Study Of Sludge Oxidative Conditioning Process Based On Ferrous/Peroxomonosulfate System

In recent years,with the rapid development of industry,the continuous expansion of urban scale and the increase of population,the discharge of waste water is increasing unprecedented.Meanwhile,the by-product of waste water treatment,that is,the production of sludge,has also become a public concern.The existing sludge dewatering technology could not meet the requirement of moisture content in treated sludge,which restricts subsequent treatment processes.In this thesis,the mechanism of sludge oxidative conditioning process based on ferrous/peroxymonosulfate system was investigated.The aim of this study is to apply this system on different types of sludge to improve their dewaterability.The sludge types include:water supply plant sludge,primary sludge and secondary sludge.According to the changes of capillary suction time and specific resistance to filtration before and after treatment of water supply plant sludge,the parameters of optimum conditions were determined as follows.When the concentration of peroxymonosulfate was 0.5 g/g TSS,the concentration of Fe²⁺was 0.1 g/g TSS without pH adjustement,the reduction rate of capillary suction time was?65.67±1.03?%.The specific resistance to filtration decreased by?88.44±0.38?%.Through the determination of aluminium content in filtrate before and after oxidative conditioning of water supply plant sludge,it can be concluded that sulfate radical could improve the dewaterability of water supply plant sludge,while increasing the content of Al in the sludge filtrate.According to the changes of capillary suction time and specific resistance to filtration before and after oxidative conditioning of primary sludge,the optimum parameters were determined as follows:the concentration of peroxymonosulfate was 0.25 g/g TSS,when the concentration of Fe²⁺was 0.1 g/g TSS,the reduction rate of capillary suction time was?79.42±4.86?%,and the reduction rate of specific resistance to filtration was?95.46±0.80?%.After the primary sludge was oxidized,the particle size decreased by 44.02%,and the absolute value of zeta potential decreased close to zero.Scanning electron microscopy?SEM?showed that the surface of the sludge formed a lot of pores where free water could easily pass through.Through the determination of the changes of capillary suction time and specific resistance to filtration before and after oxidative conditioning of secondary sludge from two waste water treatment plants,the optimum parameters for oxidative conditioning of secondary sludge were also determined,respectively.The optimum parameters for the oxidative conditioning of secondary sludge in Nanshan waste water treatment plant were determined:peroxymonosulfate was 0.1 g/g TSS,Fe²⁺was 0.05 g/g TSS.Under this condition,the reduction rate of CST and SRF of sludge were?56.46±2.30?%and?89.26±0.02?%,respectively.The optimum conditioning parameters of secondary sludge in Futian waste water treatment plant were determined:peroxymonosulfate concentration was 0.1 g/g TSS,Fe²⁺concentration was 0.1g/g TSS,the reduction rate of capillary suction time was?64.57±2.92?%.The specific resistance to filtration decreased by?90.14±0.27?%.Therefore,the dewaterability of secondary sludge from Futian is slightly better than that of secondary sludge from Nanshan after oxidative conditioning.After treatment,the particle sizes and the absolute value of zeta potential of secondary sludge were decreased.However,the surface porosity of sludge increased.The concentrations of protein and polysaccharide decreased in TB-EPS,while increased in SB-EPS and LB-EPS.However,the total reduction of protein and polysaccharide in TB-EPS was much less than their increase in SB-EPS and LB-EPS,indicating that sulfate radical can enter the tight adhesion layer of extracellular polymer of sludge and destroy its structure.It could also destroy cells,convert more combined water into free water,and finally improve sludge dewaterability.