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Separation of Phosphorous- and Nitrogen Nutrients from Agriculturally Degraded Waters Using Previous Filter Material Developed from Industrial By-products

Separation of Phosphorous- and Nitrogen Nutrients from Agriculturally Degraded Waters Using Previous Filter Material Developed from Industrial By-products

Dr. Chin-Min Cheng, a Senior Research Engineer in the Department of Civil, Environmental, and Geodetic Engineering at Ohio State University, and collaborator Dr. Linda Weavers completed an Ohio WRC funded project titled “Separation of Phosphorous- and Nitrogen Nutrients from Agriculturally Degraded Waters Using Previous Filter Material Developed from Industrial By-products”. The goal of the project was to demonstrate the feasibility of applying a low-cost and environmentally-sustainable approach to agriculture drainage water (ADW) handling and treatment. Excessive releases of phosphorous (P) and nitrogen (N) from soil to drainages is a leading cause of harmful algal blooms and eutrophication in water bodies. While many best management practices focus on source reduction and minimizing transport, these methods have not proven to prevent dissolved phosphorous loss, which is the form most readily available to aquatic organisms. Instead, drain-end filtration has been suggested as a better approach, although ideal filter materials have yet to be identified.


In this project, two specific pervious materials were tested: P-type (composed of fly ash, stabilized flue gas desulfurization (FGD), and quick lime) and N-type (composed of fly ash, FGD, and red mud). One column test was a closed-loop test to simulate the removal of phosphate and nitrates when passing ADW through an unlimited length of pervious sorbent column. It was found that the concentration of nitrate in the in the first series decreased over 68.5% after 30 hours of circulation (Figure 1). In the second series, a removal efficiency of 60.1% was observed during the first 26 hours when only N-type column was used. For phosphate, over 95% of the phosphate in the solution was removed within 30 hours of circulation (Figure 2). These results indicate that the pervious materials used in this study can effectively decrease the concentration of nitrate and phosphate.

Figure 1. Temporal trend of nitrate in the closed-loop column systemFigure 2. Temporal Trend of phosphate in the closed-loop column system

Additionally, a flow-through column test was setup to further assess the removal of nitrate and phosphate. The results showed over 77% of nitrate removal was achieved after one pore volume passing through the column, and increased to 98% after 168 hours (Figure 3). For phosphate, over 99% of removal was achieved after 28 pore volumes, an increase from the 82.5% observed after one pore volume (Figure 4). Results obtained from the flow through column test confirmed the potential of using pervious material derived from stabilized FGD material (P-type) to remove both nitrate and phosphate from agricultural drains.

Figure 3. Removal efficiency of nitrate using the P-type pervious material with a flow through columnFigure 4. Removal efficiency of phosphate using the P-type pervious material with a flow through column