The extensive use of antiviral substances (SASs) during and after the COVID-19 pandemic has increased their release into wastewater systems, raising concerns regarding their persistence and potential ecotoxicological effects. The primary objective of this study was to isolate bacterial strains from activated sludge (AS) that possess the ability to biodegrade SASs. From the AS sample, three bacterial species, Comamonas testosteroni (I2), Bacillus amyloliquefaciens (I3) and Bacillus mycoides (I4), were successfully isolated and identified. These strains were subsequently applied in biodegradation experiments targeting seven SASs: daclatasvir (DCV), darunavir (DRV), favipiravir (FAV), lopinavir (LOP), remdesivir (REM), ritonavir (RIT), and umifenovir (UMI). During the experiments, residual SAS concentrations, microbial growth parameters, physicochemical indicators and ecotoxicity were monitored. All three strains demonstrated substantial biodegradation potential, achieving reductions exceeding 90% for most tested compounds, with particularly low toxicity observed in experiments conducted with AS and Bacillus amyloliquefaciens. These findings highlight the relevance of AS-derived bacteria as promising candidates for enhancing SAS removal in wastewater treatment processes.

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.

This study investigated the removal of SARS-CoV-2 antivirals substances (SASs) in wastewater treatment systems through kinetic analysis and response surface modeling based on a full factorial experimental design (3³). Quadratic models best described the removal of most SASs, revealing nonlinear interactions among experimental factors and identifying the SASs mixture ratio as the key determinant of removal efficiency. Based on their removal behavior, the investigated SASs were classified into three groups: reversible adsorption (FAV, REM), enhanced bioavailability (DCV, DRV) and irreversible adsorption (LOP, RIT). LOP and RIT exhibited the highest adsorption affinities and formed the initial layer on activated sludge, whereas the limited removal of DRV and FAV reduced the overall treatment efficiency. The increased bacterial Colony-Forming Unit (CFU) suggests enhanced microbial activity, which may have promoted extracellular polymeric substance (EPS) production, contributing to reduced toxicity toward Aliivibrio fischeri. Finally, integrating RSM-derived polynomial models with artificial intelligence offers a promising approach for predicting and optimizing the removal of SARS-CoV-2 antivirals in conventional wastewater treatment plants.