INFLUENCE OF ORGANIC HYDRAULIC FRACTURING FLUID ADDITIVES ON THE ACTIVITY OF IRON-REDUCING BACTERIA IN A PRODUCED WATER IMPACTED STREAM

Very little is known about the environmental fate and influence of hydraulic fracturing fluid (HFF) constituents and produced water (PW). Microbes are known to affect the fate and transport of many environmental contaminants. We hypothesize that iron-reducing bacteria (FeRB) may mitigate organic pollutant impacts due to PW disposal or accidental releases to stream systems. A stream running alongside an oil and gas PW disposal facility in West Virginia has been impacted by disposal and storage operations, as indicated by elevated conductivity downstream relative to upstream of the site. In this study, we evaluated the potential for FeRB from impacted and unimpacted (upstream/background) stream sediments to grow in the presence of HFF components. FeRB were enriched from sediments in iron-reducer media with added amorphous FeOOH and either no donor, lactate, or a HFF additive: guar gum (a gelling agent), ethylene glycol (scale inhibitor), DBNPA or bronopol (both biocides). Iron reduction rates were positively influenced by additives that acted as a carbon source (lactate, guar gum, and ethylene glycol) and were negatively influenced by biocides. Reduction was consistently greater in cultures with sediment from the impacted site, most likely due to the increased Fe levels found in the sediment. Mineralogical differences between impacted and unimpacted sites, as well as changes in FeRB cultures were analyzed using XRD and VNIR spectroscopy. VNIR spectra indicated reduction of goethite (FeOOH) to greigite (Fe₃S₄) in active FeRB cultures. Cultures with low rates of reduction (killed controls and biocide-amended) remained primarily as goethite. We show that FeRB are present, potentially active, and likely acclimated to contaminants at a site impacted by PW and that their metabolism can be influenced by a variety of HFF components. Work is ongoing to assess microbial degradation pathways for HFF components and to identify the FeRB populations. We anticipate that these results will help contribute to a better understanding of the role played by FeRB in mitigating PW and HFF wastes.