Advancing the use of DWTRs in stormwater treatment features to enhance phosphorus removal for transportation projects
Stormwater runoff from urban areas threatens water quality and ecosystems around the world. For freshwater ecosystems, phosphorus (P) is often a primary concern, as excess P loading can cause eutrophication, symptoms of which include harmful algal blooms and oxygen depletion. Dissolved P forms are taken up by primary producers and are therefore a particular concern for water quality. To mitigate these threats, stormwater control measures are often employed to reduce P loading. Sand filters are a type of stormwater management practice that primarily function to trap particulates and thereby reduce downstream sediment and P loads. However, sand filters typically exhibit a negligible capacity to retain dissolved P forms, due to low P sorption capacity of sand. To target both particulate and dissolved P species in stormwater, a P-sorbing material amendment can be added to sand filter media to increase P sorption capacity. This project examined the use of alum-based drinking water treatment residuals (DWTRs), a waste byproduct of drinking water treatment plants, to enhance P removal in sand filter media. The research centered on a field study to determine stormwater P load reductions provided by DWTR-amended sand filters in transportation projects under real-world conditions. Two stormwater sand filters enhanced with DWTRs (3-5% of the sand layer by volume) were monitored from Fall 2022 to Spring 2024 in Chittenden County, Vermont. One filter receives runoff from a small catchment (1.8 acres) at a residential site (A) and the other from a larger catchment (4.5 acres) in an industrial/commercial area (B). The composition of influent stormwater was markedly different between sites, dominated by dissolved P at the residential site, and mostly particulate P at the more industrial/commercial site. Due to this difference in influent water quality, >99% of the total P removed at the residential sand filter was in the form of dissolved P, while only 4% of the total P load removed at the industrial/commercial site was dissolved P. Because removal of dissolved P by sand filters tends to be negligible, the dissolved P load reductions observed at both sites are likely attributable to the DWTRs. Overall, the two systems reduced total P loads by 65-78% during the monitored events. This field study indicates that including DWTRs in sand filter media is an effective way to couple both physical and chemical P removal mechanisms and thereby enhance water quality improvement performance. The researchers provide guidance on future use of DWTRs in stormwater infrastructure based on our findings. The researchers also present stormwater chloride data from the monitored events, which can be used in future efforts to assess road salt effects on stormwater characteristics in Vermont.
Language
- English
Project
- Status: Active
- Funding: $150000
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Contract Numbers:
VTRC022-003
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Sponsor Organizations:
Vermont Agency of Transportation
219 North Main Street
Barre, VT United States 05641 - Start Date: 20220901
- Expected Completion Date: 20240830
- Actual Completion Date: 0
Subject/Index Terms
- TRT Terms: Best practices; Drinking water; Filtration; Phosphorus; Runoff
- Geographic Terms: Vermont
- Subject Areas: Environment; Highways; Hydraulics and Hydrology; Safety and Human Factors;
Filing Info
- Accession Number: 01933024
- Record Type: Research project
- Source Agency: Vermont Agency of Transportation
- Contract Numbers: VTRC022-003
- Files: RIP, STATEDOT
- Created Date: Oct 9 2024 11:48AM