Vegetative Treatment Systems as Alternative Treatment Options for Livestock Farms
Vegetative Treatment Systems can be useful low-tech solutions as Alternative Treatment Options providing manure treatment for livestock farms, particularly for areas of intensive farming, known as CAFOs in US terminology.
A CAFO is defined as a concentrated animal feeding operation CAFOs are agricultural facilities that house and feed a large number of animals in a confined area for 45 days or more during any 12-month period.
Introduction to Vegetative Treatment Systems
For small and medium animal feeding operations, vegetative treatment systems (VTS) may provide an option for avoiding classification as a CAFOs.
For large CAFOs, VTS may provide an option for meeting the effluent limitation guidelines (ELGs) of the CAFO regulations.
This section reviews the ELGs for CAFOs and the performance requirements that a VTS must meet as an alternative technology.
Vegetated Treatment Areas
Vegetated Treatment Areas (VTAs) are generally regarded as an alternative technology that alone will not meet the Effluent Limitation Guidelines of the CAFO regulations.
This section will review several system options that include a VTA for their potential application to CAFOs. via water.unl.edu
Environmental “Good Neighbour” Uses of VTAs
Vegetative Treatment Areas (VTA) typically offer significant value to siting of a runoff management system within a rural neighbourhood.
These systems replace a large holding pond with natural grasslands or forage production areas providing advantages for wildlife, odours and other gaseous emissions, and visual appearances of the livestock system.
However, space requirements as well as connections to surface and groundwater must be considered for avoiding higher risk environmental concerns.
The liquid-solid separation component is a key feature of a VTA System. This component should:
- Remove most settable solids from feedlot runoff and
- Release liquids to VTA or IB in a controlled manner to minimize the potential for discharge.
This next section will discuss the design features of the liquid-solid component critical to achieving those goals.
Vegetative Treatment Systems Definition
Runoff from livestock barnyards and feedlots can kill fish and cause algae blooms in lakes and streams. A Vegetative Treatment System (VTS) can be an economical alternative to retention (holding) ponds for controlling runoff from a livestock waste facility.
A Vegetative Treatment System (VTS) refers to a combination of treatment steps for managing runoff. It treats runoff by settling, infiltration, and nutrient use. Individual components of a VTS include, a settling structure, an outlet structure, a distribution system, and a Vegetative Treatment Area, when put together we consider it a Vegetative Treatment System. via water.unl.edu
Vegetative Treatment Area Management
A Vegetative Treatment Area (VTA) is an area of perennial vegetation, such as a grass or a forage. The VTA is used to treat runoff from a feedlot or barnyard.
It treats runoff by settling, infiltration, and nutrient use. A VTA is commonly confused with vegetative buffer (or filter) strips.
The Buffer Strip
A buffer strip is a narrow strip of vegetation (usually 30-60 feet wide), between cropland and a stream or other surface water. Runoff passes through buffers with some “filtering” of pollutants, but no attempt is made to control solids or flow.
A VTS, however, collects runoff from a barnyard or feedlot, separates the solids from the liquids, and uniformly distributes the liquid over the vegetated area. Little or no runoff should leave a VTA.
The first step in a VTS is to collect runoff from a open lot or barnyard area in a sediment settling structure, usually a basin. Such basins are very effective for removing most solids. The runoff then flows into a VTA (Vegetative Treatment Area) whose soil treats and stores the runoff. Once the runoff is in the soil, natural processes allow plants to use the nutrients. lpelc.org
At the next point in a VTS design, there are 3 options for the type of VTA to be used:
The 3 Basic Types of VTA
1. Sloped Vegetative Treatment Area (VTA)
Sloped VTA refers to a treatment area that is slightly sloped. The slope allows liquid to uniformly spread across the width of the treatment area and flow the length of the VTA. Sloped VTAs should be between 0.5 percent to 6 percent downslope and should be level from side to side. Borders, berms, furrows, and cross ditches can be used to maintain uniform flow. If the site is near a receiving water and the potential for frequent discharge exists, a Vegetative Infiltration Basin (VIB) is required. A VIB is a temporary storage area to allow soils and plants to absorb and utilize the excess water exiting the end of the sloped VTA.
2. Terrace VTA
Terrace VTAs are terraced channels used to contain and treat runoff on fields with steep slopes. They must be fairly large and well-maintained, and should be planted to grass. Two types of terrace systems exist:
- (1) a flow through terrace system that acts similar to a sloped VTA, and
- (2) a flat channel storage terrace (water storage) similar to a VIB. Terraces used to control erosion in crop fields should not be used as a VTA without modification.
3. Sprinkler VTA
Sprinkler VTA is an area of perennial vegetation with runoff distributed by a sprinkler irrigation system. A solid set sprinkler, tow line, or side roll can be used to distribute the runoff collected in a settling basin.
Although more expensive than a gravity VTA, a sprinkler VTA provides uniform application of runoff and nutrients. They are applicable to situations where a gravity system is not feasible, and can be used with any soil texture. An all-weather pumping station is required for a sprinkler VTA. via www.nrcs.usda.gov
Case Study of VTA in Use
The performance of six vegetative treatment systems on open beef feedlots throughout Iowa was monitored from 2006 through 2009.
These feedlots had interim, National Pollution Discharge Elimination System permits that allowed the use of vegetative treatment systems to control and treat runoff from the open feedlots.
The report focuses on making within-site comparisons, i.e., from year-to-year and component-to-component within a site, to evaluate how management changes and system modifications altered performance.
The effectiveness, in terms of effluent concentration reductions, of each system was evaluated.
Nutrient concentration reductions were reported to typically range from 60 to 99% during treatment in the vegetative components of the vegetative treatment systems monitored. via NCBI