New Membrane Technology Could Expand Access to Water for Agricultural and Industrial Use

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.