Key Takeaways
- Approximately 40 percent of the U.S. water supply comes from underground aquifers but much of it is too salty for many human uses.
- By sufficiently treating brackish groundwater to separate salts and other contaminants, the U.S. could significantly expand its supply of freshwater.
- A new technology, developed by the California company Active Membranes with funding from the National Alliance for Water Innovation led by Berkeley Lab, equips membranes used in the reverse-osmosis desalination process with electrical conductivity. This improves the membrane's ability to separate salts and other contaminants from hard-to-treat waters such as brackish groundwaters and the wastewater that is brought to the surface during oil and gas extraction.
Approximately 40 percent of the U.S. water supply comes from underground water reserves, but far more brackish groundwater is available–much of it too salty from calcium and magnesium content, however, for practical use. In fact, the amount of brackish groundwater in the U.S. is more than 800 times the amount of fresh groundwater pumped from all other sources every year, according to U.S. Geological Survey estimates. By sufficiently treating brackish groundwater to separate salts and other contaminants, the U.S. could significantly expand its available water supply.
A new technology equips membranes used in the reverse-osmosis desalination process with electrical conductivity, improving their ability to separate salts and other contaminants from hard-to-treat waters. Active Membranes, a California-based company, licensed the technology originating from UC Riverside and UCLA to advance its development and bring it to market. Their team received funding for this work from the National Alliance for Water Innovation (NAWI), a public-private partnership led by the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab). NAWI focuses on advancing technologies that enable the use of unconventional water sources in real-world settings. In addition to federal support, NAWI is backed by several California water agencies, reflecting strong regional interest in securing reliable water supplies.
According to NAWI Executive Director Peter Fiske, the new active membrane can effectively treat wastewater that is brought to the surface during oil and gas extraction. This "produced water" is loaded with salts, particles, and hydrocarbons, all of which contribute to rapid scaling and fouling of conventional membranes.
"In a normal oil well, there is far more produced water than oil, and the disposal of this water often limits oil and gas production. Treating and desalinating produced water could allow this 'wastewater' to become a source of irrigation for agriculture," said Fiske.
"Treating and desalinating produced water could allow this 'wastewater' to become a source of irrigation for agriculture."
— Peter Fiske
A widely used method to remove dissolved salts and other contaminants from water is reverse osmosis (RO). RO uses ultra-thin membranes that enable water under pressure to pass through the membrane while blocking salt and other contaminants. A common problem with membrane-based water purification is the build-up of salts and organic matter on the membrane-two phenomena that are called "scaling" and "fouling," respectively. To avoid scaling, RO membranes must be frequently backwashed and cleaned, which raises costs and reduces water production.
Active Membranes has developed a novel approach to keep membranes clean. By applying an ultra-thin, electrically conductive coating on top of the membrane and then charging the surface with low voltage, the salt ions and other charged species in the water are pushed away from the membrane surface, reducing scaling and fouling. In a recent field pilot in Ventura County, which tested the electrically "active" membranes against conventional membranes, the active membranes demonstrated a 20-30% improvement in water production.
"I think the next big step we take to get the desalination field where it needs to be in terms of footprint, cost, and sustainability has to involve looking at the membrane separation process," said Arian Edalat, co-founder and CEO of Active Membranes. "Our approach gives the membrane the power to keep itself clean."
NAWI is a team of academic and industry partners, supported by investment from the Department of Energy and expertise from DOE's national laboratories. Additional funding for NAWI comes from several California water agencies, including the California Department of Water Resources and State Water Resources Control Board, and the California Energy Commission. NAWI supports a portfolio of research projects, like Active Membranes, that work to strengthen desalination technologies.
NAWI's goal is to advance technologies that radically reduce the cost and energy required to make nontraditional water sources suitable for reuse in energy applications, or as sources of potable water. Over the past five years, NAWI has supported a robust research portfolio with 67 original and innovative research and development projects that span analysis for water-energy grid integration to the development of algorithms, models, and adaptive process controls for resilient operations. NAWI has also supported the implementation of 15 pilot projects that have begun work demonstrating some of these innovative technologies in real-world environments.
"Piloting in realistic operating environments is a critical step in validating a new water-treatment technology. Laboratory environments and simulated water chemistries can only take you so far. At some point the acid test is: can this system make clean water from a complex source of water in a realistic environment," Fiske said.
NAWI is led by DOE's Lawrence Berkeley National Laboratory in collaboration with National Energy Technology Laboratory, National Renewable Energy Laboratory, Oak Ridge National Laboratory, and SLAC National Accelerator Laboratory, and is funded by the U.S. Department of Energy with additional support from the California Department of Water Resources and the State Water Resources Control Boards.
