Abstract
Phosphorus (P) transported in runoff from broiler production areas is a potential source for nutrient enrichment of local surface waters. Capturing nutrients prior to runoff leaving the production area could reduce the risk of transport. Commercially available systems for nitrogen (N) and P removal from stormwater are available but too expensive for widespread adoption on small, privately owned farms. The P adsorption capacities and hydraulic conductivities of locally-sourced iron red mud (RM) and aluminum water treatment residual (WT) were determined for potential on-farm treatment use. The byproducts were air-dried and separated into ≤2-, ≤6-, and ≤12.5-mm particle size fractions. Saturated hydraulic conductivity (HC) was determined for each particle-size fraction and results evaluated for the material’s ability to transmit a 25-year, 30-min rainfall of 6.6 cm. While the HC of ≤6-mm particles of each byproduct did not differ (p > 0.05; 4.1 and 4.6 cm·min-1), for ≤12.5-mm particles it was greater (p > 0.05) for WT than RM (15.4 and 8.0 cm·min-1, respectively). However, all byproduct size fractions transmitted flow sufficiently to accommodate the baseline storm. Phosphorous adsorption maxima of ≤2-mm fraction for RM and WT were 25 and 10 g·P·kg-1, respectively. Using a solution containing 6 mg·P·L-1, rep-resenting the measured runoff-P concentration from areas adjacent to poultry house ventilation fans, the ≤2-mm fraction of RM removed 98% of added P and WT 84%. The ≤6-mm fraction of RM and WT removed 56% and 57% of added P, respectively, while the ≤12.5-mm fraction adsorbed only 28% and 10%. Results indicate the potential use of low-cost RM and WT byproducts to sequester P in runoff prior to P leaving poultry farm production areas.
Highlights
Water quality impairment from phosphorus (P) enrichment is a major concern in many areas of the U.S, with agriculture purported to be a major contributor [1] [2]
The Phosphorus adsorption maxima (Pmax) value for red mud (RM) was greater than 87% of the materials listed and that for water treatment residual (WT) was greater than 74% of those listed
The Pmax values for RM and WT were compared with other P adsorbents that have been evaluated, and the Pmax value for RM was greater than 87% of the materials evaluated, and that for WT was greater than 74% of those evaluated
Summary
Water quality impairment from phosphorus (P) enrichment is a major concern in many areas of the U.S, with agriculture purported to be a major contributor [1] [2]. Runoff from the land directly around broiler production facilities has been shown to be enriched with nutrients that could potentially contribute to nearby surface water quality impairment [3] [4]. Removing P from runoff water prior to it leaving the production area is more cost-effective than treating the receiving water once impaired [5]. While P can be removed during movement along a grassed waterway between poultry houses, P can accumulate in the soil, which can represent a long-term source of P for off-site transport in runoff [6]. Conservation practices that trap P prior to the P leaving the production area are needed for protection of surface water quality
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