Effects of Hydrothermal Pretreatment and Anaerobic Digestion of Pig Manure on the Antibiotic Removal and Methane Production

Deciphering impacts of sulfadiazine on anaerobic co-digestion of pig manure and food waste for methane production

In this study, the impact of sulfadiazine (SDZ) at environmental and elevated levels on the integrated anaerobic digestion of pig manure with food waste was explored. Results showed that SDZ concentrations ranging from 50 and 450 mg/kg of total solids inhibited methane production by 3.3 % to 50.8 %. Moreover, SDZ hindered the acidification and methanogenesis processes but had minimal impact on the hydrolysis phase. Mechanism studies revealed that extracellular polymeric substances (EPS) absorbed and accumulated SDZ via amine, hydroxyl, and carboxyl groups. Then, SDZ incited microorganisms to secrete high amounts of EPS and reactive oxygen species. These compounds inhibited enzyme activity, thereby disrupting the processes of acidification and methanogenesis. Furthermore, SDZ remarkably reduced the populations of acidogenic bacteria and methanogens, rendering the microbial community inhospitable to methane generation. This study offers a noteworthy reference regarding the response of the anaerobic co-digestion system to various concentrations of SDZ.

Effects of hydrothermal pretreatment on sulfadiazine degradation during two-stage anaerobic digestion of pig manure

Antibiotics in animal manure pose significant risks to the environment and health. While anaerobic digestion (AD) is commonly used for pig manure treatment, its efficiency in antibiotic removal has been considerably limited. This study investigated the impact of hydrothermal pretreatment (HTP) on sulfadiazine (SDZ) removal in a two-stage AD system. Results indicated that the HTP process reduced SDZ concentration by 40.61%. Furthermore, the SDZ removal efficiency of the AD system coupling HTP increased from 50.90% to 65.04% compared to the untreated system. Biogas yield was also improved by 26.17% while maintaining system stability. Changes induced by HTP in the microbial communities revealed that Firmicutes, Bacteroidetes, Caldatribacteriota, and Proteobacteria emerged as the primary bacterial phyla. Following HTP, the relative abundance of Prevotella, which exhibited a strong negative correlation with SDZ concentration, increased significantly by 25-fold in the acidogenic stage. Proteiniphilum, Syntrophomonas and Sedimentibacter showed notable increases in the methanogenic stage after HTP. The N-heterocyclic metabolism carried out by Prevotella might have been the predominant SDZ degradation pathway in the acidogenic stage, while the benzene ring metabolism and hydroxylation by the Proteiniphilum emerged as the primary degradation pathways in the methanogenic stages. Furthermore, biodegradation intermediates were proven to be less toxic than SDZ itself, indicating that the HTP-enhanced two-stage AD process could be a viable way to lower the environmental risks associated with SDZ. The findings from this study provide valuable insights for removing SDZ from the environment via two-stage AD.