XDD Environmental was contracted by CHA Companies to evaluate the impacts of varying temperature on the treatment of VOCs and SVOCs on soils via thermally enhanced soil vapor extraction (SVE) and / or thermally enhanced bioremediation. The original, more costly, design called for dewatering and high-temperature thermal conduction heating to raise soil temperatures and volatilize the site contaminants for SVE treatment.
Results and Achievements:
- Treatability testing indicated a 35 °C soil temperature (without nutrient amendment) increased biodegradation, which reduced contaminants to meet site goals (standard high-temperature thermal treatment remedies generally heat site soil to 100 °C).
- The treatability data showed bioremediation as the key VOC and SVOC destruction mechanism.
- Full-scale performance monitoring evaluations indicated that 86% of the VOC and SVOC mass reduction was from biodegradation (in agreement with the treatability test results). The remaining mass reduction was from thermally enhanced SVE.
- After 12 months, a 90% system shutdown was approved by the regulatory agency.
- After 18 months, the remedial goals were achieved and the system was decommissioned.
- The reduced temperature system operation resulted in an estimated 50% savings in electrical costs (2,700,000 kWh vs 5,300,000 kWh for full thermal).
- Additionally, the system required fewer wells and less general infrastructure, reducing the overall footprint of the remedy.