Thesis
Assessment of water quality and a vegetative filter strip on a central Washington irrigation ditch using enumeration of bacterial indicator organisms and detection of foodborne pathogens
Washington State University
Master of Science (MS), Washington State University
2015
Handle:
https://hdl.handle.net/2376/100867
Abstract
With recent produce outbreaks linked to contaminated water, understanding agricultural management practices to enhance water quality is important. A two year study assessed water quality in an irrigation ditch and soil microbial levels in a vegetative filter strip near a cattle feedlot. Fourteen water sampling sites were selected. Two transects of a vegetative filter strip (East and Middle) were sampled at 3 locations each and at two depths (surface and 10cm). Sampling periods (13 total) occurred between April-November 2008 and 2009. Water and soil were quantified for total and fecal coliforms as well as generic E. coli using a five-tube most probable number technique. Both the Washington Department of Ecology (WADOE) and Leafy Greens Marketing Agreement (LGMA) utilize a rolling geometric mean (RGM) and single sample standard for fecal coliforms and generic E. coli, respectively. The Food Safety Modernization Act proposed produce rule utilized a generic E. coli GM, and a statistical threshold value. All 14 sites failed the WADOE standard in both years. Lower generic E. coli levels in 2009 influenced compliance. In 2008, 1.8% (1 of 56) of sampling sites met the LGMA foliar application and 8.9% (5 of 56) met the LGMA non-foliar application standards. In 2009, 85.7% (12 of 14) sampling sites met for foliar application and 100% (14 of 14) met for non-foliar application. In 2008, 7.1% (1 of 14) of sites met the FSMA generic E. coli standard and 100% (14 of 14) met in 2009. Sampling date significantly influenced indicator organism levels in soil and transect within the vegetative filter strip influenced total coliforms and generic E. coli. Prevalence rates of Salmonella were 3.0% (10 of 338), with 4.9% (9 of 182) in water and 0.6% (1 of 156) in soil. Prevalence rates of E. coli O157:H7 were 0.3% (1 of 338), with 0.5% (1 of 182) in water and none detected (0 of 156) in soil. The type of indicator organism selected and standard utilized has significant ramifications on evaluation of bacterial water quality. Soil indicator organism levels within a vegetative filter strip can vary greatly depending on sampling location and date.
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Details
- Title
- Assessment of water quality and a vegetative filter strip on a central Washington irrigation ditch using enumeration of bacterial indicator organisms and detection of foodborne pathogens
- Creators
- Sean Michael Beckman
- Contributors
- Karen Killinger (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Food Science, School of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; [Pullman, Washington] :
- Identifiers
- 99900525400501842
- Language
- English
- Resource Type
- Thesis