Potential for 17β-estradiol and estrone degradation in a recharge aquifer system

The potential for degradation of two important endocrine disrupting chemicals, 17 beta-estradiol (E2) and estrone (E1) in a wastewater effluent recharged aquifer system was assessed using lab scale microcosms. Biotransformation by microorganisms present in the aquifer material was found to be the major mode of removal for both organic contaminants in the microcosms. The addition of ultrafiltered secondary effluent, simulating recharge of aquifer, did not significantly alter the behavior of both E2 and El in the aquifer microcosms. A significant difference in E2 removal rates in microcosms that received E2 as a concentrated stock in methanol as opposed to direct dissolution of E2 into groundwater shows that the presence of methanol could alter the biodegradation kinetics of the organic pollutant of interest. The rapid utilization of methanol by indigenous methanol degraders, which was present as an alternative carbon substrate, caused rapid depletion of oxygen and, hence, development of anoxic conditions in the microcosms. Increased oxygen supply led to corresponding improved E2 biotransformation rates, indicating that E2 degradation under anoxic conditions was much slower than under aerobic conditions. On the other hand, in the presence of a high initial concentration of methanol, El was more persistent in the medium under aerobic conditions than under anoxic conditions. Apparently, the initial high concentration of methanol had an inhibitory effect on aerobic El degraders in the microcosms.