Transformation of Estrogen with Ammonia Oxidizing Bacteria

Understanding estrogen removal mechanisms in wastewater treatment is imperative, as estrogens have environmental impacts at trace concentrations. Research has focused on cometabolic degradation by ammonia oxidizing bacteria (AOB), because greater estrogen removal occurs in treatment plants with nitrification. In this study, no cometabolic degradation was observed in batch tests with Nitrosomonas europaea; LC-MS-MS was employed to measure 17α- ethinylestradiol (EE2) and transformation products. Instead, EE2 was transformed abiotically to nitro-EE2 by reaction with high NO2-N (200–500 mg/L) produced by the AOB. A nitration rate model and first order rate constants for EE2, 17β-estradiol (E2), and estrone (E1) nitration was developed as a function of estrogen, NO2-N, temperature and pH. 90% nitration of the estrogens is achieved at 500 mg/L NO2-N and pH 6.4 over 3.6–4.1 days. Estrogen removal by nitration is not likely in activated sludge of domestic wastewater, but has potential for treatment of high NH4-N strength wastewaters, such as centrate, feedlot wastes and urine.