In Situ Remediation Techniques: A Comprehensive Guide
ISCO, ISCR, ERD, bioremediation, EZVI, ISGS, and NAPL treatment — explained by the specialists who developed and patented many of these technologies. 28 years, 3,000+ projects, 14 US patents.
In-Situ Chemical Oxidation (ISCO)
Destroy organic contaminants underground using powerful chemical oxidants.
How It Works
ISCO introduces chemical oxidants directly into contaminated soil and groundwater to chemically destroy organic contaminants on contact. Three primary oxidants are used in environmental remediation: • Activated Persulfate — IET's patented ferric iron-activated persulfate generates sulfate radicals that aggressively oxidize chlorinated solvents and petroleum hydrocarbons, providing sustained treatment for 12–24+ months from a single injection event. • Potassium Permanganate — A strong oxidant effective against chlorinated ethenes (TCE, PCE). Produces stable MnO₂ precipitate used by IET's ISGS technology for NAPL flux reduction. • Catalyzed Hydrogen Peroxide (Fenton's Reagent) — Fast-acting and aggressive, ideal for petroleum hydrocarbons and BTEX. Requires careful pH management and is best for source zone treatment.
Detailed ISCO PageContaminants Treated
- TCE / PCE / DCE / Vinyl Chloride
- BTEX / Petroleum Hydrocarbons
- DNAPL / NAPL Source Zones
- PAHs / Creosote
- MTBE
- Mixed Organics
Key Advantages
- Rapid mass reduction (weeks to months)
- Destroys contaminants — no waste transfer
- Patented 2+ year sustained oxidation
- Compatible with follow-on bioremediation
Enhanced Reductive Dechlorination (ERD) & Bioremediation
Harness microbial populations to biodegrade contaminants over time.
How It Works
Enhanced Reductive Dechlorination (ERD) stimulates anaerobic microorganisms to sequentially strip chlorine atoms from chlorinated solvents (TCE → DCE → vinyl chloride → ethene). Electron donor substrates create the reducing environment required: • Emulsified Vegetable Oil (EVO) — Long-lasting (3–7 years) slow-release substrate. IET's Provect ERD formulations are specifically engineered for sustained ERD performance. • Bioaugmentation — When sites lack sufficient native dechlorinating organisms, IET injects specialized cultures (KB-1®, SDC-9®) containing Dehalococcoides (DHC) bacteria that drive complete dechlorination to ethene. • Aerobic Bioremediation — For petroleum hydrocarbons and BTEX, oxygen-releasing compounds or air sparging stimulate aerobic degradation by native bacteria.
Detailed ERD / Bioremediation PageContaminants Treated
- TCE / PCE / DCE / Vinyl Chloride (anaerobic)
- BTEX / Gasoline / Diesel (aerobic)
- Petroleum Hydrocarbons
- MTBE (aerobic/co-metabolic)
Key Advantages
- Most cost-effective for dilute dissolved plumes
- Long treatment duration from single injection
- Achieves complete mineralization to ethene
- Works synergistically with ISCO pre-treatment
In-Situ Chemical Reduction (ISCR)
Transform chlorinated solvents and heavy metals through reductive chemistry.
How It Works
ISCR uses reducing agents to chemically transform contaminants via electron transfer reactions — the opposite mechanism from oxidation. Key reducing amendments include: • Zero Valent Iron (ZVI) — Metallic iron donates electrons to chlorinated solvents, breaking C-Cl bonds through abiotic dechlorination. Also reduces hexavalent chromium Cr(VI) to immobile Cr(III). • Nano-Scale ZVI (nZVI) — Sub-micron iron particles with enormously increased reactive surface area, deliverable via direct push or recirculation to reach deep DNAPL source zones. • Sodium Dithionite — Creates a strongly reducing subsurface zone that persists for years, providing long-term conditions for contaminant destruction and metal immobilization. ISCR is the preferred approach when oxidizing agents are contraindicated — for example, at sites where ISCO could mobilize co-contaminant metals.
Detailed ISCR PageContaminants Treated
- TCE / PCE / DCE (abiotic dechlorination)
- Hexavalent Chromium Cr(VI)
- Uranium and Technetium
- Mixed chlorinated + metals plumes
Key Advantages
- No oxidant mobility concerns for metals sites
- Long-term sustained reducing conditions (5–10 yrs)
- Abiotic + biotic combined degradation with ZVI
- Effective for Cr(VI) and mixed contamination
Emulsified Zero Valent Iron (EZVI)
Deliver iron directly into DNAPL source zones via oil-encapsulated nanoparticles.
