Mineralization of steroidal hormones by biosolids in wastewater treatment systems in Tennessee USA

During the past several years, concern has risen over potential pollution of waterways with estrogenic compounds, including steroidal hormones from human and animal sources. One potential source of steroid hormone contamination is through the incomplete removal of these compounds in wastewater treatment systems (WTS). To address this issue, laboratory mineralization assays using C-14-labeled estrogens and testosterone were performed with biosolids from four municipal treatment plants and one industrial system. The importance of adapted microbial populations in the removal of estrogen was shown by the dramatic differences in mineralization of C-14-17 beta-estradiol by biosolids from a municipal plant compared to that from the industrial plant, 84% versus 4%, respectively. Indeed, biosolids from all of the municipal plants mineralized 70-80% of added C-14-17 beta-estradiol to (CO2)-C-14 in 24 h. Removal of C-14-17 beta-estradiol from the aqueous phase by biodegradation and/or biosorption to cell matter was greater than 90%. A recombinant yeast estrogen assay (YES assay) also confirmed that biological estrogenic activity was removed from the biosolid samples to below the detection limit (1.56 nM). C-14-Testosterone was mineralized to (CO2)-C-14 in all four municipal biosolids in amounts ranging from 55% to 65%; moreover, total removal of C-14-testosterone from the aqueous phase was 95%. First-order rate constants k were obtained for the mineralization and removal from the aqueous phase of natural and a synthetic steroid hormone in biosolids from one WTP. In these biosolids, C-14-17 beta-estradiol and C-14-testosterone were rapidly mineralized to C-14-CO2 (k = 0.0042 +/- 0.0002 min(-1) and 0.0152 +/- 0.0021 min(-1), respectively), whereas the mineralization of the synthetic estrogen C-14-17 alpha-ethinylestradiol was 25-75-fold less (k = 0.0002 +/- 0.0000 min(-1)). In addition, mineralization of C-14-ethinylestradiol did not reach completion in 24 h with only 40% mineralized to C-14-CO2. Approximately 20% of the C-14-ethinylestradiol remained in the aqueous phase and was biologically active as determined by the YES assay. Changes in temperature of approximately 15 degrees C had a statistically significant effect on the rate of mineralization and removal of C-14-17 beta-estradiol from the aqueous phase but not for C-14-testosterone or C-14-17 alpha-ethinylestradiol. These results suggest that biosolids in municipal plants in this region have the capability to remove natural steroid hormones in their influents over a range of temperatures but may be less effective at removing the synthetic estrogen 17 alpha-ethinylestradiol.