Abstract
<jats:p>This study quantified the removal and biotransformation of the industrial enzymes subtilisin and α-amylase in wastewater treatment plants (WWTPs) and activated sludge systems. Measurements of subtilisin and α-amylase at an industrial WWTP showed high inlet concentrations and concentrations below quantification limits in the outlet, corresponding to removals of more than 99% of intact enzymes. Lower concentrations of the enzymes were found in the inlet to a municipal WWTP at which the concentrations in the outlet were below the quantification limits. Complementary laboratory simulation experiments with activated sludge demonstrated extremely rapid biotransformation of subtilisin and α-amylase under aerobic conditions. More than 70% of the intact enzyme protein was lost within 0.25 min, and more than 90% within 5 min, followed by slower continuous transformation to levels below quantification limits within 48 h. The transformation followed first order kinetics with Disappearance Time 50 (DT50) values of less than 10 seconds for both enzymes. In contrast, only minor losses were observed in abiotic sludge, indicating that microbial degradation is the primary removal mechanism. Overall, the results show that subtilisin and α-amylase are rapidly transformed during wastewater treatment, supporting the assumption of very low environmental concentrations and providing robust data for environmental exposure modelling.</jats:p>