Enhancement of sludge dewaterability using combined technology of bioleaching and Fenton: Microscopic structure and hydrophilic/hydrophobic properties of sludge particles

Bioleaching and Fenton technology are commonly used preconditioning techniques for sludge dewatering. This study compared the dewatering mechanisms of different conditioning technologies. The results showed that bound water, specific resistance to filtration (SRF), and capillary suction time decreased from 3.95 g/g, 6.16 x 1012 m/kg, and 130.6 s to 3.15 g/g, 2.81 x 10(11) m/kg, and 33 s, respectively, under combined treatment condition. Moreover, the free radicals, including center dot OH, O-2(-)center dot and Fe (IV), further damaged the cell structure, thus increasing the concentration of DNA in the S-EPS layer. This intense degradation sludge particle size decreased by 15.6% and significantly increased zeta potential. Under the combined technology, the alpha-helix and beta-sheet decreased by 42.2% and 56.5%, respectively, destabilizing the spatial structure of proteins and promoting the release of bound water. In addition, the combined technology decreased (Ala/Lys) ratio in the TB-EPS layer by 67.6%, indicating the weakening of protein water-holding capacity. Moreover, the conversion of oxygencontaining compounds to nonpolar hydrocarbons increased the hydrophobicity of the sludge under a combined treatment, thus enhancing dewatering performance.