Theme: 08. Metals

Topic Area: 8c. Precipitation and Stabilization of Metals

Formatted Title:

Bench-Scale Test for Precipitation and Stabilization of Metals

Background/Objectives:

Environmental studies in an industrial site in Brazil identified groundwater impact with dissolved metals, primarily manganese and secondarily boron and zinc. Within that context, a bench-scale test for chemical reduction of dissolved metals was conducted to verify the reduce of the concentrations by immobilization and precipitation. Also, data operation was collected to support the subsequent execution of a pilot test in situ.

Approach/Activities:

The bench-scale test was performed using a reductor product. Saturated soil and groundwater contaminated with COCs were collected at the two distinct hot spots in the industrial site. Upon collection, samples were prepared in the laboratory with mixing the soil and groundwater in 24 reactors. Two different concentrations of the reductor product were dosed in 16 reactors and for a control evaluation, in eight reactors no remediation products were added. In each reactor a baseline sample of groundwater was collected; after the dosage of reductor product was collected in groundwater samples at four-time intervals to evaluate degradability of COCs. The bench-scale test had a duration of 60 days.

Results/Lessons Learned:

Based on the analytical results of the COCs, the reductor product was efficient in reducing the concentration of dissolved metals manganese, boron, and zinc. The detection of increased sulfate concentration in the reactors with addition of the reductor product indicated the role of the reactions for the generation of metals complex thus precipitation and immobilization of dissolved metals. Results indicated 90% performance in reduction of COCs at the end of the test. Based on these results execution of a pilot test in situ was proposed, which is aimed at assessing the spatial distribution of reductor product the aquifer and at checking the efficiency of the injections in COC reduction.

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Allan Fuse