Improving runoff water quality from small pork production facilities using vegetative treatment areas
K. Wagner, R. Pampell, D. Hrmel
The U.S. Department of Agriculture–Agricultural Research Service (ARS) and Texas Water Resources Institute (TWRI) initiated this project with funding from the TSSWCB to evaluate an alternative manure treatment system, a vegetated treatment area (VTA), to treat runoff and wash water from small pork production facilities. This evaluation was designed to provide the scientific basis for considering this system for inclusion as an approved practice in the WQMP Program.
The demonstration and evaluation of the VTA system was initiated at three small pork production facilities in Bell, Brazos, and Robertson Counties. Water quality monitoring stations were established at: 1) adjacent control sites, 2) below pens and barns to quantify water quality leaving the facility prior to treatment in the VTA, and 3) at the VTA outlet to quantify effectiveness of the VTA in treating runoff. Runoff volume and event mean concentrations for E. coli, nitrogen (N), and phosphorus (P) were determined for each rainfall runoff event. Soil sampling was also conducted to assess nutrient accumulation and movement within the VTAs.
This 4-year evaluation found that VTAs reduced runoff volume by up to 29%, total N concentrations 47-76%, total P concentrations 65-88%, and E. coli concentrations 34-93%. Additionally, nutrient loads were reduced by 32-92%, and E. coli loads were reduced by 29-94%. Despite these reductions, with the exception of Robertson County, runoff from the VTAs had higher concentrations than control sites. This is attributed to alternative management of solids (i.e. solids removal) and enclosed barn pens used at the Robertson County site.
Based on evaluation results, VTAs were found to be a practical, environmentally-friendly waste management alternative for reducing nutrient and bacteria concentrations and loading from small pork production operations if proper consideration is given to design and management factors (e.g., solids management, perennial grass cover and subsequent haying and removal, and nutrient loads/VTA area).