Effects Of Fe⁰/Fe₃C@CS Activated PMS And Peroxone-Fe??? Conditioning On Activated Sludge Dewaterability

With the rapid increase of wastewater production in China,the treatment and disposal of a large amount of excessive sludge produced by wastewater treatment plants has become an urgent problem to be solved.For activated sludge?AS?dewatering and volume reduction,this study investigated the effects of magnetic nano zero-valent iron encapsulated in carbon spheres?Fe⁰/Fe₃C@CS?excited peroxymonosulfate?PMS?conditioning and peroxone disintegration-Fe??? coagulation joint conditioning?peroxone-Fe??? ?on AS dewaterability,optimized the operating conditions,revealed the migration and transformatifaon of organic matters in extracellular polymeric substances?EPS?.In addition,for peroxone-Fe??? joint conditioning and horizontal electro dewatering combined process?peroxone-Fe??? -HED?,its mechanism was identified based on the changes in sludge morphology,water composition and protein secondary structures.The results are as follows:For Fe⁰/Fe₃C@CS excited PMS conditioning,when the dosages of Fe⁰/Fe₃C@CS and PMS were 35.9 mg/g total suspended solids?TSS?and 0.43 g/g TSS,respectively,the AS filtered water content decreased to 69.45%.The conditioning process could destroy the phenolic group in the protein long-chain structure on the complex substance of protein and polysaccharide.Moreover,the tightly bound EPS?TB-EPS?and loosely bound EPS?LB-EPS?in AS were cracked,making a portion of polysaccharides and proteins migrate to slime,resulting in the contents of the two substances increased by 0.15 g/g TSS and 4.85 g/g TSS,respectively,and humic acids were released from the cell phase into EPS.The total fluorescence intensities of typical organic substances in TB-EPS and LB-EPS decreased from 760.26×107 AU·nm2 to 38.43×107 AU·nm2,indicating that the content of hydrophilic substances decreased,which was beneficial to sludge dewatering.However,the filtered water content of the AS after Fe⁰/Fe₃C@CS excited PMS conditioning was still high,and the dewaterability of the AS needs to be further improved.In order to improve the conditioning performance on AS,this study further used peroxone-Fe??? joint conditioning combined with HED to reduced AS volume.When the O3 flow rate was 1.50 L/min,the dosages of H2O2 and Fe??? were 5.7 g/g TSS and 0.083 g/g TSS,respectively,the AS water content after HED reduced to 84.88%,the bound water and free water contents were reduced by 1.88 g/g TSS and 40.81 g/g TSS,respectively.HO· could disintegrate the structure of EPS and cells,release bound water and amount of organic matters.Moreover,under the oxidation of HO·,the protein structure?such as-CO-NH-?was destroyed,resulting in the decrease of proteins water affinity.At the subsequent Fe??? flocculation stage,the broken sludge fragments and EPS components were re-aggregated,the water flow channels ware built,and the proportion of ?-helix in slime was further reduced,then sludge dewaterability was improved.At HED stage,the contents of bound water and free water in AS were further reduced and finally the sludge volume reduction was achieved.