Fly ash, a byproduct of coal-fueled electrical power plants, has been used to enhance pollutant retention in stormwater filters. Containing significant amounts of the metal oxides CaO, Al2O3, and Fe2O4, fly ash will react with phosphorous to form relativity insoluble minerals, thus reducing the pollutant concentration in the effluent.
Two USEPA-funded projects have designed, constructed, and quantified the long-term performance of fly ash amended filters in 10 bioretention cells in Oklahoma built in 2007. Initial analysis has included RCRA screening, laboratory batch sorption and column experiments, 3-D flow and transport modeling, construction sampling, and field hydraulic testing.
In one of the projects, core and water sampling were carried out after seven years. Core samples were subject to total acid digestion, water extraction, Mehlich 3 extraction, and X-ray absorption near edge structure analysis (XANES). Water sampling was conducted for one year. After the seven-year period had elapsed, phosphorous mass removal was still between 76 and 93 percent, while zinc mass removal was between 43 and 88 percent. In addition, bacteria removal in core columns and effluent was found to be greater than that in sand only filters.
A more recent effort has focused on preprocessing to improve the fly ash handling and design aspects. Results of this work suggest that, with minor qualifications, fly ash should be given strong consideration for expanded use in stormwater filters when phosphorous and/or heavy metals in stormwater are a concern.
Join Forester University for this live, educational webinar as returning speaker Dr. Glenn O. Brown, Regents Professor Emeritus at Oklahoma State University, uses these projects as case studies to illustrate that “the proof is in the pudding” when it comes to the viability of fly ash as a stormwater filter additive.
Interested in previewing Dr. Brown’s work? Be sure to check out his summer 2019 Forester University webinar entitled Stormwater Filter Additives: What Works, What Doesn’t, and What Is Still To Be Learned.
By participating in this webinar, attendees will:
- Gain a basic understanding of fly ash composition and properties
- Know expected fly ash removal efficiencies for phosphorous, heavy metals, and bacteria
- Learn how to design and use fly ash in stormwater filters
- Become aware of potential problems with the use of fly ash
- Receive recommended procedures to measure pollutant(s) retained in any stormwater filter
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