Fecal indicator bacteria and virus removal in stormwater biofilters : effects of biochar, media saturation, and field conditioning
- Stormwater biofilters are used to attenuate the flow and volume of runoff and reduce pollutant loading to aquatic systems. However, the capacity of such biofilters to remove microbial contaminants remains inconsistent and inadequate. While biochar has demonstrated promise as a media amendment to improve microbial removal in biofilters, it is uncertain if the results are generalizable to the field. To assess biochar performance in a simulated field setting, sand and biochar-amended sand biofilters were periodically dosed with natural stormwater over a 61-week period. The impact of media saturation was assessed by maintaining biofilters with and without a saturated zone. Although biochar-amended biofilters demonstrated improved Escherichia coli removal over sand biofilters early during field conditioning, media type was not significantly associated with E. coli removal after approximately 31 weeks. Presence of a saturated zone was not a significant factor influencing E. coli removal across the entire conditioning phase. Following field conditioning, biofilters underwent challenge tests to assess their capacity to remove wastewater-derived E. coli, enterococci, and male-specific (F+) coliphage. Challenge tests demonstrated enhanced removal of all fecal indicators in biochar-amended biofilters relative to sand biofilters. Additionally, saturated biofilters demonstrated greater removal of fecal indicators than unsaturated biofilters for both media types. Discrepant conclusions from the conditioning phase and challenge tests may be due to variable influent chemistry, dissimilar transport of E. coli indigenous to stormwater and those indigenous to wastewater, and differences in E. coli removal mechanisms between tests. Mobilization tests conducted following the challenge tests showed minimal (< 2.5%) to no observable mobilization of all fecal indicators, regardless of media type and presence of a saturated zone. While our results emphasize the challenge of translating biochar's performance from the laboratory to the field, findings of this study inform biofilter design to remove microbial contaminants from urban stormwater.
|Type of resource
|electronic resource; remote; computer; online resource
|1 online resource.
|Kranner, Benjamin Paul
|Degree committee member
|Stanford University, Civil & Environmental Engineering Department.
|Statement of responsibility
|Benjamin Paul Kranner.
|Submitted to the Civil & Environmental Engineering Department.
|Thesis Engineering Stanford University 2019.
- © 2019 by Benjamin Paul Kranner
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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