In situ chemical reduction (ISCR) can help you meet your contaminant destruction goals and, in many cases, with fewer events in a way that bioremediation and in situ chemical oxidation (ISCO) can’t achieve.
ISCR uses both biological and abiotic reducing agents like zero valent iron (ZVI) and other combined formulations to change contaminants into less toxic or less mobile forms. It’s conducted in place without excavating soil or pumping groundwater above the surface. While able to clean up several contaminants, ISCR is most often used to remediate chlorinated solvents.
Hydrolysis and the beta elimination pathway are the primary chemical reactions when using ZVI to reduce chlorinated solvents. A small percentage of the reaction will also follow the biotic dechlorination pathway for degradation to ethene.
ISCR can be used for source reduction, such as DNAPL remediation zones, and in reactive treatment zones in the plume or site boundary.
It’s generally applied in fine-grained soils where liquids cannot be effectively distributed under high pressure and, more recently, in transmissive zones with < 5 um ISCR amendments. ISCR can be combined with bio substrates and bioaugmentation (ISCR-enhanced bioremediation) for a more aggressive abiotic/biotic treatment that can minimize the production of PCE and TCE daughter products, CIS 1,2 DCE or VC.
Two ways Cascade brings reducing agents into contact with contaminated soil and groundwater are direct low-pressure injection and higher-pressure hydraulic or pneumatic fracturing.
Direct injection of Colloidal iZVITM (< 5um) dilutes the injectable ZVI with water and pumps it through injection wells or DPT injection tools.
Fracturing with SourceKillTM or micro-scale ZVI (> 5um) involves exceeding the fracture pressure of adjacent soils to create or enhance new flow paths. These fractures can be created with nitrogen, water or the ISCR amendment itself. Once fracturing is complete, which usually takes a few seconds, injection of the solid slurry proceeds with pumps, like progressive cavity, piston or positive displacement pumps.
ISCR is a highly persistent chemistry, which means it will be around and ready to treat contaminants as they desorb from the soil, which has been the issue with less persistent chemistries at sites with contaminant mass sorbed to soil.
Performing ISCR reagent injection correctly involves the following steps:
ISCR is an advanced technique for reducing contaminants that can provide long-lasting results at your site. When you understand what ISCR is, how it works and the frequent reasons for using it, you’ll be better prepared for effective remediation.
Learn more about how ISCR works in a real-world application in this DNAPL remediation project highlight.
I also invite you to join me for next week's webinar, More Money, More Delays: How to Limit Cost Overruns and Remediation Problems With New Technology and Approaches. I'll be talking about how we can more effectively address problems like emerging contaminants, solvent and petroleum rebound, and unintended chemistry mobility.