Functional fillers drive anaerobic treatment of high-sulfate organic wastewater in UASB reactors

This study investigates the role of functional fillers (i.e., granular activated carbon (GAC) and D201 ion exchange resin) in enhancing the anaerobic treatment of high-sulfate organic wastewater using an upflow anaerobic sludge blanket (UASB) reactor. Control and filler-amended reactors were operated to evaluate reactor stability, organic removal, methane production, and microbial community responses. The results show that the addition of functional fillers significantly improved reactor performance, with GAC exhibiting the most pronounced enhancement. Under high sulfate loading, the GAC-amended reactor increased COD removal efficiency from 76% to 81% while maintaining a stable effluent pH above 7. Methane production was simultaneously enhanced, with methane yield increasing by approximately 7% compared to the sulfate-fed control reactor. Furthermore, the optimal performance was achieved at a GAC-to-sludge volume ratio of 1:4, at which COD removal efficiency increased from 78% to 84%. Microbial community analysis showed an increased relative abundance of methanogenic archaea and sulfate-reducing bacteria in the GAC-amended system, consistent with enhanced syntrophic metabolism under sulfate-rich conditions. These findings demonstrate that appropriate filler selection and dosage can effectively improve process stability and energy recovery in UASB reactors treating sulfate-rich organic wastewater, providing practical guidance for industrial-scale UASB applications.