TECHNOLOGIES / COMBINED TECHNOLOGY REMEDIATION
ADAPTABLE AND EFFECTIVE APPROACHES TAILORED TO SITE SPECIFIC CHALLENGES.
Rather than relying on a single method, combined remedy treatment leverages multiple technologies to create customized solutions that maximize efficiency and minimize environmental impact. While individual remediation technologies have distinct advantages, they also have limitations. A proactive combined technology approach enhances treatment performance, improves efficiency, and reduces cleanup time and costs by integrating multiple processes to overcome the limits of any single method.
Example Combined Remedies have included:
- ISCO followed by bioremediation
- Soil blending in the source area with downgradient injections
- Surfactant combined with ISCO
- Surfactant-Enhanced Recovery (SER) followed by ISCO
- Surfactant Enhanced Bioremediation (Enhanced Reductive Dechlorination)
- Injections in the saturated zone combined with soil vapor extraction in the unsaturated zone
- Sequential chemical oxidant injections (e.g., MFR followed by Activated Sodium Persulfate)
- Excavation followed by ISCO
- Excavation followed by bioremediation using a PRB
- ISCO injections in the source area with an activated carbon barrier
- In-situ soil mixing combined with ISCO
- Source excavation, ISCO beneath a road, and aerobic bioremediation downgradient
Case Study: Multiple Remediation Technologies for Brownfield Cleanup
A former manufacturing site in New York City participated in a voluntary remediation program to support redevelopment. Contamination at the site included TCE, petroleum hydrocarbons and metals, with impacts extending up to depths of 60 feet. To initiate construction activities, >20,000 tons of soil was excavated. ISOTEC collaborated closely with the project consultant and developer to implement in-situ remediation activities during the active construction phase.
- In-situ chemical oxidation was applied near TCE hotspots using sodium permanganate, chosen to allow oxidant advection despite limited access for injection well installation.
- Enhanced in-situ dechlorination injections to establish a permeable reactive barrier along the property boundary, using emulsified vegetable oil and zero-valent iron.
The project achieved a Conditional Track 1 cleanup and was a Big Apple Brownfield Award Recipient.
Case Study: Bioremediation Enhanced with Surfactant
At a former metal tool manufacturing site, remediation was implemented to address mineral oil LNAPL and chlorinated VOCs, primarily TCE and its dechlorination products. The project aimed to accelerate anaerobic biodegradation and reduce residual LNAPL. In areas where LNAPL and CVOCs coexisted, a customized surfactant was combined with sodium lactate injections to break up the LNAPL, dissolve CVOCs, and leverage the mineral oil LNAPL as an additional electron donor. Where LNAPL wasn’t present, emulsified vegetable oil was injected as a long-term carbon source. These injections took place at an active commercial plaza.
Case Study: Surfactant-Enhanced In-Situ Chemical Oxidation with Sodium Permanganate
At an urban brownfield site in New England, in-situ chemical oxidation (ISCO) was selected to treat PCE, with evidence of PCE DNAPL present at the site. Sodium permanganate was chosen for its long-lasting effectiveness and ability to treat VOCs beneath a building.
To optimize treatment, surfactant was added to enhance the desorption of PCE, making it more accessible for oxidation. Bench testing helped determine the ideal surfactant and dosing. Injections were sequenced from downgradient toward the source area to create an oxidation zone that would address VOCs mobilized by the surfactant.
- Surfactant-enhanced ISCO was applied to both unsaturated and saturated soils in areas with high PCE contamination.
- Three rounds of injections were conducted, with the scope of follow-up adjusted based on monitoring results. In the most impacted well, PCE concentrations dropped by more than 99%, from 27,000 µg/L to 32 µg/L.