IMPACT OF UNCONVENTIONAL GAS WASTE WATER DISPOSAL ON THE STRUCTURE AND ACTIVITY OF SURFICIAL STREAM MICROBIAL COMMUNITIES

The development of unconventional oil and gas (UOG) resources has rapidly increased in recent years, however, the environmental impacts are not yet well understood. A single gas well can generate millions of liters of wastewater (WW), a mixture of brine produced from the fractured shale formations and injected hydraulic fracturing fluid. With thousands of wells completed in the past decade, safe management of UOG wastes, including WW, has become a major challenge to industry and regulators. UOG WW is commonly disposed of by underground injection. To assess potential environmental effects posed by surface releases from injection facilities we initiated an intensive, interdisciplinary study of an Underground Injection Control (UIC) facility in the Wolf Creek watershed in West Virginia. In June 2014, we sampled water and sediment along a tributary of Wolf Creek which runs through a UIC facility and adjacent to closed impoundments. Samples were taken upstream, within, and downstream from the facility. Field and laboratory measurements showed changes in the stream chemistry and changes in microbial communities downstream of the facility. Because microbially driven processes can control the fate and transport of organic and inorganic components of UOG WW, we designed a series of aerobic and anaerobic microcosm experiments to assess the influence of biocides, anti-scale additives, gelling agents, and high total dissolved solids (TDS) on microbial community structure and function. Analysis following incubation indicated that the microbial community structure shifted in response to these chemical inputs, with the strongest shift under aerobic conditions attributed to elevated TDS, and the strongest shifts under anaerobic conditions attributed to the addition of biocides. Community shifts were also noted in response to the addition of guar gum, an easily metabolized gelling agent. We noted that the biocide DBNPA inhibited iron reduction, demonstrating that both community structure and metabolism may be disrupted by UOG WW inputs. Our findings demonstrate the potential for releases from a UOG WW disposal facility to alter stream microbial communities and biogeochemical processes. We anticipate that these studies will be a useful model for the potential impact of a UOG WW disposal facility on adjoining waters.