Effects of voltage on sulfadiazine degradation and the response of sul genes and microbial communities in biofilm-electrode reactors

Few studies have been performed on both the potential and the risks of biofilm-electrode reactors (BERs) with regard to the removal of antibiotics. This study used 33 BERs to investigate the removal rate and degradation pathway of sulfadiazine (SDZ). Furthermore, the effects of additional electrons on sul genes and microbial community composition were examined. The study found that rapid elimination rates of 20 mg/L SDZ were observed during the first 3 h with different DC voltage rates. Even high concentrations (160 mg/L) could be rapidly removed after 24 h of system operation. Pyrimidin-2ylsulfamic acid and aniline were noted to be principal products, and an SDZ degradation mechanism was proposed. The study identified 41 species of microorganism; based on bacterial community divergence caused by voltage, and six samples were grouped into four clusters. The relative abundances of sul genes from biofilm were in the following order: sulII > sulIII > sulI > sulA. The sulI, sulII, and sulA genes were enhanced with electrical stimulation in the cathode layer. It is noteworthy that sul genes were not detected in the effluent after 24 h of operation.