The news is full of drought stories this autumn. States are fighting legal battles to claim federal water resources. Scientists are predicting that changes to our climate may leave much of the U.S. with multiyear drought for decades to come.
The drought plunging Georgia into a state of emergency this fall set me thinking. How ironic that even states that enjoy miles of coastline are rationing water, truly a case of “water, water everywhere, nor any drop to drink.” Could nanotechnology ease the threat of drought by helping to make our ocean water potable?
The challenge is that the desalinization process that removes salt from salt water is prohibitively costly. In researching this column, I discovered that a few nanotech companies are working to reduce the cost of desalinization to the point where making ocean water drinkable and available for industrial uses can become affordable.
NanoH2O, for example, is developing a membrane containing hydrophilic nanoparticles (that is, particles that attract water) to reduce the electric power required to run desalinization plants. The company employs a process called reverse osmosis, one of the most prevalent desalinization processes in use today. In this process, water molecules are forced through a membrane, separating the water from the salt. Using conventional membranes, high pressure is needed to force the molecules through the membranes. Hydrophilic nanoparticles enable water molecules to pass more easily through the membrane, lowering the amount of pressure required to separate the water from the salt. Lower pressure means lower consumption of electric power at desalinization plants, resulting in significant savings, even when you factor in the additional cost of the nanoparticle enhanced membranes.
Researchers in Australian universities, such as Victoria University, are trying a similar approach. They are working on developing a membrane containing nanotubes. Water would flow inside the nanotubes from one side of the membrane to the other with less pressure required.
CDT Systems is working with a substance called carbon aerogel. Carbon aerogel, developed by the Lawrence Livermore Laboratory, is formed from carbon nanofibers. The surface of electrodes formed from carbon aerogel contains pores less than two nanometers in diameter. It turns out that passing salt water between two carbon aerogel electrodes that have a 1 to 2 volt difference between them removes the salt. The power requirements are low enough that mobile units may even be able to operate on solar or wind generated electricity alone. CDT is planning to start volume manufacturing of water purification systems in 2008.
Let’s hope that these efforts result in lowering the cost of desalinization to the point that cities near the coast are freed from dependence on rain and snow runoff for their water. There would, of course, be capital costs involved in building the desalinization plants and adapting the water distribution system to a new source. However situations like the current drought in the Southeastern and Southwestern U.S. (and the lost revenue from shutting down manufacturing plants that depend upon water to run their manufacturing processes) may convince some states to make the investment. Once coastal cities put this infrastructure in place, inland cities may be able to share the benefits by using aqueducts and pumping stations, such as the system that brings water over mountains to Los Angeles.
In the meantime, if you live in a drought state, you’ll have to watch your grass turn brown and dream of the greener days that nanotechnology might help provide.
To learn more about how nanotechnology can improve water quality visit my Water and Nanotechnology page.