|Faucette, L. Britt|
Submitted to: Journal of Soil and Water Conservation Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/4/2008
Publication Date: 7/1/2008
Citation: Faucette, L.B., Sefton, K.A., Sadeghi, A.M., Rowland, R.A 2008. Sediment and phosphorous removal from simulated storm runoff with compost filter socks and silt fence. Journal of Soil and Water Conservation Society. 63:257-264. Interpretive Summary: Compost Filter Socks are a relatively new device used in various applications to reduce sediment and pollutant loads from runoff into surface water resources. The compost filter socks are often being used in place of the industry-standard silt fence for these applications. The goal of this study was to compare the flow through and sediment reduction capabilities of these new devices with the traditional silt fence under identical experimental conditions. In addition, we also determined if the addition of polymers to the material within these compost filter socks could further reduce sediment and phosphorous loads, compared to the same silt fence. A series of laboratory studies were conducted on relatively large soil chambers with 10% slope, using simulated rainfall. In addition to the measurement of hydraulic flow rate and volume for each experimental run, runoff samples were also analyzed for various sediment size losses, runoff water turbidity, and phosphorous, ammonia, and nitrate concentrations.
Technical Abstract: In 2005, the US EPA National Menu of BMPs for Storm Water Phase II listed compost filter socks as an approved BMP for controlling storm runoff on construction sites (US EPA, 2006). Like most new technologies used to control sediment on construction sites, little has been done to evaluate their performance relative to conventional sediment control devices, such as silt fence. The objectives of this study were, i) to determine and compare the sediment removal efficiency of silt fence and compost filter socks under the same test conditions; ii) to determine if the addition of polymers to compost filter socks could reduce pollutant loads relative to silt fence; iii) to determine hydraulic flow rate for compost filter socks and silt fence; iv) to determine support practice factors (P Factor) as defined by the RUSLE; and, v) to determine relationships between compost sock particle size distribution and pollutant removal efficiency and hydraulic flow rate. Simulated rainfall was applied to soil chambers packed with Hatboro silt loam on a 10% slope. All runoff was collected and analyzed for hydraulic flow rate, volume, TSS concentration and load, TS concentration, turbidity, total and soluble P concentration and load, and ammonia-N and nitrite-nitrate-N concentration. Based on 30 min. of simulated rainfall with intensities between 5.41 and 9.19 cm/hr generating bare soil (control) TSS-laden runoff loads were between 606 and 823 g, TSS concentrations were between 49 and 70 mg/L, and turbidity between 19343 and 36688 NTUs. Compost filter sock and silt fence removal efficiencies for TSS concentration and load, and turbidity were nearly identical; however with the addition of flocculants to the compost filter socks sediment removal efficiencies ranged from 91 to 99%. Similarly, total and soluble P concentration and load removal efficiencies were similar for silt fence and compost filter socks; although when flocculants were added to the filter socks and installed on phosphorus fertilized soils removal efficiencies were increased to 92 to 99%. Significant correlations were found between middle range particle sizes of compost used in the filter socks and reduction of turbidity in runoff; however, hydraulic flow rate is a better indicator of pollutant removal efficiency performance for compost filter socks and should be considered as a component for inclusion into standard specifications for these sediment and pollution control technologies.