Vegetated treatment area effectiveness at reducing nutrient runoff from small swine operations in central Texas

Authors: Higgs, Kori; Harmel, Daren; WAGNER, K - Texas Water Resources Institute; SMITH, P - Texas A&M University; Haney, Richard; Smith, Douglas; PAMPELL, REHANON - Texas Agrilife Research

Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/23/2015
Publication Date: 8/1/2015
Publication URL: http://handle.nal.usda.gov/10113/61274
Citation: Higgs, K.D., Harmel, R.D., Wagner, K., Smith, P.K., Haney, R.L., Smith, D.R., Pampell, R. 2015. Vegetated treatment area effectiveness at reducing nutrient runoff from small swine operations in central Texas. Applied Engineering in Agriculture. 31(4):621-629.

Interpretive Summary: Numerous modeling and field studies have evaluated the effectiveness of vegetative treatment systems in treating runoff from animal feeding operations; however, none have evaluated the effectiveness of vegetative treatment areas (VTA’s) receiving direct runoff from small swine operations during natural rainfall events. This project aims to determine whether a sufficiently sized VTA alone can effectively treat direct runoff from such operations. Three locations were established in 2012, and sampling sites were installed to measure runoff water quantity and quality at the VTA inlet and outlet and a nearby control area. The VTA’s reduced runoff volume by 17-55% and provided substantial treatment of the swine facility runoff reducing nutrient concentrations by 23-91% and loads by 50-96%, although some nitrogen concentrations and loads increased. The Bell county VTA operated as “desired” because VTA outlet loads as well as ammonium nitrogen and total phosphorus concentrations were significantly lower than the VTA inlet and were not significantly different than the control; however, nitrate nitrogen, soluble phosphorus, and total nitrogen concentrations remained higher than the control. The Brazos county VTA also significantly reduced all nutrient concentrations and loads, but the reductions were not adequate to match levels at the control partly due to low runoff volume at the control and resulting low nutrient loads. The Robertson county VTA inlet and outlet produced low nutrient concentrations and loads that were similar to the control. The positive water quality results at this location are attributed partly to alternative management of solids and the enclosed barn pens not entirely to VTA effectiveness. Average soil nitrogen and phosphorus levels decreased from April 2013 to October 2014, although some nutrient build-up did occur at the Bell and Brazos county VTA’s but only in the upper end. This study highlighted the importance of solids management, maintenance of perennial grasses and subsequent haying and removal, and consideration of nutrient loads relative to VTA area. Based on these results, VTA’s can be a practical, cost-effective, environmentally-friendly wastewater management alternative with proper consideration of these design and management factors.

Technical Abstract: Numerous modeling and field studies have evaluated the effectiveness of vegetative treatment systems in treating runoff from animal feeding operations; however, none have evaluated the effectiveness of vegetative treatment areas (VTA’s) receiving direct runoff from small swine operations during natural rainfall events. This project aims to determine whether a sufficiently sized VTA alone can effectively treat direct runoff from such operations. Three locations were established in 2012, and sampling sites were installed to measure runoff water quantity and quality at the VTA inlet and outlet and a nearby control area. The VTA’s reduced runoff volume by 17-55% and provided substantial treatment of the swine facility runoff reducing nutrient concentrations by 23-91% and loads by 50-96%, although some median NO3-N concentrations and loads increased. The Bell county VTA operated as “desired” because VTA outlet loads as well as NH4-N and total P concentrations were significantly lower than the VTA inlet and were not significantly different than the control; however, NO3-N, PO4-P, and total N concentrations remained higher than the control. The Brazos county VTA also significantly reduced all nutrient concentrations and loads, but the reductions were not adequate to match levels at the control partly due to low runoff volume at the control and resulting low nutrient loads. The Robertson county VTA inlet and outlet produced low nutrient concentrations and loads that were similar to the control. The positive water quality results at this location are attributed partly to alternative management of solids and the enclosed barn pens not entirely to VTA effectiveness. Average soil N and P levels decreased from April 2013 to October 2014, although some nutrient build-up did occur at the Bell and Brazos county VTA’s but only in the upper end. This study highlighted the importance of solids management, maintenance of perennial grasses and subsequent haying and removal, and consideration of nutrient loads relative to VTA area. Based on these results, VTA’s can be a practical, cost-effective, environmentally-friendly wastewater management alternative with proper consideration of these design and management factors.