Contaminated Land 1. Full-Scale Remediation Technologies Engineering Methods Solidification and Stabilisation Biological Physical Chemical Thermal

Engineering Methods Excavation and Landfill –Incomplete solution, –Landfill often pollutes (gas and leachate) –Relatively cheap, low risk On-site Disposal – Landfill area created on part of the site Planning Consent –Transport costs reduced Restructuring –Excavation and grading of contaminated soil –Mixing of heavily and lightly contaminated fractions –Restructured Fill Material –contaminant concentrations reduced below SGV

Engineering Methods Use of Covers Provides containment improves structural and engineering properties sustains vegetation only useful above a water table if Contaminant migration understood Covers Comprise top/sub-soil low water-permeability layer break layer –coarse granular, low capiliarity (avoids soil suction) specific layers –bio-, chemical, gas venting, drainage, filter Contaminated layer

COVERS

Engineering Methods In-Ground Barriers (Vertical / Horizontal) (grouting and membranes) Displacement Systems –Sheet Steel Piling –Vibrated Beam Wall Excavated Barriers –Secant Piling Wall –Shallow cut-off Walls or Slurry Trench Walls ( may include membrane) Injected Barriers –Chemical Grouting –Jet Grouting –Auger mixing Others –Electro-kinetic barriers, Ground Freezing

Engineering Methods Grouting Materials PFA / Cement Cements Cement / Clay Cement / Bentonite Bentonite / Cement Bentonite / Chemical Silicates Phenolic Resin lignins Acrylamides Aminoplasts Polyurethane

GROUTING, BARRIERS

Engineering Methods Hydraulic Measures Containment –temporary method (rapid implementation ) Free Product Recovery –depression of groundwater (cone) –induced gradient Reversal of Groundwater Vertical Flow –contaminated water diverted from entering sensitive strata Funnel and Gate / Reactive Barriers –(see later)

CONTAINMENT

Solidification & Stabilisation Overview and Principles Solidification and Stabilisation Technologies Ex Situ 1. Cement and Pozzolanic Based Systems 1b. Lime Based Systems 2. Vitrification In Situ 3. Cement and Pozzolanic Based Systems 4. Vitrification Examples

Solidification & Stabilisation Overview and Principles Stabilisation Chemical fixation of soluble components –metal sulphides and hydroxides Accessibility is reduced, gives reduced Toxicity Solidification Formation of a monolithic mass (good mechanical strength) Entrapment and occlusion Low-permeability (non-leachable) Vitrification Formation of Glass-like solids Metals immobilised

Solidification & Stabilisation Overview and Principles Long Term Stability breakdown due to action of: – acids, freeze-thaw, oxidation Physical Characteristics Better (reduced) Leachability and Mobility Volume increase Improved handling (vs. sludges) Improved mechanical properties (loads) Soil Structure and fertility –severe adverse effects

Solidification & Stabilisation Ex Situ Technologies 1. Cement and Pozzolan- Based Systems –Mixture selection (Laboratory) –Excavation –1. Mixing in Processing Plant (cf. concrete batch plant) –2. Direct Mixing (construction equipment) –Fill with stabilised material significant volume increase Chemical Basis –Portland Cement physical entrapment Insoluble metal hydroxides –Pozzolans (e.g. PFA) Silicates and Aluminates form Ca silicate gel with CaO Binders –Organophilic clay –asphalt (bitumen) emulsions

Solidification & Stabilisation Ex Situ Technologies 1b. Lime Based Systems For soils containing Pozzolan-like materials Based on hydration of Lime CaO + H 2 O  Ca(OH) 2 + heat Calcium hydroxide Encapsulates Contaminant Subsequent Reaction with Carbon dioxide in air –Solid carbonate coating Pretreatment of Hydrophobic contaminants –stearic acid reagent

Solidification & Stabilisation Ex Situ Technologies Time –Intensive (days - weeks) Costs (Ex situ) –S/Stabilisation £60 per m 3 Resources –high for Plant –high for manpower Application Range –Inorganics (metals, non-metals, cyanides) –asbestos –PCB, PAH –Oil

Solidification & Stabilisation Ex Situ Technologies 2. Vitrification Hot-Top Glass Furnace –1500C for 10 hours –lime, alumina and sand additions Air Emission Control –volatiles Soil Pretreatment –washing to reduce treated volume –max 10% soil organic matter Glass Frit –composition 40% CaO, 27% SiO 2, 14% Al 2 O 3, 10% Waste Plasma-Arc Furnace –2-Stage Plasma Furnace (melt) Combustion Furnace ( oxidation of organics)

Solidification & Stabilisation Ex Situ Technologies Time –Intensive (hours - days) Costs (Ex situ) –Vitrification > £500 per tonne Resources –very high power consumption –manpower - excavation, transport, process –Plant - excavation and furnace Application Range Primary –metals –asbestos Secondary –all organic contaminants oxidised, pyrolysed, or treated in gas emission

Solidification & Stabilisation In Situ Technologies 3. Cement and Pozzolan-Based Systems Batch mixing Plant –process additives prepared for injection Soil Mixing Equipment Soilcrete jet grouting Auger Mixing Equipment (Secant Piling) –Multiple Auger (15RPM) –Enclosed Shallow Mixing Auger (dry reagents) Overlap of columns to cover site

Geo Con Multi-auger

Solidification & Stabilisation In Situ Technologies Time –Intensive (but slow) Costs (In situ) –Solidification/Stabilisation £ per m 3 (surface mix) £110 – 170 per m 3 (deep auger) Resources –Plant - reagent mixing and auger Application Range –Inorganics (metals, non-metals, cyanides) –asbestos –PCB, PAH –Oil (Direct Chemical Reaction (DCR) method (hydrophobic submicron CaO particles)

Solidification & Stabilisation In Situ Technologies 4. Vitrification (ISV) (currently pre-commercial) Demonstration Process Electrode heating 1600C C Molten zone expands downwards Organics oxidised hood collects gas emissions Long cooling periods Soil volume reduction Costs and availability –Geosafe Corp –Minimum £100K

Example Solidification & Stabilisation Site –Former Scrap-yard Contamination –cadmium, zinc, lead –PCB Remediation Method –Ex situ Solidification & Stabilisation (Cement, PFA, proprietary reagent) Performance –99% reduction of leachable contaminant levels Time –28 days Cost –£50 per tonne

Solidification & Stabilisation Example Vitrification Site –Naval Dockyard, Chatham Contamination –Asbestos –Lead, arsenic, mercury Remediation Method –Ex situ Vitrification (pretreatment, grading, barge shipment) Performance –> 95% reduction of leachable metals –asbestos completely immobilised Time –months (240 tonnes/d) Cost –estimated. > £500 per tonne