Resource Magazine — March/April 2014
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The Fate, Transport, and Impact of Estrogens Applied During Wastewater Irrigation
Heather Gall & Herschel Elliott

As concerns about the presence of unregulated compounds known as “emerging contaminants” (ECs) in drinking water sources continue to grow, alternative 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 groundwater aquifers and protect rivers and streams that would otherwise receive discharge from wastewater treatment plants.

Since the 1960s, Penn State University has been applying its treated wastewater to approximately 2.5 km2 (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 conventional 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, excavated, 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 irrigation 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 estrogens. 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 transport pathways in structured soils. Since the water table beneath the Living Filter area is about 50 m below the surface, the likelihood of groundwater contamination by estrogens 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 overlying shallow groundwater.

Assessing the impact on vernal pool ecosystems
Heather Gall and her graduate student, Odette Mina, are interested in understanding the fate of estrogens that are mobilized during surface runoffand their potential threat to nearby aquatic ecosystems. There are several vernal pools near the Living Filter that may be impacted by estrogens and other endocrine-disrupting compounds contained in the irrigated wastewater. Vernal pools are important habitats for amphibians such as frogs and salamanders, which are currently facing global population declines. Although some laboratory studies have been conducted to understand the impact of controlled exposure of amphibians to emerging contaminants, no data exist for the occurrence of the ECs in vernal pools.

Gall, Mina, and their collaborators in Penn State’s Department of Biology (Tracy Langkilde and her graduate student, Bradley Carlson) have identified seven vernal pool sites across an agricultural impact gradient, with the Living Filter sites among those most impacted by agricultural activities. They collected one round of samples in October 2013, when water levels in the pools were low, with the goal of establishing baseline concentrations prior to the pools filling up to normal levels. Of the seven sites, only one had detectable levels of estrogens. That is good news for the tadpoles that are developing at these sites, but the absence of estrogens was expected due to their short half-lives and because no recent stormwater runoffevents had occurred.

These vernal pools receive their water primarily from surface runoffrather than groundwater, and Gall’s team hypothesizes that concentrations will increase following snowmelt and runoffevents, which are expected to transport estrogens, pesticides, and other ECs. Therefore, more water samples will be collected in the winter and spring to assess the impacts of snowmelt and large spring rainfall events on the presence of estrogens in these vernal pools. These data will then be used to develop controlled mesocosm experiments, in which tadpoles are exposed to environmentally relevant “contaminant cocktails.” For more information on Penn State’s Living Filter, visit: eng-resources/living-filter-fact-sheet.

ASABE member Heather Gall, Assistant Professor,, and Herschel Elliott, Professor,, Department of Agricultural and Biological Engineering, Pennsylvania State University, University Park, USA.