Oil and gas operations in the United States produce about 21 billion barrels of wastewater per year. The saltiness of the water and the organic contaminants it contains have traditionally made treatment difficult and expensive.
Engineers at the University of Colorado Boulder have invented a simpler process that can simultaneously remove both salts and organic contaminants from the wastewater, all while producing additional energy. The new technique, which relies on a microbe-powered battery, was recently published in the journal Environmental Science Water Research & Technology as the cover story.
鈥淭he beauty of the technology is that it tackles two different problems in one single system,鈥� said Zhiyong Jason Ren, a CU-Boulder associate professor of environmental and sustainability engineering and senior author of the paper. 鈥淭he problems become mutually beneficial in our system鈥攖hey complement each other鈥攁nd the process produces energy rather than just consumes it.鈥�
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The new treatment technology, called microbial capacitive desalination, is like a battery in its basic form, said Casey Forrestal, a CU-Boulder postdoctoral researcher who is the lead author of the paper and working to commercialize the technology. 鈥淚nstead of the traditional battery, which uses chemicals to generate the electrical current, we use microbes to generate an electrical current that can then be used for desalination.鈥�
This microbial electrochemical approach takes advantage of the fact that the contaminants found in the wastewater contain energy-rich hydrocarbons, the same compounds that make up oil and natural gas. The microbes used in the treatment process eat the hydrocarbons and release their embedded energy. The energy is then used to create a positively charged electrode on one side of the cell and a negatively charged electrode on the other, essentially setting up a battery.
Because salt dissolves into positively and negatively charged ions in water, the cell is then able to remove the salt in the wastewater by attracting the charged ions onto the high-surface-area electrodes, where they adhere.
Not only does the system allow the salt to be removed from the wastewater, but it also creates additional energy that could be used on site to run equipment, the researchers said.
鈥淩ight now oil and gas companies have to spend energy to treat the wastewater,鈥� Ren said. 鈥淲e are able to treat it without energy consumption; rather we extract energy out of it.鈥�
Some oil and gas wastewater is currently being treated and reused in the field, but that treatment process typically requires multiple steps鈥攕ometimes up to a dozen鈥攁nd an input of energy that may come from diesel generators.
Because of the difficulty and expense, wastewater is often disposed of by injecting it deep underground. The need to dispose of wastewater has increased in recent years as the practice of hydraulic fracturing, or 鈥渇racking,鈥� has boomed. Fracking refers to the process of injecting a slurry of water, sand and chemicals into wells to increase the amount of oil and natural gas produced by the well.
Injection wells that handle wastewater from fracking operations can cause earthquakes in the region, according to past research by CU-Boulder scientists and others.
The demand for water for fracking operations also has caused concern among people worried about scarce water resources, especially in arid regions of the country. Finding water to buy for fracking operations in the West, for example, has become increasingly challenging and expensive for oil and gas companies.
Ren and Forrestal鈥檚 microbial capacitive desalination cell offers the possibility that water could be more economically treated on site and reused for fracking.
To try to turn the technology into a commercial reality, Ren and Forrestal have co-founded a startup company called BioElectric Inc. In order to determine if the technology offers a viable solution for oil and gas companies, the pair first has to show they can scale up the work they鈥檝e been doing in the lab to a size that would be useful in the field.
The cost to scale up the technology also needs to be competitive with what oil and gas companies are paying now to buy water to use for fracking, Forrestal said. There also is some movement in state legislatures to require oil and gas companies to reuse wastewater, which could make BioElectric鈥檚 product more appealing even at a higher price, the researchers said.
Ren and Forrestal have received funds from the National Science Foundation to work on scaling up the water treatment cell. The grant came after the pair participated in NSF鈥檚 Innovation Corps Program鈥攁imed at pushing NSF-funded research beyond the lab鈥攁nd took first place in their class.
Ren and Forrestal also worked with researchers Zachary Stoll and Pei Xu at New Mexico State University. Stoll and Xu are also co-authors of the article.
The study can be found at .
Contact:
Zhiyong Jason Ren, 303-492-4137
Jason.Ren@colorado.edu
Casey Forrestal
Casey.Forrestal@colorado.edu
Laura Snider, CU-Boulder media relations, 303-735-0528
Laura.Snider@colorado.edu
