Engineered nanomaterials (ENMs) are increasingly being used in commercial and industrial applications. Yet a new study shows that current methods of water treatment are not sufficient to remove them.

Four researchers from the University of California, Riverside, analyzed the ability of typical water pretreatment methods to remove titanium dioxide (TiO2), the most commonly used ENM. Nichola Kinsinger, Ryan Honda, Valerie Keene and Sharon Walker conducted scaled-down tests designed to evaluate the effectiveness of three traditional methods of prefiltration treatment in which particles may be removed: coagulation, flocculation and sedimentation.

Results pointed to the possibility for significant release. Around 5 ppm of particles smaller than 450 nm were observed after sedimentation, raising concern over the ability of treatment facilities to adequately remove these nanoparticles, which are increasing in production and use, the authors said.

Previous studies have found that TiO2 nanoparticles can potentially cause adverse environmental effects and may be harmful to health.

"While further optimization of such treatment processes may allow for improved removal efficiencies, this study illustrates the challenges that we must be prepared to face with the emergence of new engineered nanomaterials," commented Sharon Walker, Professor of Chemical and Environmental Engineering at the University of California, Riverside.

The results are detailed in an article published in Environmental Engineering Science, the official journal of the Association of Environmental Engineering and Science Professors.