Theme: 01. Remediation Technology Innovations

Topic Area: 01d. Combined Remedies and Treatment Train Technologies

Formatted Title:

Combined ERH and ISCR Site

Background/Objectives:

The contaminated area is in the southern region of Brazil and has a history of industrial use dating back to the 1930s. The goal is to rehabilitate this land for residential purposes. Environmental investigations have revealed the presence of significant contaminants, specifically chlorinated ethenes including tetrachloroethene (PCE), trichloroethene (TCE), and vinyl chloride (VC) in the groundwater. Concentrations of these contaminants exceed acceptable limits for inhalation exposure scenarios, with some "hotspots" showing concentrations of approximately 580 mg/L of TCE, 190 mg/L of PCE, and 15 mg/L of VC.

To address these issues, an Intervention Plan was developed, which includes a combination of remediation measures, engineering solutions, technical controls, and the involvement of relevant institutions. The aim is to mitigate potential risks for future residential use of the land.

Two distinct remediation techniques were chosen: reductive dechlorination will be applied within the project's internal plume areas, specifically where concentrations of contaminants exceed the acceptable limits for vapor inhalation in indoor residential environments. In parallel, electrical resistance heating (ERH) will be used in areas with the highest concentrations. This method will operate from the shallow aquifer to the fractured aquifer. The choice of these techniques takes into account their technical feasibility and the financial viability for the project. While each technique alone might be insufficient, their combined use allows for effective land rehabilitation.

Groundwater remediation through reductive dechlorination was carried out between 2020 and 2021, spanning approximately four months. This involved the application of the remedial product MO-40 in pits and trenches. Monitoring was conducted throughout the environmental remediation process to assess its effectiveness.

The thermal remediation technique began operation in 2020 and is currently in progress. The areas for ERH treatment have been divided into several phases due to electrical capacity limitations.

Approach/Activities:

Two remediation techniques were used: reductive dechlorination and thermal remediation for the purpose of reclaiming land contaminated by CVOC solvents.

In areas with CVOC concentrations exceeding the inhalation criteria for closed residential environments (particularly within the first few meters of the aquifer), the reductive dechlorination technique was chosen. This involved applying the reducing product MO-40 (officially registered by the company Metalorganis under the reference number 11762/18-04 as a physical-chemical remediator with IBAMA) through excavated trenches.

Results/Lessons Learned:

The results obtained thus far have shown that directly applying the reducing product to the aquifer through mechanical mixing in excavated trenches using a backhoe has effectively reduced contamination in the trench areas, the surrounding vicinity, and even at greater depths beyond the mixing zones. This approach has also proven successful in safeguarding the land's boundaries with neighboring properties. Remediation monitoring, which included assessing physical-chemical parameters and volatile organic compound (VOC) analysis in groundwater, confirmed excellent outcomes in the areas where reductive dechlorination was implemented. In these regions, all analyzed parameters were quantified below the established criteria for vapor inhalation in the project's scenario, underscoring the effectiveness of the remediation method.

The remediation of the source areas is being performed using ERH technology, administered by the company TRS DOXOR. The initial phases of ERH treatment are currently in progress and have shown their effectiveness by meeting the objectives related to indoor inhalation safety.

The key to combining the reductive dechlorination and thermal reduction methods lies in a well-defined technical strategy. This strategy encompasses the selection of areas for each remediation technique, the timing of their application, and the outcomes they produce. Furthermore, it considers the unique advantages offered by each remediation method.

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Maurício Sabbag