Nanonoparticles forced to clump won't flow into the environment

Nanoparticles in municipal sewage treatment plants — their main gateway into the environment — may be redirected by a new detergent-coating technology.

Two million tons of nanoparticles, only 1/1000th the width of a human hair, are used by manufacturers each year in foods, cosmetics, medicines, and other consumer products. The most conservative scientific studies have indicated that some nanoparticles, tiny enough to slip by sewage treatment processing, have already damaged the environment. While the environmental impact of the emerging nanotechnology industry is being studied further, the production of nanoparticles is increasing rapidly. Helen Jarvie and her colleagues from the UK Centre for Ecology and Hydrology are focusing on the behavior of nanoparticles in wastewater to find a way to trap them before they flow into aquatic environments. The team used neutron scattering (at the UK's ISIS Facility) to view the sewage at the nano scale because nanoparticles are too small to be visualized optically. In this method, neutrons penetrate the sewage "soup" and are tracked as they scatter strongly from flowing or aggregating nanoparticles. The study showed that coating silica nanoparticles (similar to those used in ointments, toothpaste and household cleaners) with a detergent-like chemical caused the nanoparticles to clump together into sewage sludge, a material that is is often stored in landfills or recycled into agricultural fertilizer. Uncoated nanoparticles stayed in the water and were released in the effluent stream. The team's study has been published online November 12 in the American Chemical Society's journal, Environmental Science & Technology.