Reclaiming Water from Oil Production

Since the 1990s, governmental regulations on accessing water and disposal limitations have become increasingly stringent. As a result, oil and gas executives are reassessing their current water utilization activities and are working to adopt a longer-range perspective on water life-cycle management. The previous solution –impounding wastewater for evaporation in surface ponds and trucking it over long distances to deep-well injection sites—is not viable in the long term. To respond to these challenges, new treatment technologies are emerging that make it possible to reuse this precious resource. Several systems currently are being developed or in testing and each of them depends on valves to direct and control the process. This article covers a sampling of systems and processes being employed to reduce the impact of hydraulic fracturing on the water supply and the environment.

Electro Water Separation (EWS)

Riggs Eckelberry, CEO of Origin Oil and Bill Charneski, president of the Petro Division at Origin Oil, developer of the EWS system, shared the concept of the system. “The genesis of the technology started in the algae business,” said Eckelberry. “The company was founded in 2007 to find ways of growing algae and harvesting it. Over the years, we developed the process of the most efficient way of dewatering algae. But about a year and a half ago, we found that the process—electro water separation, which is used for algae—worked really well for removing emulsified oils, free oils, suspended solids, anything that wasn’t dissolved in the water.”

“We realized that this could be used for the treatment of produced and frack flow-back water so we began testing the process,” Charneski explained. “A lot of people think just about the frack flow-back water, but that is not the only problem water. Even after the flow-back has stopped, the well is going to produce water with the oil that’s down in the reservoir. There can be about eight barrels of produced water coming out of the ground with one barrel of oil. That ratio can be as low as 3 to 1 or as high as 20 to 1, which means that oil producers are also water producers.”

This process supports a report published by Rice University scientists, Andrew Barron and Samuel Maguire-Boyle; they recommended chemical treatment of fracking wastewater be kept to a minimum. The scientists pointed out that many standard treatment methods use halogen-containing oxidants to remove bacteria from the water. However, these oxidants also react with naturally occurring hydrocarbons, forming environmentally detrimental chlorocarbons and organobromides. Therefore, they say, treating the water chemically may not be the best solution.

Continuing with the EWS process: From the oil knockout tank, the oil and water is sent to the first step, electro coagulation (EC), where the oil and water emulsion is broken. There the natural charge on the oil droplets and the suspended solids is removed so that they will coalesce. The electro coagulation takes those 1 to 25 micron-sized droplets and particles and causes them to become larger, above 25 microns, where they can actually be separated by flotation. The water then flows out of the EC cell into the flotation chamber to the second step. There, micron-sized gases are generated. They attach themselves to the eglomerated solids and oil particles and lift them to the surface of the water. As the water goes through the four-chamber flotation tank, it gets increasingly purer, and as it exits the flotation chamber, it is on the order of about 95% pure water. The sludge, oil and solids go into a sludge chamber and gets pumped back to the oil knockout tank. That product can then get pumped back to the knockout tank and go through the cycle again.

Together, these stages also accomplish the important third function of electro-oxidation, which is effective in removing bacteria, as well as certain ions that are capable of being precipitated from the finished water.

“The water then goes to the polishing stage where the total hydrocarbon is removed to below the detection levels of total petroleum hydrocarbon (TPH) test,” explained Charneski. “The testing is done by outside labs and results show that the total TPH is below the limits of the test. The same occurs with the suspended solids. The test—called total suspended solids (TSS)—and water produced from this system shows TSS also below detection limits. And there is no waste stream from our process.”

From there, the water can go to the next step, for processes like reverse osmosis, where all the salts are removed, a necessary step for the water to be used for agriculture. “Our process removes all the contaminants so that RO units don’t foul,” Charneski said. “It allows them to do their job.”

“The valves are a critical part of any process,” stressed Charneski. “In our system, we use of course on/off valves as well as control valves for levels and flow rates. They are integrated and an essential part of the process, and they are all automated. The process is controlled with a PLC.”

The EWS system is in its early stages of commercialization, but has had successful testing in a system with gas wells in Colorado and West Texas intermediate oil fields and is currently in testing in oil fields near Bakersfield, CA.

Integrated Treatment System (ITS)

The ITS platform was created by Ecologix. It is mobile and set up in three trailers at the site, using the dissolved air flotation (DAF) process, a system commonly used for separating solids, fats, oil, and grease from a waste stream. Each of the trailers holds one of the three main units in the system: the first controls chemical dosing, the second mixes the chemicals into the water, and the third performs the physical separation of solids from the water. During the third step, pressurized water is saturated with dissolved air and is discharged into a flotation vessel. The microscopic air bubbles attach to solids and float them to the surface, forming a sludge blanket. A scraping assembly skims the sludge off the surface of the water and into a sump. From the sump, sludge is pumped to dewatering equipment. The treated water flows from the DAF vessel for discharge or on to other treatment processes. The ITS can process 900gpm (31,000bbl/day) of produced water.

Microbial Capacitive Desalination (MCD)

While it is still in the research stage, MCD holds promise to treat produced water. Microbial desalination cells (MDCs) use the electrical current generated by microbes to simultaneously treat wastewater, desalinate water and produce bioenergy.

A recent study in which MCD was used to treat actual shale gas produced water showed that it was possible to treat the water with no external energy input. Biodegradation of the organics generated stable voltages for desalination while dissolved solids were also removed in the reactor.

As with any system, valves are necessary to direct and control the flow of the produced water into the system, to direct it within the system, and to divert the clean water to its final destination outside the system.

Centralized Water Management

While these and many other on-site processes hold promise, many in the industry believe that what is really needed is a more unified approach to treating water from oil and gas production. Some believe that the main problem with mobile wellhead solutions is that they cannot continuously process the ongoing produced wastewaters, which could require handling for 20 years following fracking.

Thus, the idea of a centralized wastewater management concept is gaining momentum. There are more than a dozen such wastewater treatment facilities either in development or currently serving shale oil and gas drilling in North America. These facilities can handle both the flow-back wastewater and produced wastewater from oil and gas wells within a region, at a radius of 40 to 50 miles. Pipelines connect all wellheads directly with the central treatment plant.

The concept of these centralized plants is just now becoming accepted, but it is increasingly apparent that the development of an integrated infrastructure for water management in this industry has lagged behind advances in drilling technology. This is definitely an area in which the valve industry can be actively involved and assist producers to effectively manage their operations while protecting critical water supplies.

Kate Kunkel is senior editor of VALVE Magazine. Reach her at kkunkel@vma.org.