By Peter Chawaga
Two growing trends on the industrial and municipal sides of drinking water and wastewater treatment appear to be on a path toward collision.
As the practice of hydraulic fracturing — also known as fracking, in which high-pressure water streams are blasted into the ground to open up oil deposits — becomes more popular and the strain on available source water supplies becomes more acute, better treatment technology is becoming an imperative for both. There is a growing need for projects like SNOWater, a solar-powered water desalination technology pioneered by researchers at Rice University, that can turn wastewater at decentralized fracking sites and treat it to acceptable levels for recharge back into source supplies.
“In the U.S. alone, 40 million people do not have access to municipal water,” said Alessandro Alabastri, a postdoctoral research fellow at Rice who helped invent SNOWater. “In addition, the oil and gas industry produces 14 billion barrels of wastewater per year. Most of the existing water purification technologies require complex and costly infrastructures and rely on electricity or fossil fuels to function. Our portable and scalable, nanophotonics-based system efficiently exploits renewable solar radiation and targets dry, sunny regions with access to a water source.”
SNOWater utilizes a water-repelling membrane coated with carbon black nanoparticles capable of absorbing 95 percent of the sunlight that hits its surface. This carbon black surface generates heat and creates a localized temperature difference across the membrane, which in turn creates a vapor pressure difference that pushes saline water (like the byproduct of fracking) through the membrane, leaving salts and pollutants behind. Because the system can run completely on solar power, it is an ideal fit for fracking wells out in rural plains without access to cheap, centralized power.
“We tested our system with water collected directly from the Gulf of Mexico at Galveston, TX, and about 99 percent of the most abundant ions, such as sodium, calcium, magnesium, and potassium, were successfully removed,” Alabastri said. “Moreover, thanks to the combined action of heating provided by the nanoparticles and water vaporization, we were able to completely remove harmful biological contaminants from water containing different bacterial strains.”
Fracking has continued to rise in popularity within the oil and gas industry, accounting for roughly half of U.S. crude oil production last year and on a clear rise, per the U.S. Energy Information Administration. With that rise in production, fracking operations have consumed massive amounts of water, often in drought-plagued regions like Texas. While they typically inject their wastewater into underground saltwater disposal wells, a technology like SNOWater could encourage them to recycle it and help curb drought conditions.
“Our technology aims at considerably reducing the costs associated with the treatment of flowback and produced water by employing sunlight as a power source for water purification,” Alabastri said. “A portion of the wastewater, instead of being permanently removed from the water cycle, could be thus reused for energy production, for agriculture, or even as drinking supply.”
Naturally, the greatest way to motivate oil and gas operations to utilize water resources in a more sustainable way is to make it economically viable to do so. SNOWater is thought to be a more cost-efficient treatment technology than traditional solutions because it harnesses free power from the sun. With wastewater disposal costs ranging between $1 and $10 per barrel and injection wells requiring significant digging costs, it could make more economic sense for these operations to treat and reuse produced water.
“While now is too early to predict precise costs for large-scale systems, ‘back of the envelope’ calculations show how, by improving our lab-scale device, we may be able to reduce costs by two-thirds,” said Alabastri. “As a result, not only will fewer injection wells have to be dug, but fresh water, instead of being lost, could be available for sale, thus turning a cost into a revenue opportunity.”
As the Rice researchers work to scale up their technology and get it to fracking sites around the country, they are taking opportunities to describe its potential. Recently, they participated in the University Innovation and Entrepreneurship Showcase presented by the Association of American Universities. While there, they described to members of Congress and their staff how their research can solve some of the country’s most pressing problems in economically-viable ways.
“Everyone was very interested in our work and it was great to show how basic science research, spanning from nanophotonics, plasmonics, and nanoscape heat transport could be translated to a tangible application with potential impacts both for industries in the water treatment business and for people lacking access to a clean water supply,” Alabastri said.