Countering Contaminant Rebound with Ferric Iron Activated Persulfate

A primary objective at Provectus is to identify limitations with established in situ remediation technologies and determine the best means to overcome these weaknesses. Chemical oxidation is an established in situ remedial option for a wide range of contaminants with thousands of contaminated sites reaching closure utilizing the technology. However, a continued limitation with chemical oxidation is sustained destruction of the contaminants within the targeted treatment zone due to the short-lived lifespan (e.g., hours to weeks) of the oxidants applied. The limited oxidant lifespan often leads to contaminant rebound and likely additional amendment field applications.

With its highest generated ORP and lowest activated energy requirement, an often overlooked benefit with ferric iron activated sodium persulfate (Provect-OX) is the long-term anaerobic bioremediation processes that are initiated after the persulfate is depleted. These bioremediation processes are effective destruction pathways to counter contaminant rebound and achieve low groundwater standards (e.g., <5 µg/L).

Site Overview — Manalapan, New Jersey

An active auto service center in Manalapan, New Jersey that Engineering & Land Planning Associates, Inc. (E&LP) was managing required in situ remediation to address a comingled petroleum hydrocarbon and chlorinated solvent plume. E&LP was familiar with the aggressive chemical oxidation nature of the Provect-OX technology for addressing high-level contaminant mass, and the firm was also attracted to the long-term anaerobic bioremediation processes that would treat sorbed mass release and prevent contaminant rebound.

Primary contaminants at the site included benzene, ethylbenzene, xylenes, 1,2,4-trimethylbenzene, tetrachloroethene, and trichloroethene. The remedial program was developed by E&LP and Provectus Environmental with >13,000 lbs of Provect-OX applied via 28 direct push points in July 2020.

Two-Year Results

"ORPs were measured as high as +502mV following treatment and transitioned to intended bioremediation reducing conditions with ORP values of -167mV maintained two years post-treatment."

After approximately two years of monitoring, the data outlines the chemical oxidation and anaerobic bioremediation conditions anticipated after a ferric iron activated persulfate application. Specifically, ORPs were measured as high as +502mV following treatment and transitioned to intended bioremediation reducing conditions with ORP values of -167mV maintained two years post-treatment.

Furthermore, the sulfate levels have decreased by 61% and 86% at the target monitoring wells in that same period, providing further evidence that biological attenuation was occurring. Most importantly, the contaminants exceeding groundwater quality standards were significantly reduced following the Provect-OX application with an established 2-year declining trend.