The metallic element pollution is a serious environmental problem but still unsolved since these
contaminants are released mainly by human activity, reaching all the environmental compartments.
Traditional wastewater treatment plants are very efficient in removing metallic elements only when their
concentration is in the order of mg/L, but are not able to remove them until mg/L, as it would be needed to
cope with the water quality standards in low
flow receptors. Therefore, the aim of our study was to
evaluate the potential removal of some recalcitrant metallic elements to the classical treatments, by the
natural process of bio-filtration performed by the invasive zebra mussel (Dreissena polymorpha). For this
purpose we built a pilot-plant at the Milano-Nosedo wastewater treatment plant, where we placed about
40,000 D. polymorpha specimens appointed to the wastewater bio-filtration. The metallic element
removal due to zebra mussel activity was evaluated in the treated wastewater with a plasma optical
emission spectrometry (ICP-OES). Data obtained in these experiments showed an encouraging metallic
element removal due to D. polymorpha activity; in particular, the total abatement (100%) of Cr after one
day of bio-filtration exposure is remarkable. Therefore, this study encourages further research related
with the use of bivalves as a new tool for the wastewater depuration process; in this regard, the
contaminated mollusks used in the bio-filtration could be incinerated or stored in special landfills, as is
also the case of traditional sewage sludge.