TranslateChlorinated Solvent Remediation Services
Comprehensive strategies for treating PCE, TCE, DCE, vinyl chloride, and other chlorinated compounds using proven oxidation, reduction, and combined technologies
Treatment Technologies
Target Compounds
Mechanisms
- Persulfate radical (SO₄•⁻) oxidation: 2.60V potential
- Ferrate (Fe(VI)) oxidation: 2.20V potential
- Direct persulfate (S₂O₈²⁻) oxidation: 2.01V potential
- Secondary bioremediation via sulfate/iron electron acceptors
Advantages
- Rapid oxidation with sustained biological treatment
- Effective in all soil types including low permeability
- No rebound - combined oxidative and reductive mechanisms
- Single component system with integrated activator
- No exothermic heat generation
- Treats both dissolved and DNAPL phase
Limitations
- Higher cost than bioremediation alone
- Initial turbidity possible
- Requires site characterization for dosing optimization
Target Compounds
Mechanisms
- Sequential reductive dechlorination: PCE → TCE → DCE → VC → Ethene
- Dehalococcoides bacteria catalyze complete dechlorination
- Electron donors (emulsified oil, HRC) fuel anaerobic processes
- Hydrogenolysis and dihaloelimination pathways
Advantages
- Complete detoxification to ethene
- Cost-effective for large plumes
- Long-lasting treatment zones
- Proven for high concentration DNAPL
- Minimal site disruption
Limitations
- Requires anaerobic conditions
- Slow degradation of vinyl chloride without Dehalococcoides
- May stall at DCE without bioaugmentation
- Methane generation possible
- Sulfate/nitrate can inhibit process
Target Compounds
Mechanisms
- Direct reduction via ZVI: Fe⁰ + RCl → Fe²⁺ + R⁻ + Cl⁻
- Beta-elimination reactions
- Catalyzed H₂ generation supports bioremediation
- Food-grade surfactant enables ZVI distribution in low-K zones
Advantages
- Effective in low permeability formations
- Treats sorbed and DNAPL phase contaminants
- Long-term reductive capacity (years)
- IET proprietary emulsification technology
- Synergistic chemical/biological treatment
Limitations
- Requires subsurface mixing/injection
- Carbonates can passivate iron surface
- Not suitable for high sulfate environments
- Higher installation cost
Target Compounds
Mechanisms
- ZVI catalyzes H₂O₂ → hydroxyl radicals (OH•): 2.80V
- Ferrous iron activates persulfate → sulfate radicals (SO₄•⁻): 2.60V
- Residual ZVI provides long-term reductive capacity
- Sequential oxidation then reduction prevents rebound
Advantages
- Treats chlorinated solvents + 1,4-dioxane simultaneously
- Most powerful oxidation: hydroxyl + sulfate radicals
- Long-term treatment from residual ZVI
- Prevents contaminant rebound
- Effective on recalcitrant compounds
Limitations
- Complex chemistry requires expertise
- Higher material costs
- Careful ratio optimization needed
- May produce temporary turbidity
Degradation Pathways
PCE → TCE → cis-1,2-DCE → Vinyl Chloride → Ethene
Sequential removal of chlorine atoms under anaerobic conditions
Key Organism:
Dehalococcoides spp.
Conditions:
Anaerobic, electron donor required, pH 6-8
Chlorinated Solvent + SO₄•⁻ → CO₂ + Cl⁻ + SO₄²⁻
Direct mineralization via sulfate radicals
Key Mechanism:
Persulfate radical oxidation
Conditions:
Activator (Fe²⁺, Fe³⁺) required, all soil types
PCE/TCE + Fe⁰ → Acetylene/Ethene + Fe²⁺ + Cl⁻
Surface-catalyzed reduction and dechlorination
Key Mechanism:
Electron transfer at iron surface
Conditions:
No oxygen, low to moderate pH, low sulfate
Design Considerations
- Contaminant distribution (dissolved vs. DNAPL)
- Geochemistry (pH, redox, sulfate, nitrate, TOC)
- Geology and hydraulic conductivity
- Electron acceptor/donor availability
- Presence of co-contaminants (petroleum, metals, dioxane)
- PCE/TCE dominant → Persulfate or ERD
- High vinyl chloride → ERD with Dehalococcoides
- Low permeability → Persulfate or EZVI
- DNAPL source zones → High-dose persulfate or ERD
- Mixed contaminants → Combined oxidation systems
- Pilot test to optimize dosing and delivery
- Injection spacing based on geology (15-30 ft typical)
- Direct push or permanent wells depending on monitoring needs
- Performance monitoring: parent compounds, daughter products, geochemistry
- Contingency planning for stall or rebound
Specialized Chlorinated Solvent Treatment Methods
Enhanced In-Situ Dechlorination (EID)
IET delivers electron donor substrates (emulsified vegetable oil, HRC, lactate) combined with Dehalococcoides bioaugmentation cultures to drive complete sequential reductive dechlorination: PCE → TCE → DCE → vinyl chloride → ethene. IET's patented slow-release encapsulated substrates (US-9126244-B2) sustain reducing conditions for 2–5 years from a single injection event.
Permeable Reactive Barriers (PRBs)
IET designs and installs PRBs for passive long-term interception of chlorinated solvent plumes. Zero-valent iron (ZVI) or reactive media are installed in-situ to intercept groundwater flow, providing continuous abiotic dechlorination of TCE, PCE, and DCE as the plume migrates through. IET has installed PRBs at industrial, military, and dry cleaner sites nationwide.
Combined & Sequential Approaches
The most effective chlorinated solvent remediation often layers multiple technologies. A typical IET sequence: (1) ferric iron-activated persulfate ISCO destroys the DNAPL source zone; (2) the iron-amended subsurface transitions into a bioremediation-supporting reducing environment; (3) ERD/bioaugmentation addresses the dissolved plume to closure. One mobilization, multi-year treatment.
