Enhancing hydrogenotrophic activities by zero-valent iron addition as an effective method to improve sulfadiazine removal during anaerobic digestion of swine manure

In this study, the feasibility of Fe 0 addition for driving sulfadiazine (SDZ) removal during anaerobic digestion of swine manure (SM) was tested. Compared with the Fe 0 -free digesters spiked with 200 mg/L SDZ (R SDZ ), treatments with 5.0 g/L Fe 0 (R SDZ/Fe 0 ) significantly accelerated and optimized the acidification process by enriching Clostridia and Bacteroidia (key members responsible for VFAs/H 2 production), providing more readily available substrates for methanogenesis. Furthermore, Fe 0 increased the overall abundance of hydrogenotrophic methanogens, specifically toxicant resistant Methanoculleus and Methanosphaera spp. were selectively enriched, helping achieve a 36.9% higher CH 4 yield and a 26.4% greater total solids removal efficiency. A positive correlation between the solid content and the SDZ concentration adsorbed in SM was observed. The addition of Fe 0 increased the distribution of SDZ in liquid and facilitated its removal through the enhanced biodegradation and physicochemical processes. Overall, the total SDZ removal efficiency was improved by 86.8% with Fe 0 .