Injection of reducing agents (zero-valent iron, calcium polysulfide, dithionite, ferrous iron) into the subsurface to abiotically degrade chlorinated solvents, energetics, and reducible metals such as hexavalent chromium.
In-Situ Chemical Reduction is the redox-opposite complement to ISCO. Reductants donate electrons to the contaminant, cleaving carbon-chlorine bonds in chlorinated solvents and reducing hexavalent chromium to the less mobile trivalent form. The dominant reductants are micro- and nano-scale zero-valent iron (ZVI), calcium polysulfide, sodium dithionite, and ferrous iron.
ISCR is most often deployed against chlorinated ethenes and ethanes (TCE, PCE, 1,1,1-TCA), energetics (RDX, TNT), and Cr(VI). Reaction byproducts are typically benign (ethene, ethane, chloride) but pH and ORP shifts can mobilize secondary contaminants, and short reagent lifetime can require multiple injection events. ISCR is increasingly combined with bioaugmentation, where the abiotic reduction primes the geochemistry for biological dechlorination.
Also known as: ISCR, in-situ chemical reduction.
In-Situ Chemical Oxidation (ISCO): treatment approach
In-situ chemical oxidation: injection of a chemical oxidant — permanganate, persulfate, or Fenton's reagent — directly into contaminated soil or groundwater to destroy dissolved-phase organic contaminants without excavation.
An ex-situ soil treatment process that heats contaminated soil to volatilize and separate organic contaminants from the soil matrix, after which the liberated vapors are captured and treated, usually in a high-temperature oxidizer.
A thermal desorption configuration where the heat source contacts the soil directly inside the rotary unit, delivering high heat-transfer efficiency and supporting higher treatment temperatures.
A thermal desorption configuration where heat is conducted through the wall of the treatment vessel without combustion gases contacting the soil, producing a concentrated, lower-volume vapor stream suitable for condensation and recovery.
Treatment that heats contaminated soil and groundwater in place, typically with electrical resistance, thermal conduction, or steam injection, to volatilize and recover contaminants without excavation. Used where excavation is impractical or where the contaminant zone sits beneath active infrastructure.