Posted by: Footler PJ19 FEB 2014
The controversial process of hydraulic fracturing (“fracking”) involves injecting wells with large volumes of water containing various additives at high pressure to crack open deep shale deposits and extract natural gas trapped in the rock. One contentious issue is that up to 30 per cent of the water returns to the surface, bringing up high levels of salts, naturally occurring radioactive materials such as radium, and metals such as barium and strontium.
In theory, these contaminants should be removed before the water is reused or discharged into waterways. However, a study by Duke University in the Marcellus Shale gas field showed that standard treatment processes may only partially remove potentially harmful contaminants, causing radioactivity to accumulate in stream sediments near the disposal site.
The Marcellus Shale is a geological formation of shale rock buried deep under parts of Pennsylvania, New York and West Virginia. Unfortunately, the same area suffers with another problem in that highly toxic acid mine drainage from abandoned coal mines has contaminated hundreds of local waterways.
Following a suggestion that the acid mine drainage could be used to “frack” shale gas wells in place of fresh water, the researchers tried blending different mixtures of Marcellus Shale flowback and acid mine drainage. They examined the chemical and radiological contents using geochemical models, X-ray diffraction and measurement of radioactivity. They found that between 60 and 100 per cent of the radium and several ions such as sulphates, iron, barium and strontium had precipitated into solids, which are easier to remove leaving the treated water suitable for re-use in fracking.
The process still has to be tested in the field. Although it may not make fracking any more popular, two wrongs could actually make a right in the Marcellus Shale.