Bauxsol™ based barriers for the treatment of metal contaminated ground waters

Bauxsol™ and its derivatives are manufactured products of bauxite refining residues, however Bauxsol™’s grained nature tends to limit the use of it in permeable reactive barriers because the hydraulic conductivity is very low (<10⁻⁹ m/sec). However, if Bauxsol™ is blended with sand in a ratio of about 70:30 sand:Bauxsol™ permeability increases to about 1x10⁻³ to 1x10⁻⁴ m/sec and reasonable water flows occur. Presented are the results of a small ≈1m³ (2m² of permeable surface area) barrier consisting of 70:30 sand:Bauxsol™ that has hydraulic conductivity of 9.8x10⁻⁵ m/s that was constructed across an ARD flow. The barrier effectively treated 45,000L of ARD (acid rock drainage) water to ANZECC (2000) drinking water standards, and 27,000L to Protection of Aquatic Ecosystems limits. Additional laboratory-scale tests using activated Bauxsol™/sand mixtures, to treat an artificial groundwater with an As(v) concentration of 300 μg/L (4 μM/L) are presented. These studies suggest there is potential to use of Bauxsol™ in permeable reactive barriers, but the proportion of active material needs to be increased to improve performance; pelletisation would be an effective way to increase permeability and increase Bauxsol™ content.