Installation of a permeable reactive barrier in the containment of acid pollution

A permeable reactive barrier (PRB) filled with recycled concrete aggregates was installed in the Shoalhaven Floodplain, about 70 km South of Wollongong City in Australia. The purpose of this PRB was to treat the acidic groundwater generated from acid sulfate soils, which contribute to serious damage to the environment, and productivity. The intention of the current study was to model the performance of the PRB, whereby geochemical reactions were coupled with geo-hydraulics. Precipitated secondary minerals during the treatment process usually accumulate on the pore spaces (clogging) and on the reactive surfaces (armouring) of recycled concrete aggregates. Clogging and armouring reduce the porosity and hydraulic conductivity of the reactive media. Finite different codes available in MODFLOW and RT3D software were utilized for time-dependent modelling. The model predictions were in agreement with the laboratory and field data. Porosity and hydraulic conductivity reductions were maximum at the entrance of the PRB and almost insignificant at the middle and exit zones of the PRB.