Former Hardware Store Site — Adamsville

A unique mix of chemical oxidation and facultative biologically based mineralization was used to degrade benzene, toluene, ethylbenzene and xylene compounds present in soil and groundwater at a hardware store site in Adamsville, Ohio.

The utilization of free radical chemistry was implemented in such a way as to extend the oxidant and free radical residuals. The injection program effectively introduced the remedial chemicals sodium persulfate, hydrogen peroxide and zero-valent iron directly into the soil and groundwater using injection wells and direct push technologies.

The injection program targeted a total of 2,502 square feet.

The first phase of the degradation program oxidizes VOCs via hydroxyl and sulfate free radicals, utilizing zero-valent iron as a catalyst for both reactions. This step is then followed by the enhancement of biological attenuation using the spent materials from the oxidation event to aid in facultative biological degradation of the dissolved phase compounds remaining after the oxidation event.

This Adamsville project demonstrates IET's patented (US 7,044,152) dual-oxidant activation technology — using 1,241 lbs of ZVI to simultaneously activate 5,180 lbs of sodium persulfate in a single injection event. The ZVI catalyst generates sulfate radicals (SO₄•⁻) from persulfate and hydroxyl radicals (•OH) from peroxide, creating a multi-radical oxidative environment that destroys BTEX and aromatic hydrocarbons more effectively than either oxidant alone.

The dual-phase treatment design — oxidation followed by biological attenuation — leverages the spent oxidant by-products as electron acceptors for facultative biological treatment. After the ZVI-activated oxidants are depleted, the residual ferric iron and sulfate species support biological degradation of remaining dissolved-phase contamination. This mechanism provides both rapid source destruction (97% benzene reduction in MW-1) and sustained long-term treatment, preventing the contaminant rebound that plagues single-oxidant ISCO programs.

The 570-day post-injection monitoring period documented in the treatment results demonstrates the sustained effectiveness of this dual-phase approach. The 97% benzene reduction in MW-1 and 95% benzene reduction in MW-5, maintained over 570 days, confirm that the biological attenuation phase successfully followed the oxidation phase — providing the long-term treatment needed for complete petroleum site closure.

The BTEX and aromatic hydrocarbon contamination at this site is typical of former petroleum storage or distribution facilities. The 700 gallons of ZVI suspension and 2,825 gallons of oxidative solution delivered via direct push injection provided comprehensive coverage of the contaminated soil and groundwater zone, with the ZVI-activated dual-oxidant chemistry targeting both dissolved-phase and sorbed-phase contaminants.

The cost-effective single-event treatment noted in the Key Success Factors is a significant advantage of IET's dual-oxidant approach. By activating both persulfate and peroxide with ZVI in a single injection event, the project avoids the cost of multiple mobilizations while achieving the treatment effectiveness of a multi-phase program. The sustained reducing conditions established by the residual ZVI and biological community provide ongoing treatment without additional field events.