How It Works
EZVI is a NASA-licensed technology consisting of nano-scale zero valent iron particles encapsulated in a biodegradable oil-in-water emulsion. This formulation exploits a critical chemical principle: like dissolves like. When injected near chlorinated DNAPL (e.g., TCE or PCE pools), the oil phase of EZVI preferentially partitions into the NAPL, carrying the reactive iron directly to the contaminant source. Degradation occurs through two simultaneous mechanisms: 1. Abiotic Chemical Reduction — ZVI directly dehalogenates chlorinated DNAPL molecules. 2. Biotic Reductive Dechlorination — The oil phase serves as a long-term electron donor for indigenous or augmented Dehalococcoides bacteria. This dual mechanism makes EZVI uniquely effective for deep DNAPL source zones that are largely inaccessible to purely aqueous-phase amendments.
Detailed EZVI PageContaminants Treated
- Chlorinated DNAPL (TCE, PCE free phase)
- Residual NAPL in soil pores
- High-concentration chlorinated solvent source zones
Key Advantages
- Directly contacts and partitions into DNAPL
- Dual abiotic + biotic degradation pathways
- Provides long-term electron donor for ERD
- NASA-licensed; deployed nationally by IET
In-Situ Geochemical Stabilization (ISGS)
Mechanically mix treatment reagents into contaminated soil to overcome injection limitations.
How It Works
ISGS (licensed exclusively by IET from Evonik) applies modified permanganate reagent solutions through mechanical soil mixing or horizontal directional drilling (HDD) injection into NAPL-impacted source zones. The oxidant migrates through the treatment area, destroying dissolved-phase organics and chemically weathering NAPL residuals — progressively reducing viscosity, solubility, and flux into groundwater. The MnO₂ precipitate formed during oxidation accumulates along the NAPL front, further restricting contaminant migration. IET performed the first-of-its-kind unidirectional HDD injection of ISGS reagent at a NJ Superfund site — delivering over 100,000 gallons of treatment beneath an active highway, demonstrating that ISGS can reach zones inaccessible to vertical drilling.
Detailed ISGS PageContaminants Treated
- NAPL / DNAPL Source Zones
- MGP / Coal Tar / Creosote
- PAHs in low-permeability soils
- Mixed NAPL + dissolved-phase sites
Key Advantages
- Treats zones inaccessible to standard injection
- Licensed exclusively in North America by IET
- HDD delivery under structures/highways
- Mass removal + long-term flux reduction
NAPL & Source Zone Treatment
Eliminate the persistent source driving dissolved-phase groundwater plumes.
How It Works
NAPL (non-aqueous phase liquid) source zones are the dominant driver of persistent, long-lived groundwater contamination. Without source treatment, dissolved plumes persist for decades even with pump-and-treat management. IET's NAPL treatment strategy depends on NAPL type: • Chlorinated DNAPL (TCE/PCE pools) — EZVI for direct source contact, high-concentration ISCO persulfate or permanganate for residual DNAPL oxidation, and ISGS for mechanically distributed treatment. • Petroleum LNAPL (gasoline, diesel free product) — ISCO (hydrogen peroxide), aerobic bioremediation, or SVE/AS depending on depth and soil type. • Coal Tar / Creosote (MGP sites) — ISGS soil mixing with permanganate-based reagents is IET's primary approach for high-viscosity, high-mass NAPL at manufactured gas plant sites.
Detailed NAPL Treatment PageContaminants Treated
- Chlorinated DNAPL (TCE, PCE, 1,1,1-TCA)
- Petroleum LNAPL (gasoline, diesel, fuel oil)
- Coal tar and creosote (MGP sites)
- Mixed NAPL with dissolved-phase plumes
Key Advantages
- Addresses root cause of persistent plumes
- Reduces dissolved-phase loading long-term
- Enables faster regulatory closure
- Avoids excavation and landfill disposal costs
Technique Comparison at a Glance
| Technique | Mechanism | Speed | Best Zone |
|---|---|---|---|
| ISCO | Chemical oxidation | Weeks–months | Source + plume |
| ERD / Bioremediation | Microbial degradation | 2–5 years | Dissolved plume |
| ISCR | Chemical reduction | Months–years | Source + metals |
| EZVI | Chem. reduction + bio | 1–3 years | DNAPL source zone |
| ISGS | Oxidation + stabilization | Months | NAPL source zone |
| NAPL Treatment | Technology-specific | Variable | Source zone |
Common Questions
Which Technique Is Right for Your Site?
IET's engineers have designed and implemented all six techniques across 3,000+ sites. Get a site-specific recommendation today.