Researchers from the Massachusetts Institute of Technology (MIT) and Saudi Arabia's King Fahd University of Petroleum and Minerals said they have found an economical solution for removing salt from water produced when hydraulically fracturing (frack) oil and natural gas wells, according to a paper published this week in the journal Applied Energy.
The method proposed for treating produced water by MIT's John Lienhard and his five co-authors, electrodialysis, has been available for decades but has not been considered a viable candidate for extremely high-salinity water.
"Electrodialysis is generally thought of as being advantageous for relatively low-salinity water," said Lienhard, but the team's research indicates that high-salinity water produced during fracking can be effectively treated through a succession of stages of electrodialysis. The water could be cleaned up enough to enable its reuse in fracking operations, significantly reducing the amount of water needed from other sources, they said. The water could not be cleaned to the point that it would be potable. Prior to desalination, chemical impurities in the water would need to be removed using conventional filtration.
The costs of installing an electrodialysis system appear to compare favorably to other widely used systems for dealing with produced water, according to the researchers. But there are still hurdles to be cleared before the process can be put into use. While electrodialysis technology is already available, the application would require the development of some new equipment. And the researchers aren't certain how well the membranes used for electrodialysis would hold up following exposure to water containing traces of oil or gas.
Another technology developed at MIT -- carrier gas extraction -- was put into use this summer at a water desalination plant in the Permian Basin in Texas (see Shale Daily, July 11). That technology, which involves humidification, dehumidification and desalination, processes up to 12,000 barrels per day of produced water from oil and gas drilling.