Unraveling Biodegradation Mechanisms of Favipiravir by the Partial Nitritation Granular Sludge

This study successfully established a laboratory-scale partial nitritation granular sludge sequencing batch reactor (SBR) under the condition of high ammonia nitrogen and high temperature. During the stable phase of the SBR, the average ammonia nitrogen removal efficiency attained 75.6%, the average nitrite accumulation rate was 82.5%, and the average particle size of the granular sludge achieved 433.1 ± 107.9 μm. In addition, the removal efficiency of chemical oxygen demand reached 91.3%. Simultaneously, using favipiravir as the target pollutant, the biodegradation efficiency of favipiravir by the partial nitritation granular sludge was investigated by batch tests. The test revealed that in the ammonium-added group, the removal efficiency of favipiravir reached approximately 25.1% at 144 hours. And the biomass-normalized removal rate constant achieved approximately 0.0018 L/g VSS/h. The removal of favipiravir was attributed to co- metabolic degradation induced by ammonia-oxidizing bacteria.