Removal of FePO4 and Fe3(PO4)2 crystals on the surface of passive fillers in Fe0/GAC reactor using the acclimated bacteria

► Fe3(PO4)2 and FePO4 crystals would weaken treatment efficiency of Fe0/GAC reactor. ► Fe3(PO4)2 and FePO4 crystals could be removed by the acclimated bacteria. ► FeS and sulfur in the passive film would be removed by the sulfur-oxidizing bacteria. ► Develop a cost-effective bio-regeneration technology for the passive fillers.