Advances In Groundwater Remediation: Achieving Effective In Situ Delivery Of Chemical Oxidants And Amendments

Contamination of soil and groundwater by organic chemicals represents a major environmental problem in urban areas throughout the United States and other industrialized nations. Over many decades a wide variety of toxic organic chemicals have intentionally or accidentally been released into the subsurface resulting in serious risks to human health and environmental quality (e.g., increased cancer risk through ingestion of contaminated drinking water or inhalation of vapors within buildings). In situ chemical oxidation (ISCO) has emerged as one of several viable methods for remediation of organically contaminated sites. Many of the most prevalent organic contaminants of concern (COCs) at sites in urban areas (e.g., chlorinated solvents, motor and heating fuels) can be destroyed using oxidants such as catalyzed hydrogen peroxide (H2O2), potassium permanganate (KMnO4), sodium persulfate (Na2S2O8), and ozone (O3). Based on laboratory experimentation, reaction stoichiometries, pathways, and kinetics have been established for many organic COCs. The reactions involve electron transfer or free radical processes with simple to complex pathways following 2nd-order kinetics with very fast reaction rates. The need for activation, sensitivity to matrix conditions (e.g., temperature, pH, salinity), and interactions with subsurface properties all vary between the different oxidants and site conditions. The ISCO systems that can be deployed in the field are highly varied in their features based on site conditions and cleanup goals. Cleanup goals generally specify one or more of the following objectives: 1) reduce the contaminant concentration or mass in a target treatment zone (TTZ) by some percentage (e.g., >90%), 2) achieve a specified post-ISCO contaminant concentration in a TTZ (e.g.,