10-2 Effectiveness of Drinking Water Treatment Residual and Zeolite Filter Materials in Phosphate Sorption and Release

Session: Geochemistry and Mineralogy (Posters)

Presenting Author:

Authors:

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 through batch experiments with nanopure water and synthetic rainwater showed very little phosphate desorption after 14 days (<1%). Replication of the desorption experiment 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. While further study is needed to determine if this rate of desorption is validated under field conditions, preliminary data indicates that this filter media is promising for reuse as a slow-release fertilizer. In conclusion, our research confirms the potential for DWTR to efficiently decrease phosphate input to surface waters, explores the mechanisms of sorption, and suggests that the spent material can be used as a slow-release fertilizer to promote a circular economy of phosphorus in agricultural systems. 

Geological Society of America Abstracts with Programs. Vol. 58, No. 2, 2026

© Copyright 2026 The Geological Society of America (GSA), all rights reserved.