Activated Sludge in the Bioremediation of Water Containing SARS-CoV-2 Antivirals

The increasing presence of SARS-CoV-2 antivirals (SASs) in wastewater threatens aquatic ecosystems, making it necessary to better understand their removal efficiency during biological treatment. This study evaluates the removal percentages, kinetic mechanisms, and toxicity profiles of six SASs, daclatasvir (DCV), darunavir (DRV), favipiravir (FAV), lopinavir (LOP), remdesivir (REM), and ritonavir (RIT), using activated sludge. A full factorial design combined with response surface methodology (RSM) was used to assess the impact of pH, temperature (T), and mixed liquor suspended solids (MLSS) on SAS removal and microbial stability. The results distinguished two dominant removal pathways. DCV and LOP were primarily removed by adsorption, whereas DRV, FAV, REM and RIT were predominantly removed through biodegradation involving enzymatic transformation and bacterial co-metabolism. RSM achieved a desirability score of 0.772 and identified the optimal operating conditions (pH = 6.08, MLSS = 4.41 g/L, and T = 44.99 °C), resulting in removal efficiencies above 93% for all compounds except DRV, which remained the limiting compound with a maximum removal efficiency of 66%. Perturbation analysis showed that all tested factors have a distinct influence on process performance. These established kinetic trends should support further investigations into advanced biological wastewater treatment methods and precise ecotoxicity profiling of emerging biotransformation products.