Occurrence, Fate and Mass Balance of Sixty-Eight Natural and Synthetic Glucocorticoids in a Municipal Wastewater Treatment Plant

Glucocorticoids (GCs) are emerging endocrine-disrupting chemicals that may threaten aquatic organisms even at ng/L levels. Wastewater treatment plants (WWTPs) therefore serve as a critical barrier preventing GCs from entering the environment. To elucidate their occurrence and fate, we quantified 68 natural and synthetic GCs and performed a mass balance in a WWTP operating an anaerobic–anoxic–aerobic process. In the influent, 36 GCs were detected, with a total dissolved concentration of 4156 ng/L. Sixteen cortisol derived metabolites dominated the natural GC profile (4073 ng/L), whereas cortisol itself was present at only 20 ng/L. Among synthetic GCs, hydrocortisone-type compounds showed the highest concentrations, followed by several less-studied ester analogues. Natural GCs (except 11α-THCRL), hydrocortisone types, betamethasone types and labile prodrug esters were readily removed from the dissolved phase (82%–100%). In contrast, acetonide types (58–90%) and halogenated esters (15–92%) showed higher persistence. Mass balance analysis showed that GCs were removed mainly through biodegradation, with mass losses of 59–100%. Across the treatment train, 0–16% and 0–94% of the initial load were discharged via sludge and effluent. The substantial proportion released with the effluent highlights a major pathway through which GCs enter aquatic environments and potentially exert ecological risks.