Synergetic pretreatment of waste activated sludge by Fe(II)-activated persulfate oxidation under mild temperature for enhanced dewaterability

► No study carried out on the combined thermal-Fe(II)-S2O82− oxidation pretreatment. ► Sludge dewaterability was enhanced by Fe(II)-S2O82− oxidation in mild temperature. ► 94-96% CST reduction efficiency was obtained within the first 5 min. ► Tyrosine and tryptophan protein-like matters in EPS mainly affected the dewatering. ► The treatment destroyed EPS, releasing EPS-bound water and interstitial water.