than 40 mL min−1, the methane oxidation rate was 100%. The highest CH4 oxidation capacity reached to 31.34 mol m−3 day−1. Molecular microbiology analysis of the soil samples taken from the above macrocosm showed that the growth of type I methanotrophs was enhanced, attributable to enhanced air diffusion and distribution, whereas the microbial diversity and population density of type II methanotrophs were not so affected, as evidenced by the absence of any difference between the biocover equipped with PADS and that of the control. According to a phylogenic analysis, Methylobacter, Methylosarcina for type I, and Methylocystis, Methylosinus for type II, were the most prevalent species in the macrocosm with PADS.
Semiaerobic landfill technology was reported to be an effective in situ CH4 emission reduction method. A semiaerobic status is achieved through a continuous supply of fresh air sucked passively through the open end of a leachate collection pipe, with a temperature gradient created by organic matter degradation. In this research, a novel passive air diffusion system (PADS) was designed, and O2 concentration increased in the whole profile of the microcosms equipped with PADS. The constant supply of fresh air reduced CH4 production and enhanced biodegradation. Through molecular microbiology analysis, it was found that growth of methanotrophs was enhanced, and species of prevalent methanotrophs were found.
Supplemental materials are available for this article. Go to the publisher's online edition of the Journal of the Air & Waste Management Association for a list of abbreviations and PCR protocol.
Acknowledgments
This research project was funded by the National High Technology Research and Development Program of China (grant no. 2007AA06Z350) and the National Natural Science Foundation of China (grant no. 41101225).