Commission warns Australia about gas-production wastewater

Handling the wastewater resulting from coal-seam gas (CSG) production in Australia is likely to require a precautionary approach that will demand innovation from water managers and planners, and significantly greater coordination with existing project approval processes, the National Water Commission warned in December 2010.

CSG production in the USA and Australia has required use and development of advanced wastewater treatment, such as reverse osmosis and mechanical vapour compression, to deal with the industry’s contaminated wastewater.

Current projections indicate the Australian CSG industry could extract in the order of 7,500 million m³ of co-produced water from groundwater systems over the next 25 years, equivalent to ~300 millon m³/year, says the commission in a position paper. By comparison, the current total extraction from the Great Artesian Basin is approximately 540 million m³/year.

The report warns of the following risks from the CSG extraction:

  • Extracting large volumes of low-quality water will impact on connected surface and groundwater systems.
  • Impacts on other water users and the environment may occur due to the dramatic depressurisation of the coal seam.
  • The production of large volumes of treated wastewater, if released to surface water systems, could alter natural flow patterns and have significant impacts on water quality, and river and wetland health. There is an associated risk that, if the water is overly treated, ‘clean water’ pollution of naturally turbid systems may occur.
  • The practice of hydraulic fracturing, or fraccing, to increase gas output, has the potential to induce connection and cross-contamination between aquifers, with impacts on groundwater quality.
  • The reinjection of treated wastewater into other aquifers has the potential to change the beneficial use characteristics of those aquifers.
  • “An adaptive and precautionary management approach will be essential to allow for progressive improvement in the understanding of impacts, including cumulative effects, and to support timely implementation of ‘make good’ arrangements,” the commission advises.

    The report makes 11 recommendations including licensing, monitoring and aquifer reinjection.

    “The consequences of not managing the water risks and uncertainties associated with the economic benefits of CSG are substantial,” warns the commission.