Insights into mechanisms of bisphenol A biodegradation in aerobic granular sludge

Wastewater is the major source of bisphenol A (BPA) in the environment, however, the results regarding main mechanisms of BPA biodegradation in wastewater treatment systems are divergent. The effect of BPA concentration in wastewater (0, 2, 6, 12 mg BPA/L) on respirometric activity and expression of selected genes in aerobic granules was examined. A real-time protocol for analysis of direct BPA-degrader activity targeting gene coding for ferredoxin was developed. At 2 mg BPA/L, respirometric activity of granules was the highest, which favored the fastest pollutant removal, and BPA-degraders were active at the beginning of the reactor cycle and no by-products of BPA degradation were detected. At 6 and 12 mg BPA/L, the activity of BPA-degraders was much higher, peaking after feeding and again when a BPA metabolite (3-(benzyloxy)benzoic acid) appeared in the reactor. The upregulation of gene coding for ammonia monooxygenase indicated that co-metabolism occurred mostly at 12 mg BPA/L.