In-situ remediation of acid mine drainage using a permeable reactive barrier in Aznalcóllar (Sw Spain)

► A biological permeable reactive barrier to remediate acid mine drainage is reported. ► The PRB is successful to neutralize pH and remove heavy metals from groundwater. ► Sulfate is far from being completely reduced by sulfate-reducing bacteria (SRB). ► The poor SRB activity is due to short residence time and low substrate degradability.