Innovative cation exchange-driven carbon migration and recovery patterns in anaerobic fermentation of waste activated sludge.

[Display omitted] • CE drove particulate carbon source dissolution by 34.72 % in 2-day treatment. • Remarkable carbon recovery rate of 21.37 % was achievable in 8-day fermentation. • 78.09–85.79 % of recoverable carbon sources were extracted by liquid separation. • CE-driven carbon migration and recovery were illustrated in negentropy pattern. Despite numerous treatments have been developed to enhance anaerobic fermentation of waste activated sludge, the innovative cation exchange (CE) approach has been rarely reported, little attempt was conducted to reveal carbon source fate. The interphase carbon balance was illustrated to clarify endogenous carbon dissolution, biotransformation,and recovery patterns. By CE-mediated divalent cation removal, almost 34.72 % of particulate carbon sources were dissolved in 2-day treatment, corresponding to soluble carbon content of 1165.58 mg C/L. Most of the originally dissolved carbon sources (58.01–66.81 %) were bio-transformed to volatile fatty acids with high bioavailability, while the further transformation to biogas was inhibited, contributing to recoverable carbon source accumulation. Overall, 21.38 % of total solid carbon sources were recovered through 8-day fermentation, the carbon extraction was implemented by solid–liquid separation with carbon loss of 14.21–22.91 %, manifesting the valid carbon recovery of 85.05–87.96 mg C/g VSS. Such CE-driven carbon recovery provided negentropy benefits in sustainable cycle economy. [ABSTRACT FROM AUTHOR]