Degradation of conjugated estrogen in visible light-driven intimately coupled photocatalysis and biodegradation system.

ABSTRACT

Visible light-driven intimately coupled photocatalysis and biodegradation (VDICPB) is an efficient technology for removing recalcitrant contaminants, but the degradation pathway on 17ß-estradiol 3-Sulfate (E2-3S) is still not clear. In this study, VDICPB based on N-doped TiO2 as a photocatalyst was established to investigate the removal and transformation of E2-3S in synthetic wastewater. VDICPB showed a satisfactory removal efficiency of 97.8 ± 0.4 %, which was much higher than that of independent photocatalysis (84.0 ± 2.2 %) or biodegradation system (71.4 ± 1.8 %). Steroid C/D-rings of E2-3S was broken in VDICPB since the transformation process reached terminal central pathway. Primary metabolites did not accumulate in VDICPB, resulting in a low expression of functional genes. E2-3S was mainly removed by cooperative interaction of photocatalysis and co-metabolism of biofilm. Photocatalysis led to deconjugation and microbes acted to mineralization. This study provides technical reference and theoretical support for the removal of new pollutants.