Improving Waste Activate Sludge Dewatering Performance Using Sodium Periodate Oxidation On Extracellular Polymeric Substances

Sewage treatment plants will produce a large amount of residual sludge with a water content of 60%to 80%.Some sludges contain heavy metals,Escherichia coli,other toxic and harmful chemicals.These sludges require further sludge treatment and dispose.Further dewatering the remaining sludge will facilitate the transportation,storage,treatment and disposal of the sludge,and reduce the cost of subsequent disposal.Sodium periodate?NaIO₄?is a kind of advanced oxidant with selective oxidation ability.In this study,NaIO₄ was used for the first time as an oxidant to improve sludge dewatering.The results and research content are as follows:The oxidation effect of NaIO₄ on sludge extracellular polymeric substances?EPS?was investigated and the combined conditioning of NaIO₄ and APAM was used to improve sludge dewatering.The results showed that NaIO₄ oxidized sludge could change the distribution of protein and polysaccharide in EPS,NaIO₄ and APAM combined conditioning effectively improve the sludge dewatering performance.When 0¹76 mg/g DS?dry solids?NaIO₄ was added to the sludge,the contents of protein and polysaccharide in soluble EPS?S-EPS?increased,and the contents in loosely bound EPS?LB-EPS?decreased,while causes a decrease the contents of humic acid in S-EPS.When 88 mg/g DS of NaIO₄ and 2 mg/g DS of APAM was added to the sludge,the specific resistance of sludge decreased from 12.94×10¹² m/kg to4.82×10¹² m/kg of the original sludge,and the water content reduced from 94%of original sludge to 69.67%after suction filtration.After NaIO₄ oxidation,the median particle size of the sludge decreased,the sludge flocs destroyed by oxidation and the electronegativity of the Zeta potential of the sludge decreased.The effect of adjusting the pH of sludge and the addition of NaIO₄ on the sludge EPS was studied.The results showed that the organic contents of EPS changed after oxidation.As the pH of the sludge decreased,the protein content in S-EPS increased,and the protein contents in LB-EPS decreased;as the dosage of NaIO₄ increased,the protein content in S-EPS increased first and then decreased,protein in tightly bound EPS?TB-EPS?content was reduced.The response surface method?RSM?experimental results showed that when the sludge pH was adjusted to 6.5,the NaIO₄ addition amount was 50 mg/g DS,and the APAM addition amount was 5 mg/g DS,the SRF was reduced from 15.64×10¹² m/kg of original sludge to 1.94×10¹²m/kg,and the water content was reduced from 94%of original sludge to 79.56%after suction filtration,the sludge dewaterability was significantly improved.The mechanism of pH+NaIO₄+APAM to improve sludge dewatering was further studied by adding different chemical conditioning combinations.Through acidification,NaIO₄ pre-oxidized sludge EPS and degraded protein and other substances in EPS,and then APAM coagulated to reduce the sludge Zeta potential.And the small particles of the sludge were aggregated into large particles,thereby improving the dewatering effect of the sludge.The C-OH and C-O peaks in S-EPS increased after sludge acidification and oxidation,the Zeta potential electronegativity of sludge decreased,and the bound water content decreased.The particle size of the sludge was oxidized by the original sludge?59.60?m?and then crushed?53.86?m?,and then re-coagulated by APAM re-flocculation?88.87?m?.