Mechanisms of Bisphenol A Effect on Microbial Extracellular Polymers in Biological Denitrification Systems

Extracellular polymers (EPS) are critical for microbial metabolism in wastewater biological treatment processes. This study examined the impact of bisphenol A (BPA) on microbial EPS within a biological denitrification system. Results indicated that low concentrations of BPA (0.1, 0.5, and 1.0 mg/L) had minimal effects on denitrification performance. In contrast, high concentrations (3.0 and 5.0 mg/L) significantly impaired denitrification. As the concentration of BPA increased, tyrosine-like proteins content in loosely bound EPS (LB-EPS) increased while tryptophan-like proteins and humic acids content decreased. The C–(C,H) content in LB-EPS initially increased and then decreased, whereas the C–(O,N) content continuously increased. Conversely, in tightly bound EPS (TB-EPS), tyrosine and tryptophan-like proteins content decreased while humic acids content increased. The C–(C,H) content in TB-EPS continuously increased, whereas the C–(O,N) content initially increased and then decreased. The C–O–C and C=O peaks of polysaccharides and carboxylates in both LB-EPS and TB-EPS shifted, whereas the peaks corresponding to protein peptide bonds remained unchanged. BPA primarily binds to C–(C,H) and C–(O,N) components in EPS.