­­IMPACT OF UNCONVENTIONAL GAS WASTE WATER DISPOSAL ON SURFICIAL STREAM MICROBIOLOGY

The development of unconventional natural gas resources has been rapidly increasing in recent years, however, the environmental impacts and risks are not yet well understood. A single well can generate millions of liters of produced water (PW), a mixture of brine from the fractured shale formations and injected hydraulic fracturing fluid (HFF). With thousands of wells completed in the past decade, safe management of PW has become a major challenge to industry and regulators. One method for the disposal of PW is underground injection; to assess potential risks posed by injection and unintentional releases from injection facilities we are performing an intensive, interdisciplinary study of an Underground Injection Control (UIC) facility in the Wolf Creek watershed in WV. In June 2014, we sampled a tributary of Wolf Creek which originates above the facility, before running through the facility and adjacent to former holding ponds (closed in spring 2014). Water and bed sediment samples were taken upstream, within, and downstream of the facility. Field measurements and laboratory analyses provided a first indication of PW impacts to the stream, including elevated conductivity and elevated Cl^- and Br^- concentrations. 16S rRNA gene sequencing revealed that the microbial communities present in bed sediments adjacent to the former ponds are markedly less diverse than communities found at the other stream sites. As microbially driven processes control the fate and transport of both organic and inorganic components of PW, we designed a series of microcosm experiments to assess the influence of HFF/PW components (including biocides, anti-scale additives, gelling agents, and high TDS) on microbial community composition and metabolism. Initial analyses suggest a greater potential for anaerobic metabolism in sediments from the impacted site compared to the background site. In addition, these microcosms indicated that Fe reduction decreases with the addition of biocides, but increases in the presence of other organic HFF components. Our findings demonstrate the potential for releases from a PW disposal facility to alter microbial communities and biogeochemical processes. We anticipate that these studies will be a useful model for the potential impact of a PW disposal facility on adjoining surface- and shallow groundwater.