The biofiltration process by the bivalve D. polymorpha for the removal of some pharmaceuticals and drugs of abuse from civil wastewaters

•We tested the use of zebra mussel in the wastewater treatments plants (WWTPs).•A pilot-plant was built in the largest WWTP of Milan (Italy).•Several preliminary tests were carried out to improve the operative plan.•Zebra mussels are able to produce a decrease of several pharmaceuticals and drugs of abuse.•It represents a natural and not expensive way to polish biologically treated effluents.

This study shows the evaluation of the possible use of the freshwater bivalve Dreissena polymorpha for the removal of some recalcitrant contaminants, namely many pharmaceuticals and drugs of abuse that are not sufficiently removed from civil wastewaters. This mollusk has an enormous filtering capability and is highly resistant to natural and anthropogenic stresses and to a significant bioaccumulation of lipophilic contaminants. All these characteristics may be particularly useful for the removal of compounds not easily eliminated by conventional wastewater treatment processes. To verify this hypothesis an experimental study was conducted at the pilot scale using a pilot plant installed in the largest wastewater treatment plant of Milan (Milano-Nosedo, Italy). First, we presented results obtained in several preliminary tests in order to evaluate the capability of zebra mussel specimens to survive in different wastewater mixtures, its filtering capacity and the possible influence of bio- and photo-degradation in the abatement of the molecules of interest. Finally, data obtained in the final tests demonstrated a capacity of this filter-feeder to reduce the concentrations of several pharmaceuticals and drugs of abuse higher than that obtained by the simple natural sedimentation, suggesting a possible implementation of the bio-filtration process in wastewater management.