ASABE Technical Library - Abstract

Abstract. The loss of phosphorus (P) from agricultural soils to surface waters is recognized as a key contributing factor to eutrophication. High concentrations of P can lead to the development of harmful algal blooms, which present risks to aquatic ecosystems and human health. Recent studies have shown that subsurface drainage can contribute substantially to the loss of dissolved P. It is critical to develop technologies to reduce P concentrations in subsurface drainage to mitigate its environmental impacts. The use of reactive materials to bind P is an emerging technology for P removal from subsurface drainage. The objective of this study was to investigate the P adsorption characteristics of selected natural minerals and industrial byproducts and determine their potential for subsurface drainage P removal.Laboratory batch adsorption experiments were performed to determine the P adsorption capacities of natural minerals and industrial byproducts, including limestone, zeolite, calcite, steel slag, iron filings, and steel byproducts. The steel byproducts included small chips, medium chips, and large turnings, which were collected from local machine shops. Simulated drainage samples were used to evaluate the impact of temperature, reaction time, pH, nitrate, sulfate, and dissolved organic carbon on adsorption of P for the materials.Results showed that iron based industrial byproducts had adsorption capacities that are one order of magnitude higher than natural minerals. Different steel byproducts exhibited P adsorption capacities of 2.5 to 4.5 mg/g, which were comparable to steel slag and iron filings. The P adsorption capacity increased when increasing temperatures from 5 to 30 °C. Steel byproducts exhibited fast P adsorption kinetics as more than 60% of the 24 h adsorption potential occurs within 8 h. Decreasing pH resulted in an increased adsorption capacity among steel byproducts. Nitrate and sulfate had little impact on P removal for steel byproducts while dissolved organic matter inhibited P adsorption by approximately 25%. Overall, the results of this study suggest that steel byproducts are an efficient sorbing material that potentially can be used as adsorption media for P removal from subsurface drainage.