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SPIE Professional October 2009

Photonics for a Better World: Clean Water

SPIE Professional highlights some of the optical technologies that bring tangible social, environmental, health, and economic gains to humanity.

By Beth Kelley

A UV system fromCalgon Carbon
UV Disinfects Water

Long exposure to UV wavelengths is unsafe for living organisms, but it's great for treating water. Ultraviolet radiation of wastewater has been used for a number of years in Europe, the Middle East, and China, and all drinking water in St. Petersburg (Russia) has been disinfected with UV since December 2007.

With new environmental rules set to take effect in the United States in 2012, several U.S. cities are adopting UV treatment systems as a safe, effective water treatment strategy.

The new Environmental Protection Agency requirements demand at least two types of disinfectant or filtration systems for all municipal-provided water by April 2012, says Enio Sebastiani of the San Francisco Public Utilities Commission.

Most cities already have filtration systems or chemical treatment plants which add chlorine to the water. UV treatment plants are considered a good option not only for their effectiveness, but because they are affordable to install and do not introduce anything new into the water.

UV water treatment works by pumping water into a reactor with UV lamps that can produce 40 millijoules per square centimeter of short-wave and mid-wave UV light (between 200-300 nanometers). These wavelengths are germicidal, deactivating about 99% of organisms like Cryptosporidium and Giardia, which are typically resistant to chlorine. The lamps themselves are low-energy.

The first and largest U.S. water treatment plant to employ UV technology, the Seattle Cedar Water Treatment Facility began operating in 2004. It treats 180 million gallons of water per day. "We used to just chlorinate" the city water, says Alex Chen, Seattle Public Utilities senior water quality engineer. "Now in addition, we oxidate and radiate the water."

Brian Altland, UV product manager at Calgon Carbon Corp., explains that when hydrogen peroxide is added, the UV creates OH radicals which oxidize compounds in the water, including contaminants.

Calgon Carbon is supplying 12 UV reactors to the city of San Francisco for its Tesla Portal Treatment facility, now under construction. When completed, it will be the largest in California, treating up to 320 million gallons of drinking water per day. Lawrence Livermore National Labs is also installing UV treatment systems for its water supply.

New York City is constructing the Catskill/Delaware UV Disinfection Facility, and it will be the largest UV treatment plant in the world, supplying over 90% of the city's drinking water. Expected to begin operating in 2012, the facility will use 56 low-pressure, high-output UV reactors to treat some 1.3 billion gallons of water daily.

Calgon UV filtration system
A Calgon UV system. Photo courtesy of Calgon Carbon Corp.
Satellites Sense Disease, Pollution

EDEN, a group of laboratories and public-health agencies in 24 European and African countries, is using satellite data to foresee when and where epidemics will strike next so that appropriate countermeasures can be taken.

David Rogers, an expert in ecology and disease at Oxford University, for instance, has linked satellite data on photosynthesis to the health and size of tsetse flies to suggest the likelihood of sleeping sickness striking in Africa.

Similarly, researchers at NASA's Goddard Space Flight Center studying climate data from satellites warned authorities in Africa in 2007 of a warming trend in the Indian Ocean that was similar to one in 1997 leading to a devastating outbreak of Rift Valley fever. Preventive measures kept the number of deaths in Africa to 50% less than would have probably occurred.

Space and ground-based optical technologies are also being used to reduce air pollution, determine levels of aid needed after natural disasters or other humanitarian crises, and save money.

Two German inventors won a 2008 innovation prize for devising a system for optimizing unused freight space in lorries and containers. Mario Neugebauer and Jürgen Anke of ubigrate GmbH use GPS tracking data and ultrasonic sensors inside trucks and containers to increase the efficiency of shipping transport and thereby reduce carbon dioxide emissions and shipping costs.

Better Health Through Optics
  • University of Texas at Austin and Stanford University (USA) engineers have patented a laser microscalpel for surgeons to operate on tissue one cell at a time, precisely targeting cancer, epilepsy, and other diseases while leaving healthy surrounding cells alive.

  • Two University of Arizona (USA) researchers have received a $2.4 million grant to design, build, and evaluate two versions of an ovarian cancer medical imaging and screening instrument that uses holographic components in a new type of optical microscope.

  • Aculight Inc. of Bothell, WA (USA), is developing an optical neural technique for mitigating hearing loss among soldiers. The technique involves laser nerve stimulation.

Beth Kelley is an SPIE editor. 

Have a question or comment about this article? Write to us at spieprofessional@spie.org

DOI: 10.1117/2.4200910.05

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