Comprehensive insights into the organic/inorganic composition separation of sewer sediment by various driving forces: Separation pathway and thermodynamic evolution

With the legislative development, the organic and inorganic composition separation has become the primary requirement for sewer sediment disposal, however the relevant technology has been rarely reported and the driving mechanism was still unclear. In this study, direct disintegration of biopolymers and indirect broken of connection point were investigated on the hydrolysis and component separation. Three typical sewer sediment treatment approaches, i.e., alkaline, thermal and cation exchange treatments were proposed, which represented the hydrolysis-driving forces of chemical hydrolysis, physical hydrolysis and innovative cation bridging breakage. The results showed that the organic and inorganic separation rates of sewer sediment driven by alkaline, thermal and cation exchange treatments reached 21.26 %, 23.80 %, and 19.56 %-48.0 %, respectively, compared to 4.43 % in control. The secondary structure of proteins was disrupted, transitioning from α-helix to β-turn and random coil. Meanwhile, much biopolymers were released from solid to the liquid phase. From thermodynamic perspective, sewer sediment deposition was controlled by short-range interfacial interactions described by extended Derjaguin-Landau-Verwey-Overbeek theory. Additionally, the separation of organic and inorganic components was positively correlated with the thermodynamic parameters (Corr = 0.87), highlighted the robustness of various driving forces. And the flocculation energy barriers were 2.40 (alkaline), 1.60 times (thermal), and 4.02–4.97 times (cation exchange) compared to control group. The findings revealed the contrition difference of direct disintegration of gelatinous biopolymers and indirect breakage of composition connection sites in sediment composition separation, filling the critical gaps in understanding the specific mechanisms of sediment biopolymer disintegration and intermolecular connection breakage.