The study of landfill microbial communities using landfill gas and landfill gas condensate

Abstract

Landfills are today the most widely used form of municipal solid waste (MSW) disposal. A better understanding of the waste decomposition process is important to improving waste disposal systems. Landfills are extremely heterogeneous, and as a result, conventional grab sampling of waste can only provide a limited understanding of this microbial community. In this study, landfill gas and gas condensate were used, which allowed collecting samples without disrupting the waste. Samples were collected from the Burlington County Resource Recovery Complex, NJ. Cells from landfill gas were collected on membranes by vacuum from existing gas extraction wells. Microbial communities were studied by using PCR amplification and slot-blot hybridization with 16S rRNA-targeted oligonucleotide probes. This study found that in all three media (landfill gas, gas condensate, and waste), Bacteria dominated in the landfill populations. The relative abundance of Bacteria found by hybridization was approximately 86-87%. Also, bacterial 16S rRNA was detected throughout all landfill samples, except in one of the gas samples analyzed by PCR amplification. Quantitatively, Archaea seemed to be a minor component of the microbial community at the landfill despite their significant functional role. The relative abundances of Archaea were 7.2 % and 2.1 % in gas condensate and in waste, respectively, while they were not detected in the gas. However, limited sample volume may be responsible for non-detection in the gas. By PCR amplification analysis, archaeal rRNA was detected in the gas condensate and wastes, but not in the gas. Methanogens were identified only in the landfill gas condensate and in one waste sample. Eucaryotic rRNA was only detected in landfill wastes, where their relative abundance was 13%. A literature review suggested that no prior study has investigated the landfill microbial communities by using landfill gas or gas condensates. The present study suggests that gas and gas condensates could provide representative samples from the landfill environment. The results from this study should provide a foundation for study of the microbial ecology in landfills.%%%%Ph.D., Environmental Engineering – Drexel University, 2002