1,3-Dichloro-5,5-dimethylhydantoin (DCDMH)-Driven Sludge Pretreatment for Organic Carbon Valorization: Mechanistic Insights into Controlled Oxidative Disruption and Hormesis-Mediated Metabolic Reshaping

Organic carbon valorization via anaerobic sludge fermentation is intrinsically constrained by biopolymer recalcitrance and methanogenic diversion. We introduced 1,3-Dichloro-5,5-dimethylhydantoin (DCDMH) pretreatment leveraging controlled oxidative disruption and microbial metabolic regulation to boost short-chain fatty acid (SCFA) production. At optimal dosage (0.025 g/g TSS), SCFA yield increased by 192.1%, driven by enhanced substrate liberation and biochemical conversion. Molecular docking and 2D-COS FTIR analyses collectively indicate that the N-Cl moiety of DCDMH preferentially oxidized hydrophobic proteins within extracellular polymeric substances, while the derived HClO could penetrate cells to damage intracellular components. This dual action disrupted structural integrity, accelerating macromolecular substrate release and conversion, and enriching stress-tolerant hydrolytic/acidogenic bacteria. Sustained HClO release established oxidative stress wherein reactive oxygen species (ROS) functioned as metabolic signals beyond mere damage indicators. Moderate intracellular ROS stress stimulated substrate acidogenesis while suppressing methanogenic carbon sinks, and enhanced the gene abundances associated with antioxidant defenses and acidogenic pathways. Crucially, this work reveals for the first time the hormetic effect of DCDMH-derived HClO on acidogenic metabolism, providing a new insight into the application of chlorine-containing disinfectants in related fields.