Pollutant removal performance and microbial responses of pure moving bed biofilm reactor to the successional sulfadiazine exposure

Abstract

Pure Moving bed biofilm reactor (pure MBBR) with biofilm as biomass core is a viable process for treating antibiotics. The influences of sulfadiazine (SDZ) on pure MBBR have yet to be investigated in depth. This study examined the responses of biofilm exposure to different doses of SDZ (0, 1, 3, 5, 7 and 10 mg/L) in the pure MBBR. Under continuous-flow conditions, pure MBBR held a high SDZ removal rate, but SDZ significantly inhibited COD and TN removal. However, 1–3 mg/L SDZ could enhance NH4+-N and TP removal. And these observations were confirmed by biomass analysis and multi-omics sequencing data. SDZ accelerated the sloughing and renewal of aerobic biofilm, thus shortening the solids residence time. The biofilm communities were strongly shifted by SDZ and the activity of autotrophs was less inhibited by SDZ than that of heterotrophs. Meanwhile, SDZ did not alter the biofilm's primary nitrogen metabolism mechanism, while disrupting the ratio of denitrification genes to nitrification genes. SDZ effectively promoted the gene expression of amoCAB and hao, but restrained norBC. The increased abundance of resistance genes Sul1–3 was a major reason for the biofilm could adapt to the high concentration of SDZ. Overall, the pure MBBR could operate well when SDZ was below 3 mg/L. This study provided new insight into antibiotic wastewater treatment through pure MBBR.