Purification at the Nano Scale

January 25, 2014 — Leave a comment

Recent events in Japan have sparked concerns about freshwater availability in many parts of the country. Fortunately for Japan, the nation is also the world’s leader in water filtration.

Japanese manufacturer Nitto Denko is currently marketing what it claims is the world’s most efficient desalination filter, the SWC6 MAX, a reverse-osmosis nanomembrane system released in 2010. According to the company, the filter can remove “salt and other minerals as well as bacteria and viruses from seawater, and lower the 3.5% of salt in seawater to 0.0075%”-lower than the salt content of freshwater. The SWC6 MAX was invented by Hisao Hachisuka and is currently in use in a water treatment facility in Australia.

At present, SWC6 MAX water is rather expensive. The cost of filtering an acre foot is more than $650, because of the amount of energy required to push water through the filter. That price tag is beyond the means for the world’s poorest inhabitants but within reach for the Japanese. The company has not said that it will be using the technology in the areas affected by the March 2011 tsunami or radiation. However, numerous other technologies exist for effective wastewater filtration, which could be used in Japan, including ozone injection and nanofiltration.

One of the more interesting water purification technologies to emerge recently is electro-filtration through silver nanowire fiber. The silver nanowire mesh, connected to a 20-volt power source, zaps bacteria and pathogens, making the water drinkable. This method, pioneered by Stanford University professor Yi Cui, has been shown to be more effective and less energy- intensive than other filtration methods that require large amounts of energy to push water through filters.

At present, silver nanowire filtration is also cost-prohibitive for the world’s poorest regions, due to the high cost of constructing silver nanowires. But in 2010, Taiwanese chemist Yi-Hsiuan Yu patented a process for mass production of silver nanowires. If this method is effective, it could greatly reduce the cost of production for these nanowires, making Yi Cui’s filter more practical for the world’s poor. Korean firm Toptec has patented the world’s first nanofiber mass production system.

The Global Water Recycling and Reuse System Association of Japan has a large, government-funded mandate to “develop [a] comprehensive water recycle system and expand the system, making the most use of Japanese technologies and knowhow.” The Japanese government sees water filtration and green infrastructure as a key export area for the future.

The United Nations estimates that 2.8 billion people will live in a water-stressed environment by 2025. The world’s poorest people need access to cutting-edge desalination technologies, coupled with advanced filtration, to increase the availability of freshwater and to remove toxins from wastewater. Wastewater recycling on the community level is essential for water stability, many experts contend. According to the Japanese government, there will be a $1 trillion market for safe water reclamation and recycling by 2025, so the potential private client list is considerable.

-Patrick Tucker


Stanford University professor Yi Cui is the creator of a silver nanofiber that may make water purification on the nano scale less expensive.


Sources: Nitto Denko Corporation, http://www.nitto.com. Stanford University, http://stanford.edu. Personal interviews.

Originally published in THE FUTURIST, July-August 2011


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