Underground Reactive Barrier to Attenuate Nitrogen, Phosphorus and Other Organic Chemicals from Agricultural Drainage.

The East Tennessee Research and Education Center (ETREC) – Little River Animal and Environmental Unit (LRAEU) is a 529 acre facility with primary research emphasis in its Holstein milking dairy unit.  This site is of potential environmental concern due to the proximity of the Little River, a water body which originates in the Great Smoky Mountains National Park, which serves as a water source for roughly 85,000 throughout its length.  A portion of the Little River is currently categorized as "threatened" on the 2012 EPA 303(d) list of impaired waterways in the state of Tennessee.  The site needs economically feasible on-site water treatment system that is capable of removing excess nutrients (N and P) as well as other natural hormones and feed additives. Previous underground reactive barriers were primarily designed to treat groundwater and not much information about design and efficacy of barriers for treating surface runoff is available.  This is especially true given the unique hydrology (dynamic depth of water table) of the site and limited space.  There is a great need for development of control technology for surface runoff that contains high amount of agricultural chemicals.  A reactive barrier will be proposed to address potential water quality issues associated with the LRAEU with special consideration given to the influence of a variable water table on the system when consistent anaerobic conditions are preferable to treatment process. This study will focus on the hydrological design issues of a biofilter to ensure maximum retention and remediation of contaminated surface water from a dairy pasture. Modeling of various storm events will be used to quantify runoff volume and peak rate.  Using the data an appropriate filter will be sized, and fill materials will be chosen with density, porosity and hydraulic conductivity values most suitable to accommodate waste water removal.  Additional goals will focus on carbon availability of the fill material substrate and increasing bed temperature, two components which previous studies have noted are beneficial in improving nitrate removal performance.