Removal of Favipiravir from Wastewater with Membrane Bioreactor: Operational Parameters, Kinetics and Risk Assessment

Antiviral drugs, especially those used to treat COVID-19, have recently been classified as emerging pollutants due to their persistent presence in water and wastewater. These compounds have been found in environmental matrices around the world, demonstrating that existing treatment methods are ineffective in fully removing them from water and wastewater. Therefore, this study examines the removal of favipiravir (FAV) in synthetic domestic wastewater using a membrane bioreactor (MBR). The MBR was operated at varying initial FAV concentrations (50, 100, and 150 µg/L) and solid retention times (SRTs) (45, 30, and 15 days). FAV concentration was measured in aqueous phase (influent and effluent) and sludge samples. Based on the obtained results, the biological degradation constant and efficiency of pharmaceutical removal were determined. An environmental risk assessment was also conducted. Results showed that FAV degradation rate was slightly decreased with increasing initial FAV concentration. However, FAV was removed > 99% regardless of initial FAV concentration. As the initial FAV concentration increased from 50 µg/L to 150 µg/L, the FAV concentration in sludge samples decreased, ranging from 90.8 μg/g to 41.3 μg/g. FAV removal efficiency increased from 48.9% to 86.4% with increasing SRT. The study of environmental risk quotients (RQ) indicates high risk of FAV (RQ > 1).