The large amounts of water required in the hydraulic fracturing of shales for oil or gas is a pressing concern. In hydraulic fracturing, water is sent down underground at high pressures to fracture the rocks below, allowing gas or oil to be released and captured. When water returns to the surface it often contains large amounts of salt that were dissolved from the rocks down below. These large quantities of salt have made it difficult to re-use the water for further fracturing processes – making it difficult to reduce water use by adopting recycling strategies.
Earlier this month, my co-authors, Adam Weiner, Lige Sun, Chester Chambers, Prof. Syed Zubair and Prof. John Lienhard and I published an article describing how electrodialysis can be used to remove salt from these waters to facilitate greater reuse. We were able to show that, compared to the evaporators are currently available to purify these waters, the system we proposed was of similar energy efficiency but more cost effective. We feel that electrodialysis, whereby salt is removed from water by means of an electrical current, is promising for this application – the next steps are to see how the system will fair in real world rather than lab conditions.