A new water desalination technology may prove a savior for the oil and natural gas industries confronting growing concerns about the wastewater that flows to the surface in the months and years after a well is fracked.
In fracking, or hydraulic fracturing, operations 3 million to 5 million gallons of water are injected deep underground, along with sand and a chemical cocktail, to fracture shale rock and extract the embedded natural gas.
Some of that water returns to the surface immediately after the fracturing. The rest comes back over the course of months and years, which a recent study indicates could overwhelm the wastewater treatment infrastructure in the Marcellus Shale formation, which stretches from New York to Virginia.
The new desalination technology is not aimed at the large volumes of water that flow back just after a frack, but could work unattended by a human for months as it treats the really salty water to drinking-water quality, according to engineers working on the system.
The technique “is very much like an engineered version of what nature does in the rain cycle where seawater vaporizes, forms clouds in the atmosphere which condense and come down as rain,” John Lienhard, a mechanical engineer at the Massachusetts Institute of Technology, told NBC News.
“But what we’ve got is clearly a system that’s been designed to optimize performance and to minimize the amount of energy that is required to do the vaporization.”
Water from actual natural gas wells, sent to MIT by the companies that operate them, was run through the system, producing clean, potable water.
The system is a variation of the standard desalination process where salty water is vaporized and then condenses on a cold surface. The salt is separated out in the vaporization.
Lienhard and colleagues use what’s called a carrier gas process where water is sprayed onto warm air to vaporize it. This warm moist air, which carries pure water vapor, is bubbled through cool water where the vapor condenses.
While other researchers have developed so-called humidification dehumidification desalination systems, Lienhard and colleagues maintain that theirs is more energy efficient and comes with the advantages of having simple hardware, low maintenance, and is optimized to process between 1,200 and 2,400 liters a day.
That makes the technology well-suited for desalination in rural coastal villages in developing countries, which the researchers said was the inspiration for their research.
“And it turns out that those are very similar to the requirements that you have in dealing with water that is coming up in the oil and gas wells,” Lienhard said.
Hundreds of natural gas wells are distributed across landscapes such as the Marcellus Shale, the Bakken formation in North Dakota and the Permian Basin of West Texas.
Lienhard said he envisions the desalination plants at each individual well pad, processing hundreds to a few thousand liters of produced water per day at a cost of about “a couple of dollars” per barrel.
The team has filed for patents on the technology and launched a company to commercialize it.
“We hope to have a pilot plant running at a natural gas site within 12 months,” Lienhard said. “If the pilot works, then we could immediately scale it up.”
John Roach is a contributing writer for NBC News. See full article here