PRODUCED WATER FROM SHALE GAS PRODUCTION: ORGANIC SUBSTANCES AND TOXICITY TESTING

Depending on volumes and quality, produced water from gas extraction in shale is a possible environmental and human health issue as a result of improper disposal, leakage, fluid spillage or other events that allow for untreated fluid release into the surface environment. Organic substances, salinity, radionuclides, trace elements, and hydrocarbons present to varying degrees in shale gas produced waters may be environmentally relevant. Although lists of organic chemicals used in hydraulic fracturing are available, few studies of the organics present in produced water from shale gas extraction operations have been published. Also few studies of the potential toxicity of shale gas produced waters have been conducted.

We examined organic substances in produced water from the Marcellus and New Albany Shales, and the effects of produced water from the Marcellus Shale on commercial human kidney cell lines (HK-2). In formation water from the New Albany Shale (no hydraulic fracturing chemicals) total organic carbon (TOC) levels averaged 8 mg/L, and organic substances included: long-chain fatty acids, alkanes, polycyclic aromatic hydrocarbons, heterocyclic compounds, alkyl benzenes, and alkyl phenols. Flowback water from Marcellus Shale wells had TOC levels as high as 5,500 mg/L, and contained a range of organic chemicals including, solvents, biocides, scale inhibitors, and other organic chemicals at thousands of µg/L for individual compounds. These chemicals and TOC decreased rapidly over the first 20 days of water recovery as injected fluids were recovered, but residual organic compounds (some naturally-occurring) remained up to 250 days after the start of water recovery (TOC 10-30 mg/L). Effects of produced water from the Marcellus Shale at full-strength and 1:10 dilution on a human kidney cell line were observed for most samples, perhaps from a combination of hypersalinity, organics, and metals. Significant wound closure inhibition in kidney cell mats occurred, and arylhydrocarbon receptor (AhR) proteins were increased (upregulated relative to controls) at up to 1:100 dilution. AhR is a transcription factor activated by organics (aryl hydrocarbons). Ongoing studies will attempt to isolate the impacts of hypersalinity and other constituents (organic and inorganic) from produced water on human cell lines.