Chemical and bioanalytical assessment of coal seam gas associated water

Abstract

A comprehensive study was undertaken involving chemical (inorganic and organic) and bioanalytical assessments of coal seam gas associated water (CSGW) in Queensland, Australia. CSGW is a by-product of the gas extraction process and is generally considered as water of poor quality. CSGW is disposed of by release to surface water, reinjected to groundwater or beneficially reused. In this study, groundwater samples were collected from private wells tapping into the Walloon Coal Measures, the same coal aquifer exploited for coal seam gas production in the Surat Basin. The inorganic characteristics of these water samples were almost identical to the CSGW from the nearby gas field, with high sodium, bicarbonate and chloride concentrations but low calcium, magnesium and negligible sulfate concentrations. As for organic compounds, low levels of polyaromatic hydrocarbons (PAHs) were detected in the water samples, and neither phenols nor volatile organic compounds were found. Five of the fourteen bioassays tested gave positive responses (arylhydrocarbon-receptor gene activation, estrogenic endocrine activity, oxidative stress response, interference with cytokine production and non-specific toxicity), whereas the other nine assays showed no genotoxicity, protein damage or activation of hormone receptors other than the estrogen receptor. The observed effects were benchmarked against known water sources and were similar to secondary treated wastewater effluent, stormwater and surface water. As mixture toxicity modelling demonstrated, the detected PAHs explained less than 5 % of the observed biological effects. These results showed that bioanalytical assessment can open new avenues for research into the potential environmental and health risk from CSGW.