Location: National Soil Erosion ResearchTitle: Performance of a ditch-style phosphorus removal structure for treating agricultural drainage water with aluminum-treated steel slag
|SHEDEKAR, VINAYAK - The Ohio State University|
|PEASE, LINDSAY - University Of Minnesota|
|KALCIC, MARGARET - The Ohio State University|
Submitted to: Water
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/24/2020
Publication Date: 7/30/2020
Citation: Shedekar, V., Penn, C.J., Pease, L., King, K.W., Kalcic, M., Livingston, S.J. 2020. Performance of a ditch-style phosphorus removal structure for treating agricultural drainage water with aluminum-treated steel slag. Water. 12(8). Article 2149. https://doi.org/10.3390/w12082149.
Interpretive Summary: Dissolved phosphorus (P) losses to surface waters are considered the main cause of surface water eutrophication, such as Lake Erie. Phosphorus removal structures are large landscape-scale filters for trapping dissolved P in non-point drainage before reaching surface waters. This was the first study that examined the ability of an Al-coated steel slag in removing dissolved P from tile drainage water.The P removal structure consisted of ~ 50 tons Al-coated slag. While the structure was somewhat improperly constructed, with problems in slag coating process and use of excessive particle size, it still removed around 30% of the 16-month dissolved P load. The structure also removed a tremendous mass of sediment and therefore total P (50% of total P for 9.4 kg removed). This study showed that laboratory flow cells agreed well with field data, when normalized for P loading. Also, Al-coated slag is effective at treating dissolved P from tile drains, whereas regular slag is poorly effective.
Technical Abstract: Several structural, treatment, and management approaches exist to minimize phosphorus (P) transport from agricultural landscapes (e.g., cover cropping and conservation tillage). However, many of these practices are designed to minimize particulate P transport and are not as effective in controlling dissolved P (DP) losses. Phosphorus removal structures employ a P sorption material to trap DP from flowing water. These structures have been successful in treating surface runoff by utilizing aluminum (Al)-treated steel slag, but subsurface tile drainage has never been tested with this material. The goal of this study was to evaluate the performance and economics of a ditch-style P removal structure using Al-treated steel slag for treating agricultural subsurface drainage discharge. The structure treated subsurface drainage water from a 4.5 ha agricultural field with elevated soil test P levels. Overall, the structure removed approximately 27% and 50% of all DP and TP entering the structure, respectively (i.e., 2.4 and 9.4 kg DP and TP removal). After an initial period of strong DP removal, the discrete DP removal became highly variable. Flow-through analysis of slag samples showed that the slag used to construct the structure was coarser and less sorptive compared to the slag samples collected prior to construction that were used to design and size the structure. Results of this study highlight the importance of correctly designing the P removal structure using representative PSMs.