Location: National Soil Erosion ResearchTitle: Phosphorus retention by fly-ash amended filter media in aged bioretention cells
|KANDEL, S - Oklahoma State University|
|VOGEL, J - University Of Oklahoma|
|BROWN, G - Oklahoma State University|
Submitted to: Water
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/27/2017
Publication Date: 9/29/2017
Citation: Kandel, S., Vogel, J., Penn, C.J., Brown, G. 2017. Phosphorus retention by fly-ash amended filter media in aged bioretention cells. Water. 9:746. doi:10.3390/w9100746.
Interpretive Summary: Excess phosphorus (P) transported to surface waters from the landscape is a significant contributor to eutrophication and poor water quality. Bioretention cells (BRC) are an urban best management practice (BMP) that work by mitigating both water quantity and quality through slow release of runoff water and filtering of nutrients such as P. A new technique for BRCs includes use of fly-ash as a P filter material, thereby making the BRC a type of P removal structure. This study examined the effectiveness of several BRCs that were in operation for several years. The filter media was sampled to a depth of 0.6 m and tested for different forms of P. Most of the P was captured in the upper 15 cm of the BRCs. Overall efficiency of the BRCs with fly-ash ranged from 68-75% in reducing P concentration, and 76-93% in reducing P mass (i.e. load). The research findings are useful to those who are interested in building P removal structures to mitigate excessive P in drainage waters.
Technical Abstract: Bioretention cells (BRCs) have shown potential for stormwater quantity and quality control. However, the phosphorus (P) removal in BRC has been variable due to differences of soil properties in filter media. The objectives of this research were to identify and evaluate P accumulation in filter media and to quantify effluent P reduction in BRC. Each cell has a sand and fly-ash media designed to remove phosphorus. Filter media were collected in 2014 across the cell surface and to a depth of 0.6 m to quantify the P accumulation. The mean total P (T-P) concentration increased over the seven years of operation, but the changes were not statistically significant. The average Mehlich-3 P (M3-P) and water soluble P (WS-P) concentrations in the media profiles showed higher P accumulation in the top 0.15 m. The average M3-P and WS-P concentrations between 0.15 to 0.30 m, and 0.30 to 0.60 m were variable on all four BRCs media. The media with 5% fly ash significantly retained M3-P and WS-P over the top 0.15 m. Stormwater influent and effluent samples from three of the BRCs monitored over one year showed reductions in both P concentration (68% to 75%) and P mass (76% to 93%).