Promising application of microalgal-bacterial granular sludge for 17α-ethinylestradiol removal: Effective...

Microalgal-bacterial granular sludge (MBGS) efficiently removes conventional contaminants, but its potential for estrogen transformation and detoxification remains unclear, which is a concerning topic for biological wastewater treatment of endocrine-disrupting contaminants. This study comprehensively investigated the fate, transformation, and detoxification of 17α-ethinylestradiol (EE2) in MBGS. Results demonstrated that MBGS showed superior performance to standalone Chlorella vulgaris and aerobic granular sludge, achieving 80.5% EE2 removal and 76.3% estrogenicity reduction. MBGS maintained robust performance and structural stability under various conditions. The primary EE2 removal pathways were biodegradation (58.2%) and photodegradation (30.5%). By leveraging both pathways, MBGS transformed photodegraded transformation products (TPs) into less estrogenic sulfate and glucuronide conjugates, resulting in a TP profile with significantly reduced endocrine, bioaccumulation, and developmental toxicity potentials. Therefore, MBGS represents a robust and sustainable solution for treating estrogenic wastewater, leveraging bacterial-algal synergy to eliminate both parent compound and the ecological risks from its TPs.