Enhanced dewatering extent of sludge by FeO-driven heterogeneous Fenton.

Homogeneous Fenton (Fe/HO) serves as a high-efficiency conditioning method for sludge dewatering due to the generation of strong oxidizing hydroxyl radicals (OH). However, high dose of ferric salts produces iron-rich dewatered sludge and decrease sludge organic matters, which will not be conducive to the subsequent disposal and reutilization. Considering advantages of FeO as heterogeneous Fenton catalyst, FeO-activated HO (FeO + HO) in this study was adopted to improve sludge deep-dewatering. Reduction efficiency of the bound water (71.3 %) after FeO + HO treatment (after a reaction time of 30 min) were much higher than those in the Fe+HO treatment. Especially, the moisture content of treated sludge cake by FeO + HO remarkably decreased from 86.4 % to 61.3 %. Improvement mechanism of sludge dewatering after FeO + HO treatment mainly included electrostatic neutralization, reactive radical oxidation, and skeleton building by analysis of contribution factors. The generation of H in acidification could neutralize the negatively charged compounds to promote sludge hydrophobicity. Meanwhile reactive radicals generated from FeO + HO destroyed sludge extracellular polymeric substances and cell structure to release intracellular water. Furthermore, FeO as a skeleton builder could reconstruct destructive sludge flocs and form new dewatering channels. Finally, low Fe leaching content and recoverability of FeO effectively will decrease environmental implication.