Altough the use of nanoparticles have become a symbol of modern technology, they actually have a long history and were for instance utilized by 9th century Mesopotamian artisans to create a shimmering effect on pots. Today, nanoparticles are a popular addition to products such as food and cosmetics and one million tonnes of silica nanoparticles alone are used by manufacturers each year. A large proportion of these enter the sewage system, but at present we hardly know anything about what happens to them during sewage treatment or their potential effects on the environment once the treated waste water is released into the wild.

It is therefore exciting to hear that a new technique has been developed that may help remove nanoparticles from sewage – or at least the silica ones. If you coat silica nanoparticles in surfactants (detergent-like chemicals that lower the surface tension of a liquid) they clump together and can easily be removed during primary wastewater treatment. Coated nanoparticles interact with other sewage components, forming a solid sludge.

The discovery is the result of the collaborative efforts of scientists from the Centre for Ecology & Hydrology, ISIS Neutron Source, King’s College London and Oxford University.

The research shows that the surface chemistry of nanoparticles influences their likely removal during primary sewage treatment,” says Dr Helen Jarvie of Centre for Ecology & Hydrology, who took part in the study. “By adding a coating which modifies their surface chemistry, it may be possible to re-route their journey through sewage treatment plants, preventing them from eventually entering the aquatic environment.’

More research is now needed to find out if the technique will work on non-silica nanoparticles.

The research paper has been published in the journal Environmental Science and Technology.

The work was funded under the Environmental Nanoscience Initiative (ENI), a programme to investigate the potential environmental effects of nanotechnology. The ENI is a partnership between the Department for the Environment, Farming and Rural Affairs (Defra) Environment Agency, the US Environmental Protection Agency, the Engineering and Physical Sciences Research Council and the Natural Environment Research Council.