Enhanced remediation of wastewater impacted by acid mine drainage at low temperature using sulfate-reducing bacteria immobilized in biomass-amended PVA-SA beads.

Acid mine drainage (AMD) is a severe environmental threat owing to its high acidity, sulfate, and heavy metal content with devastating effects on watershed ecosystems. In cold-climate mining regions, water temperature below 15 °C severely limits conventional bioremediation, as most functional bacteria are mesophilic. In this study, we tested the hypothesis that sulfate-reducing bacteria (SRB) capable of AMD remediation persist in cold mine environments and that their activity can be enhanced via gradient cold acclimation. Indigenous functional consortia were enriched and acclimated from AMD-contaminated sediments collected in the Shandi River basin, China. Metagenomic analysis confirmed the dominance of Desulfovibrio, the presence of complete dissimilatory sulfate reduction pathways, alongside cold-adaptation and acid-tolerance genes. Free-living cells were then immobilized in polyvinyl alcohol-sodium alginate (PVA-SA) beads containing corn straw pretreated with raw AMD. The results demonstrated that the beads possessed a porous network structure and enabled sustained carbon source release, attaining a sulfate removal efficiency of 98.5% in synthetic mining wastewater (SMW) at 12 °C. Solid-phase characterization verified that sulfate and heavy metals were transformed into stable crystalline phases. Furthermore, Microbial community profiling revealed that fermentative bacteria dominated the consortium, which could convert straw into bioavailable substrates that sustained SRB metabolism. These results demonstrated that immobilized bacteria were potentially and practically applied to AMD-impacted wastewater remediation despite the cold climate.