A treatment process developed by engineers at the University of Colorado Boulder promises a simpler and more economical way to clean up the wastewater produced by oil and gas operations that is heavily salinated and full of organic contaminants. The technique, which involves the use of a microbe-powered battery, also produces rather than consumes energy.

Just like oil and natural gas, the contaminants in the wastewater produced in gathering these materials contains energy-rich hydrocarbons. Through the consumption of the contaminants, microbes are used to release the energy embedded in these contaminants, generating an electrical current that is used to power the desalination process.

The energy produced by the microbes is used to create a battery, with a positively charged electrode on one side of the cell, and a negatively charged electrode on the other. Since salt dissolves into positively and negatively charged ions in water, which are attracted to and adhere to the respective electrodes, it is possible to remove the salt from the wastewater in what the researchers call microbial capacitive desalination.

"The beauty of the technology is that it tackles two different problems in one single system," says Zhiyong Jason Ren, a CU-Boulder associate professor of environmental and sustainability engineering. "The problems become mutually beneficial in our system – they complement each other –and the process produces energy rather than just consumes it."

Furthermore, the microbes produce more energy than is required for the desalination process, providing the potential for the excess energy produced through the technique to be used to run equipment on site.

"Right now oil and gas companies have to spend energy to treat the wastewater," Ren adds. "We are able to treat it without energy consumption; rather we extract energy out of it."

The technique also offers benefits for fracking, or hydraulic fracturing, which involves injecting water, sand and chemicals into oil and gas wells to increase their production. The scientists say that despite safety concerns, such as earthquakes caused by the wells, fracking operations have increased to the point where there are worries over their use of scarce water resources. The scientists say that their process would allow wastewater to be treated on site more economically and reused for fracking.

Ren and Casey Forrestal, a CU-Boulder postdoctoral researcher, have co-founded a startup company called BioElectric Inc. with the goal of commercializing the technology. But first they will need to prove that it will scale up and show that it is cost effective compared with what companies are currently paying for water to use for fracking. Some state governments may also give the company a helping hand even if their technology ultimately turns out to be more expensive, with moves by some state legislatures to force gas and oil companies to reuse wastewater.

The research was published in journal Environmental Science Water Research & Technology