Nanotechnology Science Could Revolutionize Treatment Practices

The production of minuscule particles and materials through scientific advances, also known as nanotechnology, could be the next greatest innovation to help water and wastewater industry professionals do their jobs.

At the same time, the unknown effects of nanoparticles on the environment pose risks for wastewater plants in particular, given the newness of a fast-growing industry that federal officials have yet to grasp and regulate.

“In my opinion, nanotechnology will break through in the next decade in the water industry. It will help industry to improve water quality and reduce costs,” said Jan Hofman of Kiwa Water Research in Nienwegein, The Netherlands.

Many experts agree with Hofman’s assessment while urging cautious and slow expansion. Because nanomaterials are in some cases new chemicals, they may not react in the same ways as their well-established chemical parents.

A report by the Project on Emerging Nanotechnologies called “EPA and Nanotechnology: Oversight for the 21st Century” notes that this industry has moved quickly from the lab into the marketplace over the past two years. Today, there are more than 450 manufacturer-identified nanotechnology- related products in the commercial market and more than 600 raw materials, intermediate components, and industrial equipment items used by nano manufacturers.

For those in the water and wastewater industries, emerging applications use nanotechnology to improve water and wastewater treatment, prevent water pollution, or clean up tainted water sources.

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A nano primer
By 2014, according to some estimates, 15 percent of all goods manufactured globally will involve nanotechnology. According to one definition from the U.S. National Nanotechnology Initiative, “nanotechnology” is “the understanding and control of matter at dimensions of roughly 1 to 100 nanometers.” A nanometer is a billionth of a meter. To put that in perspective, a human hair is about 60,000 to 120,000 nanometers wide and a red blood cell is 2,000 to 5,000 nanometers wide.

Nanoscale particles are so tiny they must be viewed with super-magnifying scanning tunnel microscopes. In the Project on Emerging Nanotechnologies report, categories of nano materials, processes, and products are as follows:

• Nanoparticles that come from natural processes or that exist in nature, such as sea spray containing nano-size particles and most viruses.

• Nanoparticles that are byproducts of human activities, such as from welding or exhaust from diesel and gasoline-fueled vehicles.

• Nano manufacturing processes used for making nanomaterials. New types of microscopes and ways of handling minute amounts of materials have made it possible to put things together atom by atom.

• Nanomaterials developed to take advantage of the unique properties of nano, such as nanotubes, quantum dots, and nanocrystals.

• Nanoproducts, which are products containing nanomaterials. In early 2007, almost 400 nanoproducts were on the market, including clothing, golf clubs, and milkshakes. Sixty-seven of these products are cosmetics, the largest single category, and 18 are sunscreen preparations.

Improved power
Nanotechnology in the drinking water industry remains in its infancy. Nevertheless, research involving applications in this area has been booming and yielding results that could make its way into the industry in the coming months.

Hofman said adsorptive nanoparticles can be very effective due to their high specific use area and special surface properties. For example, specific (magnetic) iron oxide particles or impregnated carbon nanotubes can be used to remove heavy metals such as arsenic, mercury, cadmium, and chromium. Several of these particles and their applications have been patented.

“Tiny particles that will remove pollutants from the water, in my opinion, many of them [in the future] are going to be based on nanosized magnetite particles,” said Pedro Alvarez, a professor and environmental engineer with Rice University’s Center for Biological and Environmental Nanotechnology.

Alvarez said such particles work through magnetic separation properties to treat water. This technology has been tested in rural groundwater sources to remove arsenic. A powdery substance with nanoparticles is mixed into the water, “sucking up all the contaminants,” he explained.

“It’s a very powerful absorbent for heavy metals that contaminate our waters, particularly arsenic,” Alvarez said. This technology, termed magnetic nanosorbents, was tested in 2006 at groundwater sources in Brownsville, Texas, and in Managua, Nicaragua, by Rice University researchers.

“We’re still tweaking a few things, but I envision this will be very cost-effective to solve some of the world’s problems of arsenic, primarily in developing countries,” he said.

Magnificent membranes
Another important nanotechnology development for water and wastewater industries and groundwater remediation relates to improved membrane strength and performance attributes through use of nanomaterials. Mark Wiesner, a professor of civil and environmental engineering at Duke University, has been researching nanomaterial-enhanced membranes for the past decade.

