Three ways to desalinate water -- RO may not be the best
“We're nowhere near where we can be in terms of energy efficiency and
efficiency of membranes or other kinds of processes to get salt out of
water,” he said. “We've been stuck with reverse osmosis for maybe 30
or 40 years. We've been coasting on this technology and it's time for the
start of a new generation.”
Desalination techniques in use today include: Reverse osmosis, which uses pressure to drive water through a membrane, leaving the salt behind; Thermal methods use heat to distill water while recapturing heat from vapor condensation; and Electrodialysis uses an electrical potential to drive ions through a membrane leaving the water behind.
“Reverse osmosis right now is not particularly energy efficient,” said Bourcier. “It's sort of limited. It's never going to be very energy efficient because it's does the whole process backwards. It removes the water from the salt.”
Bourcier said electrodialysis is better in concept, but still
“It's a technology that uses electrostatic fields to pull ions across membranes, so you're doing the right thing,” he said. “The membranes that are being used in electrodialysis are very resistive. They, again, were invented in the 1950s and no one's done much with them since then.”
Bourcier added that when the national laboratories decided to try and work on the subject of desalinization, three of the labs - Sandia, Livermore and Oak Ridge - all chose to try and improve electrodialysis independently of one another. The three labs have now partnered to try and move the project forward more quickly.
“Then there's the thermal method,” said Bourcier. “Basically
boiling water. You want to boil water and leave the salt behind and that
takes a lot of energy. That's an ancient technology.”
Bourcier and his team are working on a system using nanotechnology that would not only make the electrodialysis process more efficient, but cheaper as well. The membranes in their system would be able to selectively remove only certain elements, such as arsenic and nitrate, while allowing the other elements to remain.
They are set to begin the pilot testing phase of the system and are looking for a location for a full demonstration test. Bourcier said they believed IWV would be a good place for such a full-scale test.
Bourcier was only making a presentation to the board at this time, and
no action was taken during the meeting. Board members did express optimism
that a deal may be reached to bring such a program to the district as a
supplement to existing programs.