Enhancing The Sludge Dewaterability By Electrolysis/electrocoagulation Combined With Zero-valent Iron Activated Persulfate Process

A vast amount of waste activated sludge(WAS)is produced in China,and inappropriate treatment and disposal of WAS may bring about serious secondary pollution.In sludge treatment,the sludge dewatering is a key step for the volume reduction of WAS.However,the poor performance of WAS dewatering seriously restrict subsequent sludge disposal.With high content of organic matter,WAS is strong hydrophilic and contains a great amount of bound water in sludge extracellular polymeric substances(EPS)and cell,worsening the sludge dewaterability.Thus,it is imperative to condition sludge before dewater it.Activated persulfate oxidation technology is able to generate powerful SO4-· with stable oxidation ability in neutral pH,which can destroy the hydrophilic structure of the sludge.In addition,electrochemical pretreatment is an efficient green technology which will not leads to secondary pollution.In this study,the innovatively hybrid process of electrolysis/electrocoagulation and zero-valent iron activated persulfate oxidation(EZP)showed a significant synergetic effect in enhancing municipal sludge dewaterability,and has the potential for enhancing industrial sludge dewaterability.The optimal dewatering conditions for municipal sludge were voltage 40 V and 4.15 g/L Na2S2O8 when zero-valent iron induced electrodes were applied.After EZP pretreatment,the municipal sludge specific resistance to filtration(SRF)and capillary suction time(CST)decreased by 87.4%and 49.1%respectively.The effects of EZP pretreatment on zeta potential,EPS property,viscosity and dewaterability of different sludge were analyzed to unravel the underlying mechanism of sludge conditioning.Results showed that the EZP oxidation was capable to effectively disrupt the EPS,crack the entrapped cells,and degrade the protein-like substances,reducing the viscosity and negative zeta potential,releasing bound water inside EPS and cells and thus improving sludge dewaterability.According to the analysis of Three-dimensional excitation emission matrix(3DEEM),the EZP technology greatly decomposed tryptophan and aromatic protein-like substances in EPS.Scanning electron microscope(SEM)analysis further revealed that the disrupted EPS and cells were coagulated after EZP conditioning and reinforced sludge dewatering.The preliminary economic analysis showed that the optimized EZP was economically favorable.