The Fate, Transport, and Impact of Estrogens Applied During Wastewater Irrigation Heather Gall and Herschel Elliott A s concerns about the presence of unregulated com-pounds known as “emerging contaminants” (ECs) in drinking water sources continue to grow, alter-native solutions for managing wastewater are becoming increasingly appealing. Irrigation with wastewater is commonly used for agriculture in developing countries. In contrast, land application of treated wastewater is being used in the United States as a way to artificially recharge ground-water aquifers and protect rivers and streams that would oth-erwise receive discharge from wastewater treatment plants. Since the 1960s, Penn State University has been applying its treated wastewater to approximately 2.5 km 2 (600 acres) of agricultural and forested land, known as the Living Filter. This provides a great benefit to Spring Creek’s water quality, which had previously received effluent from the university’s wastewater treatment plant. However, more than 50 years later, it is now recognized that ECs, many of which are known endocrine disruptors, are not completely removed in conven-tional wastewater treatment and thus are being inadvertently introduced into the environment during this irrigation. Two research groups in Penn State’s Department of Agricultural and Biological Engineering are trying to understand the fate, transport, and threats of estrogens contained in the irrigated wastewater. Understanding the threat to groundwater Herschel Elliott and his graduate student, Senorpe Asem-Hiablie, recently completed an assessment of the potential for estrogens to reach the aquifer beneath the Living Filter. To study undisturbed soil profiles, cube-shaped steel casings (60 cm on a side) were driven into the ground, exca-vated, and used as lysimeters to evaluate the vertical transport of three estrogens. Effluent spiked with the estrogens and an inert tracer was applied to the lysimeters at the actual irriga-4 March/April 2014 RESOURCE tion rate (5 cm per week), and the leachate was monitored for six months. Leachate estrogen levels were generally less than 10% of the applied concentrations, suggesting that sorption to soils significantly retards subsurface transport of estro-gens. However, rapid appearance of estrogens in the leachate after application of less than one pore volume of effluent implies that the soil macropores serve as preferential trans-port pathways in structured soils. Since the water table beneath the Living Filter area is about 50 m below the sur-face, the likelihood of groundwater contamination by estro-gens is low at this site. However, the impact of surface irrigation-applied estrogens on water quality may be greater for areas with coarse-textured or highly structured soils over-lying shallow groundwater. Senorpe Asem-Hiablie prepares an undisturbed soil lysimeter.