Modeling of mineral fouling in an alkaline permeable reactive barrier in Australia

Progress in the remediation of acidic groundwater generated from acid sulfate soil was achieved through the utilisation of an innovative geotechnical engineering technique, namely the installation of an alkaline Permeable Reactive Barrier (PRB) using recycled concrete particles as the reactive material in the Shoalhaven Floodplain, southeast New South Wales (NSW), Australia. The performance of the PRB has been monitored since its installation in October 2006 and it has proved effective in neutralising groundwater from similar to pH 3 to 7.3 and removing similar to 95% of Al and Fe from the groundwater. A key outcome of this study was to develop an original model capturing geochemical reaction kinetics coupled with transient groundwater flows, supported by detailed laboratory and field testing. The model could predict the porosity and hydraulic conductivity due to secondary mineral precipitation. The hydraulic conductivity reduction in the field is only 3% at the entrance face and almost negligible in the middle and exit zones to date.