Bench-Scale Flushing Experiments for Remediation of Hg-Contaminated Groundwater

Bench-scale laboratory column experiments were conducted to determine the desorption characteristics of Hg in the aquifer material from an area of known elevated Hg concentrations in groundwater under flushing conditions. The experimental results showed that columns packed with perched aquifer material (PA) showed flushing of Hg, with the general decline of effluent Hg concentrations over time (from 0.05-0.1 mg/L in the beginning to 0.0001-0.003 mg/L at the end of the experiment). Columns with lower aquifer material (LA) showed nondetectable level of effluent Hg throughout the experiment. Possibility of redissolution/desorption of Hg after static condition (for the duration of 18 days) was tested, showing only slight rebound of Hg concentrations after equilibration. The results suggest that removal of up to 20% of Hg inventory in the sediment could be achievable for the duration of the experiments (about 10 pore volumes). The results also indicate that the treated water from the water treatment plant was more effective compared to deionized water, probably due to complexing agents contained in the treated water.