Simultaneous effects of nanoscale zero-valent iron on wastewater decontamination and energy generation: Mechanisms of sulfamethoxazole degradation and methanogenesis

The presence of sulfamethoxazole (SMX) can adversely affect the anaerobic digestion process, reducing the efficiency of wastewater treatment and methane production. In this study, the addition of exogenous nanoscale zero-valent iron (nZVI) enhanced the efficient treatment of SMX and promoted the energy recovery from antibiotic wastewater. The results showed that the removal of SMX in the reactor pairs with 0.5 g/L nZVI increased by 20 %, 35 %, and 27 %, and the methane production increased by 21.6 %, 40.9 %, and 26.6 %, respectively, compared with the control reactor at different SMX influent concentrations (50, 100, and 200 mg/L). The microbial community distribution indicated that the nZVI facilitated efficient cooperation between acid-producing and methanogens by regulating the relative abundance of functional bacteria, such as Anaerolinea and Methanothrix. Meanwhile, nZVI can effectively facilitate the direct interspecies electron transfer (DIET) and enhance electron transport system (ETS) activity by functioning as a conductive particle and increasing the abundance of genes related to cytochrome C (Cyt C) and type IV pili. In addition, nZVI can reduce the risk of antibiotic resistance genes (ARGs) transmission by decreasing the relative abundance of ARGs. In summary, this study could provide new insights and theoretical support for efficient anaerobic bioremediation and energy recovery of antibiotic wastewater containing SMX.