Inducement of denitrification and the resistance to elevated sulfamethoxazole (SMX) antibiotic in an Anammox biofilm system

Antibiotics have been widely utilized and are now found in many kinds of wastewater. The potential application of anaerobic ammonium oxidation (Anammox) to treat antibiotic-containing wastewater systems has attracted growing concern, so the long-term impact of the antibiotic sulfamethoxazole (SMX) on the Anammox process was investigated in this study. Thus, SMX (<30 mg L−1 concentration) was found to have a slight inhibitory effect on the Anammox process, with total nitrogen removal efficiency (TNRE) decreased to 76.7% from 82.4%. TNRE abruptly declined when SMX concentrations were increased to 30, 40, 50, and 70 mg L−1 and ultimately recovered to 61.0%, 59.9%, 63.2%, and 67.7%, respectively. Moreover, TNRE was significantly reduced to 28.3% and did not recover when SMX reached 90 mg L−1. After the termination of SMX addition, TNRE recovered to 83.5% after 44 days of operation. Denitrification was successfully induced to help the Anammox community resist the biotoxicity of SMX, with the relative abundance of Denitratisoma increased to 14.82% from 0.01%, after long-term exposure to SMX.