Electron beam irradiation for enhanced dewatering of dairy wastewater air flotation sludge: unravelling the demulsification and floc aggregation mechanism.

Dairy wastewater air flotation sludge (DWAFS) is resistant to conventional mechanical dewatering due to its high fat content and protein-stabilized emulsion structure. To address this challenge, this study employed electron beam (EB) irradiation as a pretreatment method. The effects of irradiation dose on sludge dewaterability were systematically investigated, and the multi-dimensional underlying mechanisms were elucidated through integrated multi-scale characterization. The results showed that EB irradiation significantly enhanced dewaterability, with 5 kGy identified as the optimal dose based on a combined evaluation of dewatering performance and specific energy consumption. EB irradiation was shown to efficiently disrupt the protein-stabilized emulsion, likely via water radiolysis-derived free radicals. This process is proposed to drive organic component transformation, surface charge neutralization, protein-lipid co-aggregation and floc reconstruction, ultimately contributing to the conversion of bound water to free water and enhanced dewaterability. These findings clarify the demulsification-dewatering coupling mechanism of EB irradiation on DWAFS and provide a theoretical basis for engineering application in high-fat oily sludge treatment.