Identification of Pentachlorophenol (PCP) Tolerant Bacterial Communities in Contaminated Groundwater After Air-Sparging Remediation

Author(s): Stokes, C.; Prewitt, M.; Borazjani, H.

Pentachlorophenol (PCP), a highly toxic and recalcitrant wood preservative, contaminates groundwater aquifers in many areas of the United States. Improper handling, storage, and disposal practices in the past have led to the contamination of groundwater at many wood treatment facilities. Air sparging, the injection of clean air under pressure into the groundwater system, has emerged as a viable in-situ treatment option for removal of this type of contamination. Previous studies have relied on morphological studies for identification of the bacterial community that is responsible for PCP degradation. However, molecular identification of DNA extracted from the bacterial community present in the groundwater will provide a more accurate description of the microbial community. Groundwater samples from eight biosparging wells were taken quarterly and analyzed for total PCP concentration, nutrient content, and monthly samples were used for microbial identification. Microbial counts were taken for each well on selective media, and changes over time were compared between wells within the sparging wells’ zone of influence and wells not directly impacted by air sparging. PCP concentration was below 1 ppb and nutrient levels were within the normal range. Well 14 (above air injection) revealed Burkholderia sp., Denitratisoma oestradiolicum, Thauera sp., and Rhodoanobacter thiooxydans, along with >40 other species that were listed as "e;uncultured" in BLAST. Well 51 (below air injection), presented a greater variety of bacterial species than Well 14, including the known PCP degrader Flavobacterium, in addition to numerous "uncultured" species. DNA extracted from other wells is currently being sequenced and T-RFLP analysis is underway to provide a comparison over time of microbial communities between aerated and non aerated wells.

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