Occurrence, Fate, and Transport of Estrogenic Compounds in the Mixing Zone of Shallow Receiving Waters

Estrogens are the primary source of estrogenic activity in wastewater effluents. When discharged, estrogen-laden effluents impart estrogenicity to the receiving water thus impacting aquatic organisms. This research investigated the existence, severity, and attenuation of estrogenicity in the mixing zone of a shallow receiving water. A simple analytical mass transport model was developed and implemented to simulate the transport of estrogens in Moore's Creek, a small stream receiving effluent from a domestic wastewater treatment plant (WWTP) in Charlottesville, VA.;Four environmental estrogens, namely, 17beta-estradiol, estrone, estriol, and bisphenol-A, and two pharmaceuticals, acetaminophen and triclosan, were detected in the water samples collected from the Creek. Concentration measurements indicated that the effluent was the primary source of estrogenicity in the mixing zone of the Creek. This was further supported by results from an in vitro estrogenicity assay of water samples collected from the Creek and from the WWTP effluent. Estrogenic activity in the Creek was largely attributed to the 17beta-estradiol and was higher than ambient values near the effluent bank. Measured estrogenicity in the Creek downstream of the outfall exceeded reported levels severely toxic for vitellogenin induction in male fathead minnows (100 ng/L).;An analysis of the stream flow properties and estrogen mass transport coefficients in Moore's Creek indicated that 17beta-estradiol is degraded quite slowly as it is transported downstream from the outfall. Dilution by mixing was also found to be the primary attenuation mechanism for the estrogenicity in the mixing zone. Further, sediment sorption may have minimal contribution to attenuation of estrogenicity in this Creek due to the limited availability of sediments in the channel bed.;The dilution and dispersion of estrogens in a shallow mixing zone was found to be influenced mostly by the WWTP discharge. Increased estrogen loads in the effluent increase the severity of estrogenicity in the receiving water, while higher effluent flows extend the spread of the mixing zone. Thus, strategies for reducing estrogenicity in shallow receiving waters can be based on regulating these two factors: either by improving estrogen removal in the WWTP or staging effluent flow releases so that the beneficial effects of dilution in the receiving stream can be optimized.