Source: European Commission
Silver nanoparticles’ antibacterial properties mean that they are widely used in a range of materials and consumer products, including plastics, textiles, surface coatings on buildings and cosmetics, according to the European Commission. Their use is increasing and they are therefore more likely to be released to the environment where they may have damaging effects on ecologically-important bacteria and other living organisms.
There is concern that silver nanoparticles contained in waste material or water may not be removed during processing, as treatment centres are typically not designed to remove nanoparticles. Sewage sludge (the output from wastewater treatment plants) may therefore contain silver nanoparticles and in many countries, sewage sludge is dried and applied as fertiliser on agricultural land. In Germany, for example, about 30% of the 2 million tonnes of dry sewage sludge solids collected from wastewater treatment plants is used to fertilise farmland.
In a study, the researchers investigated the effects of silver nanoparticles incorporated in sewage sludge on soil microorganisms. Over 90% of silver nanoparticles and almost all of the silver ions were absorbed onto the sewage sludge, implying the sewage treatment process did not remove the majority of the nanoparticles or ions. When the contaminated sludge was tested on soil samples over 180 days, the researchers saw similar effects as those that had occurred in the earlier 28 day tests with pure silver nanoparticles. The soil microorganisms were similarly inhibited – by both the silver nanoparticles and the silver ions – at 100 days after application. The full article is available here: European Commission