ORGANIC SUBSTANCES IN PRODUCED WATER FROM UNCONVENTIONAL NATURAL GAS PRODUCTION - POTENTIAL HEALTH CONCERNS
In produced water from the coals, extractable organic compounds identified included: phenols, biphenyls, heterocyclic compounds, polycyclic aromatic hydrocarbons (PAHs), aliphatic hydrocarbons, and long-chain fatty acids. PAHs, such as naphthalene, phenanthrene, and their alkylated derivatives were the most prevalent compounds identified. Many more unidentified compounds are also present. Some identified compounds are toxic, but are unlikely to have acute health effects at the observed concentrations (0.1-10 µg/L). Chronic health and environmental effects from long periods of low-level exposure are unknown. In the Marcellus shale and overlying sandstone, extractable hydrocarbons in produced water include alkanes, biocides, anti-corrosion chemicals, ethylene glycol, and heterocyclic compounds. Many of the heterocyclics, and other identified organics (biocides, ethylene glycol) originate from chemicals added during hydrofracturing operations. The highest concentrations of organics and volumes of water from wells occurred in the first ten days following hydraulic fracturing in the flowback water. However, traces of hydrofracturing organic chemicals were seen in the produced water even months after hydraulic fracturing. Because many of these organic compounds are toxic, care should be exercised in the disposal of these fluids.