Potential of Phosphate-Capturing Filter Media for Reuse as Slow-Release Fertilizer
Papazoglou, Annie
Papazoglou, Annie
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Abstract
Phosphate-rich agricultural runoff contributes to harmful algal blooms in bodies of water across the Northeastern United States, including Lake Champlain. To mitigate harm to local wildlife, recreation, and tourism, the EPA has implemented a total maximum daily load of phosphates entering the lake, stimulating demand for methods of phosphate removal from runoff. We used solid byproducts of the water treatment process (Drinking Water Treatment Residuals - DWTR), combined with zeolites to selectively bind phosphates in an end-of-tile filter within an agricultural context. With a previously determined maximum sorption capacity of 18.2 mg/g phosphate, we quantified the rate at which the captured phosphate is desorbed from this material. Our goal is to inform the potential for its reuse as a slow-release fertilizer. Characterization of the solid filter media pre- and post-sorption by XRF, XRD, FTIR and SEM suggested outer-sphere complexation of phosphate with aluminum-rich DWTR moieties. Post-sorption, we subjected the spent filter material to column and batch experiments designed to mimic field release. Initial analysis in batch experiments in reacted with nanopure water and synthetic rainwater showed very little phosphate desorption after 14 days (<1%). Replication of the desorption in dynamic flow-through columns is expected to cause higher desorption rates as models indicate that increased competition and ion kinetics would displace phosphates from binding sites more effectively. In the context of fertilizer shortage, our experiments suggest that the filter media is effective at capturing, storing, and releasing phosphate at slow rates. This research confirms the potential for DWTR to efficiently decrease PO4 input to surface waters, explores the mechanisms of sorption and suggests that the spent material can be used as a slow-release fertilizer, promoting a circular economy of phosphorus in agricultural systems.
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Date
1/1/2026
Student Status
Junior (Graduating in 2027)
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Poster
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Chemistry
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College of Arts and Sciences
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Physical Science