Sulfonamide degradation and metabolite characterization in submerged membrane photobioreactors for livestock excreta treatment

Residual veterinary antibiotics have been detected in livestock wastewater treatment plants. Despite the long retention time, antibiotic treatment efficiency has shown clear limitations. In this study, we evaluated submerged membrane photobioreactors (SMPBR) during sulfonamide antibiotic-containing livestock wastewater treatment under mixotrophic and photoautotrophic conditions. The results showed that microalgal sulfur degradation and consumption under mixotrophic conditions accelerated the biomass concentration increase to 2800 mg VSS/L compared to the 1800 mg VSS/L measured under photoautotrophic conditions. Although microalgal metabolites, such as soluble microbial products and extracellular polymeric substances, might cause membrane fouling in the SMPBR, we proved that microalgae could remove sulfonamide and release degradation-associated sulfur, along with nitrogen and phosphorus. Moreover, this study confirms the statistical correlation between metabolites and sulfonamides. In summary, the results of this study provide promising insights into antibiotic-containing livestock wastewater treatment.