Screening Bioremediation for the Effective Removal of Regulated and Emerging Contaminants from Mining Wastewater

Mining wastewater contains complex mixtures of regulated and emerging contaminants that challenge treatment technologies. This study evaluates the bioremediation potential of 10 phytoplankton species, including Chlorella vulgaris, and the aquatic fern Salvinia natans for removing contaminants from synthetic and mine outflow water. Batch screening experiments were conducted using synthetic wastewater containing regulated elements, rare earth elements (REEs), or selected organic flotation reagents, followed by validation using acidic mine outflow water from a decommissioned mine (Romania). All tested phytoplankton species and Salvinia natans showed high removal efficiencies for several priority elements, including Pb, Ag, Cr, Th, U, and multiple REEs. Organic flotation reagents were efficiently removed by all phytoplankton species. Chlorella vulgaris and Salvinia natans emerged as high-performing species and were further evaluated in mine outflow, where species-specific and matrix-dependent removal behavior was observed. Here, Chlorella vulgaris showed a higher average removal. Time-resolved analyses indicated a rapid initial removal followed by equilibrium phases, suggesting biosorption and bioaccumulation mechanisms. Li and Se showed limited removal capacities across all species. Photosynthetic pigment analysis revealed stress responses in Salvinia natans under acidic, multielement exposure. Overall, phycoremediation and phytoremediation represent effective low-chemical treatment strategies with potential for integration into a complementary mining wastewater treatment workflow.