Environmentally-grown aerobic granular sludge performs more complete pharmaceutical biodegradation and wastewater treatment than lab-grown granules

Abstract

This study evaluated pharmaceutical removal by environmentally-grown aerobic granular sludge (AGS). Most pharmaceutical treatment studies utilize lab-grown AGS, which is cultivated from activated sludge flocs on synthetic media and therefore is likely to possess different physical and microbiological properties than its real-world counterpart. For approximately 70 days, a 60 μg/L mixture of gemfibrozil, diclofenac, and erythromycin was fed to environmentally-grown AGS. Wastewater treatment, granule characteristics, and pharmaceutical fate were monitored. Environmentally-grown granules outperformed their lab-grown counterparts in multiple ways: environmental granules were physically unimpacted by pharmaceuticals, phosphate removal remained complete, and all nitrogen removal processes were unaffected except ammonia oxidation, which was temporarily inhibited by approximately 35%. Most importantly, gemfibrozil was completely biodegraded, a result yet to be observed in any AGS study. Diclofenac and erythromycin removal were minimal and generally below 10%. The families J111, Xanthomonadaceae, OLB5, and Weeksellaceae were uniquely identified as pharmaceutical degraders. Results suggest that environmentally-grown AGS contains rare, but essential, microbial community members missing from lab-grown granules, and these communities enhance environmental granules’ resilience during pharmaceutical exposure. Altogether, this study demonstrates that lab-grown AGS may not accurately model the functional capacity of its real-world counterparts.