“We’re making new anti-fouling membranes, reactive membranes, and membranes with improved strength characteristics,” said Wiesner. “We’re making ceramic membranes out of nanoparticle precursors which would replace current methods for making ceramic membranes.”

These ceramic membranes are made out of metal-oxane particles. Iron or aluminum nanoparticles deposit on the membrane surface and are centered to form the ceramic body. An advantage, Wiesner said, is that this type of membrane is environmentally more benign and more stable than ceramic membranes made through the conventional sol-gel process, which involves suspension of particles that can be unstable and finicky to work with.

Wiesner will work with a startup company, Oxane Materials, to market the ceramic membranes constructed through nanotechnology. Hofman said other interesting research in membranes involves a new reverse osmosis membrane for seawater desalination developed by Eric Hoek at the University of California.

“This membrane will reduce the energy consumption for desalination with a factor of 2 and will have improved salt rejection properties. This membrane is now under development for commercial application and has high potential to break through on the market,” she said. Nanoparticles also can be used to change the wettability properties of membranes to prevent fouling, Hofman said. In addition, nanoparticles may be used to detect membrane integrity, which is important to guarantee their safe application in disinfection.

Pollutant eaters and super sensors
Effective tools for water pollution remediation involve reactive nanoparticles that can be used to break down contaminants. Such is the case with reductive particles like zero-valent iron that can be used to treat chlorinated organic compounds like lindane or trichloroethylene (TCE). Hofman said another example involves oxidiative particles, such as titanium dioxide, that can be used in combination with ultraviolet light to oxidize organic micropollutants.

At Rice, researchers have developed a catalyst that destroys difficult-to-remove pollutants such as TCE more than 100 to 1,000 times faster than existing catalysts. This year, that catalyst will be tested at a groundwater site in Texas that’s polluted with chlorinated solvents.

Other nanotechnology applications for the industry involve the combination of biotechnology and nanotechnology (quantum dots) to create powerful sensitive probes that detect specific DNA combinations, added Hofman.

Ready for nano?
Although numerous products and processes involving nanotechnology will help the industry in the coming years, cost is still a prohibitive factor, as is concern regarding regulation and the health effects of these new nanoparticles.

But, said Alvarez, “the cost of production of these nanomaterials is dropping very fast as the volume of production increases.”

While Alvarez forecasts nanotechnologyenhanced membranes will be an effective treatment tool for water and wastewater plants, other nano products would be less practical to use at the plant level.

“It makes more sense to treat it at the point of use,” he said, though how that would play out in reality is unknown at this point. Nanomaterials already are being used to treat pollution and hazardous waste.

Cynthia Finley, director of regulatory affairs for the National Association of Clean Water Agencies, said one concern is the pass-through of nanomaterials in treatment plants to drinking water and wastewater discharges, because little is known about the health effects of some of these tiny particles.

“At this point our treatment technology is not designed [to detect] nanomaterials. If nanomaterials are in our receiving waters, we could eventually be required to remove the nanomaterials from our effluent,” Finley said.

That is why the U.S. Environmental Protection Agency has launched a Nanoscale Materials Stewardship Program aimed at increasing the understanding of this technology and to ensure oversight of nanoscale industrial chemicals. The effort will call on manufacturers of engineered nanoscale chemical materials to report key information to ensure safe use.

J. Clarence Davies, a former EPA official and senior adviser at the Project on Emerging Nanotechnologies, terms the agency’s current oversight “inadequate.”

“It is essential that EPA move quickly to recognize the novel biological and ecological characteristics of nanoscale materials. It can do this only by using the ‘new uses’ provisions of the TSCA (Toxic Substances Control Act),” Davies said in a press statement. “With the approach outlined by EPA and because of the weaknesses in the law, the agency is not even able to identify which substances are nanomaterials, much less determine whether they pose a hazard.”

Despite the unknown environmental risks of nanotechnology, many are convinced the benefits for water and wastewater treatment and pollution remediation outweigh any negative concerns.

This article originally appeared in the 10/01/2007 issue of Environmental Protection.

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