New Desalination Membrane May Reduce Costs For Drinkable Ocean Water
If you happen to live in Southern California, close to the Pacific Ocean, you probably often wonder why your water district limits you to 10 minute yard-watering three times per week, when it hasn't rained in 38 weeks... Why, every fall, are wild fires destroying hundreds of homes and thousands of acres of land and wildlife... Why do you have to depend on water that flows down from Colorado through Arizona for your entire water supply, and it's only barely enough if Colorado had a lot of snow the prior winter?
Southern Californians are told over and over again that desalination is extremely costly and that no one wants to pay for it, but we still wonder how we can sit right on the coast of the largest body of water on the planet and not focus all of our human intelligence on getting usable, affordable water from the sea.
Is it too early to say, 'Greetings Pilgrim, your search has ended?' I don't know, but the new desalination membranes developed by researchers at the University of California at Los Angeles (UCLA) Henry Samueli School of Engineering and Applied Science sure look like a huge step forward in making ocean water healthy for human use and consumption throughout the world.
Normally, reverse-osmosis desalination uses high pressure to force polluted water through a membrane, causing the membrane to get clogged with minerals, bacteria, and other impurities that were prevented from passing through. As a result, the membranes need to be cleaned or replaced often; if not, the pumping system will eventually break down. This is one expensive clean-up.
But the UCLA membrane is made of a polyamide thin film composite that is activated by atmospheric-pressure plasma, rather than high pressure. The plasma creates active sites on the new membrane where reactions are initiated that create a 'brush layer' on the polyamide surface. Because the brush layer is constantly moving, it makes it nearly impossible for impurities to stick to it.
Another aspect of the membrane is that the chemistry of the brush layer can be chosen to repel molecules of an opposite charge, making the membrane extremely adaptable to different water environments.
Nancy H. Lin, a UCLA Engineering senior researcher and the study's lead author, indicated that "The cost of desalination will therefore decrease when we reduce the cost of chemicals [used for membrane cleaning], as well as process operation [for membrane replacement]. Desalination can become more economical and used as a viable alternate water resource."
The engineering team is working with the UCLA Water Technology Research Center (WaTeR) to test the new membrane under field conditions.
The new desalination method, described in detail in the Journal of Materials Chemistry, offers hope for greater access to consumable water in the future. It, and further developments like it, are very welcome innovations.