Success Story

California Partners with Lawrence Livermore National Lab to Mitigate the Impact of Droughts

LLNL FTECD model

Flow-through electrode capacitive desalination (FTECD) uses hierarchical porous carbon in a device where a stream passes through the electrodes, resulting in saltremoval rate improvements. In this rendering, saltwater enters the carbon aerogel electrodes (left) leaving behind sodium (green dots) and chloride (blue dots) ions. Clean water exits on the right. Photo rendering by: Kwei-Yu Chu

Like much of the western United States, California has experienced the realities and challenges that accompany large-scale severe drought. From 2011 to 2017, California experienced some of the severest drought conditions dating back to the late 1800s. The need to address the state’s susceptibility to drought with cutting-edge water and energy innovations became a priority.

The California Energy Commission (CEC), through its Electric Program Investment Charge (EPIC), supports new energy solutions by fostering regional innovation and bringing clean energy ideas to the marketplace to benefit California’s electric utility ratepayers. EPIC funded an effort by Lawrence Livermore National Laboratory (LLNL) to find a new solution that would reduce the cost of water desalination and increase water reuse.

Using reverse osmosis (RO) technology to desalinate water has been around for decades. However, current methods require an extensive infrastructure, are energy-intensive, and expensive to operate. It requires energy to produce the pressure needed to push the water through the filtering membranes. Can desalination be achieved through a more cost-effective method? LLNL researchers believe they have done just that. They have developed a new capacitive desalination (CD) technique that could ultimately lower the cost and time of desalinating water.

With more traditional capacitive desalination, a voltage is applied between two porous electrodes to adsorb ions onto the electrode surface and thus remove them from the feed stream. Due to the small pore sizes of the electrodes, the feed stream flows between the electrodes and through a dielectric porous separator. However, the new technique, called flow-through electrode capacitive desalination (FTE CD), uses new porous carbon materials with a hierarchical pore structure, which allows saltwater to easily flow through the electrodes themselves. Flowing through an electrode rather than between two electrodes allows for several significant advantages, including faster desalination, more salt removed for each charge of the capacitor, and more energy-efficient desalination.

FTE CD has several advantages over RO. FTE CD requires no membrane components and can operate at low pressures and temperatures; and energy recovery is performed with a solid state circuit, which is more scalable and cost-efficient than the turbines used for energy recovery in RO. FTE CD can also be tuned to remove other targets such as nitrates, calcium, magnesium and more.

LLNL researchers will be demonstrating the FTE CD technology at the Delta Diablo water treatment facility in Antioch, California. The goal is to take tertiary treated water from the plant and remove salt and nutrients so that it can be used in the plant’s cooling tower without requiring extensive chemical treatment.