In Situ Treatment of Arsenic-Contaminated Groundwater via Extraction Well–Integrated Permeable Reactive Barriers

Abstract

A pumice–maghemite (P-maghemite) composite was developed using the chemical coprecipitation method with a 20% iron loading ratio by weight. The characterization of the composite using SEM and XRD indicated the effective loading and dispersion of nanoparticles on the surface of the developed base materials. Thereafter, in situ sequestration experiments were conducted in the laboratory for an arsenic-polluted aquifer system using two well-integrated permeable reactive barrier (PRB) modules filled with the developed composite. A vertical fixed-bed column setup was used for the columnar PRB, whereas a sand tank experimental setup was employed for the well-screen-integrated PRB; both PRB systems were fed by a synthetic solution representing the arsenic-contaminated groundwater. More than 99% arsenic removal was observed in the columnar PRB, with an average effluent concentration of 4 μg/L at the end of the experiment, which is well below the acceptable limit of drinking water for arsenic (<10 μg/L). Removal of arsenic by the 4-cm-wide well-screen-integrated PRB from 652 μg/L to less than 20 μg/L shows a great potential of the developed composite for arsenic remediation at slower groundwater flow rates. A maximum arsenic removal of 99% was attained at the start of the experiment, which decreased to 97% after 1 month of PRB operation. The effluent concentration of all other major ions also was reduced considerably in the PRB modules. The hydraulic conductivity of the developed media was reduced by 35% in the columnar PRB and by approximately 20% in the well-screen-integrated PRB. The high arsenic removal efficiency in continuous flow-through remediation systems indicates the applicability of the developed PRB system in in situ remediation of arsenic-contaminated groundwater.