FATE AND TRANSPORT OF MANURE-BORNE PATHOGENIC MICROORGANISMS
Title: Uncertainty Evaluation of Coliform Bacteria Removal from Vegetated Filter Strip under Overland Flow Condition
Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 6, 2009
Publication Date: July 1, 2009
Citation: Guber, A.K., Yakirevich, A.M., Sadeghi, A.M., Pachepsky, Y.A., Shelton, D.R. 2009. Uncertainty Evaluation of Coliform Bacteria Removal from Vegetated Filter Strip under Overland Flow Condition. Journal of Environmental Quality. 38:1636-1644.
Interpretive Summary: Fecal contamination of surface water resources is a critical water quality issue, leading to many documented health and environmental concerns. Vegetative filter strips (VFS) are proved to be one of the more effective management practices in reducing the level of pollutions before reaching surface water resources. A relatively simple overland flow and transport model was developed and shown to be reasonably successful in explaining the observed experimental data on manure-borne bacteria transport collected at the Beltsville lysimeter site on vegetated plots that emulated actual vegetated filter strips. The vegetated filter strip (vfs) efficiency was found to be less than 95% in 25% of cases, less than 75% in 23% of cases, and less than 25% in 20% of cases. Overall, our results indicated that relatively long high-intensity rainfalls, low hydraulic conductivities, low net capillary drive of soil, and high soil moisture contents before the rainfall, were the main sources of the VFS low efficiency.
Vegetated filter strips (VFS) have become an important component of water quality improvement by reducing sediment and nutrients transport to surface water. This management practice is also beneficial for controlling manure-borne pathogen transport to surface water. The objective of this work was to assess the VFS efficiency and evaluate the uncertainty in predicting the microbial pollutant removal from the overland flow in VFS. We used the kinematic wave overland flow model as implemented in KINEROS2 coupled with the convective-dispersive overland transport model which accounts for the reversible attachment-detachment and surface straining of infiltrating bacteria. The model was successfully calibrated with experimental data obtained from a series of simulated rainfall experiments at vegetated and bare sandy loam and clay loam plots, where fecal coliforms were released from manure slurry applied on the top of the plots. The calibrated model was then used to assess the sensitivity of the VFS efficiency to the model parameters, rainfall duration and intensity for a case study with a 6-m VFS placed at the edge of 200-m long field. The Monte Carlo simulations were also carried out to evaluate the uncertainty associated with the VFS efficiency given the uncertainty in the model parameters and key inputs. The VFS efficiency was found to be less than 95% in 25%, less than 75% in 23%, and less than 25% in 20% of cases. Relatively long high-intensity rainfalls, low hydraulic conductivities, low net capillary drives of soils, and high soil moisture contents before rainfalls, caused the partial failure of VFS.