Topic Area: 5d. Combined Treatment of Emerging Contaminants with CVOCs

Formatted Title:

Application of Combined SVE and Cryogenic Cooling Compression (C3) Technology as Cost-Effective Remedial Action at a Highly Solvent-Contaminated Site in California

Background/Objectives:

Parsons designed, installed, and is currently operating and monitoring a combined soil vapor extraction (SVE) and cryogenic cooling compression (C3) remediation system at a highly solvent-contaminated former paint manufacturing site in California. Solvents were stored on site in underground storage tanks (USTs) or aboveground storage tanks (ASTs) from the 1920s until 2006. Previous soil, soil vapor, and groundwater investigations were conducted between 1986 and 2015. Site contaminants of concern (COCs) include, but are not limited to, benzene, toluene, ethylbenzene, and xylenes (BTEX), methylene chloride, trichloroethene (TCE), and tetrachloroethene (PCE). An SVE pilot study was conducted in 2017 to assess the radius of influence (ROI) and the viability of the SVE system to remove volatile organic compounds (VOCs) in soil to protect against vapor intrusion risks associated with on-site buildings. Based on results of the pilot study, the full-scale combined SVE and C3 system was installed to address on-site impacted soil and soil vapor from the vadose zone. Traditional SVE systems with granular activated carbon (GAC) treatment would be costly and would not work for this site because high concentrations of VOC influent exhaust GAC quickly, methylene chloride, one of the primary COCs, does not adsorb onto GAC easily, and the high methylene chloride/toluene concentrations in vapor are very corrosive to some of the traditional construction materials for just an SVE GAC system. The combined SVE and C3 system was proposed as a more efficient and cost-effective remediation system for the Site. As vapor concentrations decrease over time, the C3 unit will be removed and the SVE system will be modified to operate with a GAC filtration unit potentially supplemented with zeolite. The objective of this study is to better understand the selection, application, effectiveness, and cost evaluation of the combined SVE and C3 technology at highly solvent-contaminated sites where traditional SVE system remediation might be costly or ineffective.

Approach/Activities:

The primary components of the SVE system include a C3 technology-equipped vapor extraction, treatment, and non-aqueous phase liquid (NAPL) reclamation system with a vapor/liquid separator, compressor, blower, and after-cooler. The C3 system contains a refrigeration/condensation unit with regenerative adsorber beds. The system is also equipped with GAC treatment (for polishing after the C3) prior to vapor stream discharge to the atmosphere. Single and dual-nested SVE wells were installed with screen intervals at different depths as upper and lower zone extraction wells based on the areas of contamination and lithology. Continuous operation and system optimization on the SVE well field began on June 16, 2022, until present. The effectiveness of the SVE system is being monitored through performance metrics that include mass recovery trends from SVE influent vapor sampling, flow readings, and liquid condensation collection on a monthly basis. Selected SVE wells are also sampled monthly to evaluate and compare against expected reduction in soil vapor concentrations over time in individual wells and areas of the Site. Progress towards meeting remedial objectives continue to be evaluated from data obtained during ongoing O&M activities. The cost of system operation and maintenance, carbon vessels changeout, and liquid phase waste management were also collected for cost evaluation and comparison.

Hao Zhang

Affiliation

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(Group 1, Poster Board #61) Application of Combined SVE and Cryogenic Cooling Compression (C3) Technology as Cost-Effective Remedial Action at a Highly Solvent-Contaminated Site in California