Published on March 7, 2014
Nanoparticles It’ll All Come Out in the Wash…?
Background Info A “nanoparticle” is generally accepted to be between 1 and 100 nanometers (nm) in diameter. For reference, a human hair is about 75,000 nm in diameter. Nanoparticles have been used by humans for centuries, but modern science is responsible for uncovering a multitude of new uses for nanoparticles in medicine, clothing, and other industries.
(Nanoparticle) Some products that use nanoparticles: -stain-resistant khakis -some sunscreens -odor-trapping socks -scratchproof eyeglasses -crack-resistant paints Nanotechnology has caused concern in the scientific community because some believe that not enough research is being done on possible dangers of the particles (toxicity, environmental impact, etc.)
One particular NP that could pose a problem for wastewater treatment facilities is silver (Ag), which is found in (among other things) odor-resistant socks and some new washing machines. Testing has proven that the socks lose NP content over time. Some brands released almost all of their silver content after only 4 washings. (Organism) *cough *Note: Individual socks were tested and found to have as much as 31 mg of silver per sock Some research indicates that Ag NPs, Ag+ ions, and AgCl colloids all significantly inhibit microbial growth and respiration of autotrophic nitrifying organisms.
Ag+ ions inhibit function by attaching to the negatively charged wall of bacterial cells, deactivating cellular enzymes, disrupting membrane permeability, and ultimately leading to cell lysis and death. (Ag+ ions) (Bacteria Cell) Nanosilver particles also pose a threat. They have the ability to pass straight through cell membranes and can lead to cell malfunction. In addition, they are highly catalytic and can generate reactive oxygen species.
Other NPs to Look For Aluminum Oxide NPs, commonly found in sunscreen, can stunt root growth in plants (in very high concentrations, >2 mg/ml water) Titanium dioxide NPs, found in some types of toothpaste, cheese, plastic, chocolate and other products have already been discovered in wastewater biosolids in states across the U.S.
The Good News or “The Silver NP Lining” Nanotechnology has the potential to greatly aid and improve the wastewater industry! Nanotechnology is already being used to detect or remove some of the following materials from wastewater: Cadmium, copper, lead, mercury, nickel, zinc, nutrients (e.g. Phosphate, ammonia, nitrate and nitrite), cyanide, organics, algae (e.g. cyanobacterial toxins), viruses, bacteria, parasites and antibiotics.
Some iron and aluminum NPs are being used to create more benign and more stable ceramic membranes for water desalination. The NP membranes decrease energy consumption for desalination and improve salt rejection properties. Silicon dioxide NPs, currently used in antifogging coatings and potentially as DNA carriers, actually promoted root growth in plants.
Regulations & Monitoring The EPA has spent millions of dollars researching the positive and negative effects of nanoparticles on the environment, but regulations are still few and far between. There is additional debate on whether or not to consider NPs such as silver as “pesticides”, since they are now used to kill pests (bacteria). As of 2007, the EPA does claim silver NPs to be pesticides, which requires their regulation under the Federal insecticide, fungicide and rodenticide act (FIFRA). As of 2006, companies that make products containing silver NPs for the purpose of killing bacteria are required by the EPA to prove that they pose no environmental health risk. However, testing methods are only in developmental stages. As of June 2008, the EPA does not require wastewater treatment facilities to treat nanomaterials.
WERF’s Contributions The 2006 Paul L. Busch award was given to Dr. Paul Westerhoff of Arizona State University, to continue his team’s research on the fate of commercial nanomaterials in drinking water and wastewater treatment plants, and their potential human toxicity. WERF is also funding Dr. Zhiquang Hu of the University of Missouri to research the impact of silver nanoparticles on wastewater treatment. (Both of these projects and their preliminary findings and results were referenced in the preparation this presentation)
Discussion: Strategies or plans of action for wastewater treatment plants to prepare for possible issues with NPs in the near future
Sources: Okkyoung Choia, Kathy Kanjun Dengb, Nam-Jung Kimc, Louis Ross Jr.d, Rao Y. Surampallie, Zhiqiang Hu. The inhibitory effects of silver nanoparticles, silver ions, and silver chloride colloids on microbial growth. Water Research, Vol. 42, 2008. pp. 3066-3074. Dhermendra K. Tiwari, J. Behari and Prasenjit Sen. Application of Nanoparticles in Waste Water Treatment. World Applies Sciences Journal, Vol. 3, 2008. pp. 417-433. Anonymous. Nanoparticle Impact on Plants. United Press International, 2005. Physorg.com Melissa Crytzer Fry. Too small to see: the environmental impact of nanoparticles. Arizona State University, 2008. Summer Intern, Holland BPW Made by:Reyno Andrew
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