The use of rapid, small-scale column tests to determine the efficiency of bauxite residue as a low-cost adsorbent in the removal of dissolved reactive phosphorus from agricultural waters.

Bauxite residue, the by-product produced in the alumina industry, is a potential low-cost adsorbent in the removal of phosphorus (P) from aqueous solution, due to its high composition of residual iron oxides such as hematite. Several studies have investigated the performance of bauxite residue in removing P; however, the majority have involved the use of laboratory "batch" tests, which may not accurately estimate its actual performance in filter systems. This study investigated the use of rapid, small-scale column tests to predict the dissolved reactive phosphorus (DRP) removal capacity of bauxite residue when treating two agricultural waters of low (forest run-off) and high (dairy soiled water) phosphorus content. Bauxite residue was successful in the removal of DRP from both waters, but was more efficient in treating the forest run-off. The estimated service time of the column media, based on the largest column studied, was 1.08 min g media for the forest run-off and 0.28 min g media for the dairy soiled water, before initial breakthrough time, which was taken to be when the column effluent reached approximately 5% of the influent concentration, occurred. Metal(loid) leaching from the bauxite residue, examined using ICP-OES, indicated that aluminium and iron were the dominant metals present in the treated effluent, both of which were above the EPA parametric values (0.2 mg L for both Al and Fe) for drinking water.