Contaminated Land FullScale Remediation Technologies Physical Chemical Thermal

Contaminated Land Full-Scale Remediation Technologies • Physical • Chemical • Thermal

Physical Remediation Technologies • Overview and Principles • Physical Technologies Ex Situ – Soil Washing In Situ – Soil Vapour Extraction – Electro-Remediation • Examples

Physical Remediation Technologies Overview and Principles Soil Washing (Bergmann, Lurgi, Bio. Trol) – intensive, water-based removal of non- and semi-volatile contaminants from soil – washed fractions replaced – contaminated fractions to disposal or further treatment Soil Vapour Extraction (SVE) or Venting – extensive, vacuum extraction of vapour phase from between soil particles; advection for sorbed organics – extracted vapours further treated Electrokinetic Remediation (Geokinetics BV) – electrical current (DC) transports charged (ionic) contaminants towards electrodes – contaminants accumulate at electrode

Physical Remediation Technologies Ex Situ Soil Washing Pretreatment – screening, crushing Washing and Rinsing – Slurrying, attrition scrubbing, ultrasonic treatment – reduced to individual particle size Particle Sizing and Classification (Fractionation) – sedimentation, hydrocyclones, sieving and screening (cf. sand gravel operations) – flotation – flocculants, dewatering – Clean Coarse Fractions – Contaminated Fines - clays, humics Wastewater Treatment – wash water recycle Process works better with coarser soils Soil structure impaired

Physical Remediation Technologies Ex Situ Soil Washing Time – Intensive process (days - weeks) Costs – £ 20 - 160 per m 3 – silt and clay content significant determinant (economic upper limit of 30 - 40%) Resources – plant and power Application Range – most volatile and non-volatile organics – inorganics, heavy metals – Not Asbestos

Example Ex Situ Soil Washing • Site – Canal Sediment, Birmingham • Contamination – Zinc, copper, nickel, chromium – mineral oils • Remediation Method – soil washing – landfill of contaminated fines • Performance – 90 % contaminants concentrated into reduced volume (30% of original sediment) • Time – months due to low capacity of system (10 m 3 /day) • Cost – £ 30 per m 3 including disposal off-site

Soil washing

Physical Remediation Technologies In Situ Soil Vapour Extraction • Established Process (Terra Vac ) – also known as Soil Venting • Extraction Wells – slotted PVC pipe, grouted upper section – depth 1. 5 m to 90 m (Vadose only) – numbers depend on soil permeability – placement critical - short circuiting – Soil surface preparation - compaction, membranes • Infiltration Wells – optional – passive or forced flow – Induced air flow aids bioremediation • Groundwater Abstraction – depression of groundwater table (greater exposure)

Physical Remediation Technologies In Situ Soil Vapour Extraction • Critical Factors – Boiling point / vapour pressure – volatility VOC only (KH > 10 -2 atm. l/mole ) – Subsurface temperature – soil permeability – soil organic matter content • System Monitoring – vapour concentration (pulsed extraction) – mass balance – Oxygen and Carbon dioxide (biodegradation) • Treatment of Extracted Vapours – to atmosphere – Combustion engine – thermal oxidation – GAC adsorption

Physical Remediation Technologies In Situ Soil Vapour Extraction Supplementary Methods • Thermally Enhanced SVE (Steam Stripping) – extends application to less volatile SVOC’s – Steam or hot air injected • Air Sparging – Air bubbled through contaminated groundwater – strips VOC from water • Directional Drilling – contaminated zone geometry – specific positioning of well around existing structures and obstructions • Pneumatic or Hydraulic Fracturing – new channels created

SVE

Physical Remediation Technologies In Situ Soil Vapour Extraction Time – extensive (1 - 2 years) Costs – £ 5 - £ 40 per m 3 – £ 15 – 70 per m 3 (with thermal enhancement) Resources – Power – Emission control equipment Application Range – VOC (some SVOC) – only certain soil types

In Situ Soil Vapour Extraction Example • Site – Service Station • Contamination – 5000 litres fuel beneath road and forecourt – max depth 3 m • Remediation Method – Soil Vapour Extraction (Venting), then bioventing – extraction at 25 - 60 m 3/h • Performance – TPH from 10, 000 mg/kg to 260 mg/kg – half removal by biodegradation (bioventing) • Time – 2 years • Cost – estimated £ 60 per m 3 (includes the bioventing time)

Physical Remediation Technologies In Situ Electrokinetic Remediation • New Full-Scale Process – Patent licence Geokinetics International Inc. • Electrodes – spacing 1 - 2 m – graphite with membrane sheath – electrolyte recirculation and regeneration • Principle – electrokinetic and electro-osmotic movement – Electrode design (recirculated electrolye) – Anions move to anode (+ve electrode) – Cations, metals move to Cathode – Electrolysis of water produces H+ at anode – Acid front sweeps through soil, extracts metals – extensive process (in situ) – intensive (ex situ)

Physical Remediation Technologies In Situ Electrokinetic Remediation • Power Requirement • Low voltage DC 20 - 40 V/m • current at a few Amps/m 2 • 500 k. Wh/m 3 at 1. 5 m electrode spacing • Applicability – Performs well in fine grained, saturated, low-permeability soils ( e. g. clays) – vertical and horizontal process – metal removal – enhanced degradation of organics (Lasagne process) • Considerations – buried metal objects, power cables – soil CEC and alkalinity – safety - hydrogen and chlorine gas generation • Soil Condition – structure and fertility retained

electrokinetics

Chemical Remediation Technologies • Overview and Principles • Chemical Technologies • Examples Ex Situ Soil Washing (with chemicals) Chemical Reactors In Situ Soil Flushing Funnel and Gate

Chemical Remediation Technologies Overview and Principles • Extractive – dissolve contaminant into extractant phase – does not destroy contaminants – Extractants require regeneration – residual extractant left in soil • Destructive – most contaminants are unsuitable (unreactive) – reactivity of soil interferes – reagents may be environmentally unacceptable • Detrimental to Soil Structure and Fertility • Application – few operational commercial processes in use – numerous novel pilot demonstrations

Chemical Remediation Technologies Ex Situ Soil Washing • A Development of the Physical “Soil Washing” process – acids – Alkalis extractant class – chelating agents (EDTA) – surfactants • Benefits – All solid fractions treated – contaminant moved into wash-waters – water treatment possible • Drawbacks – soil structure – residual extractant in soil

Chemical Remediation Technologies Ex Situ Chemical Reactors Ex Situ Solvent Extraction – batch or continuous , single stage or counter-current reactors – extraction into liquid solvent - water/triethylamine – SCF super-critical fluid extractants - CO 2 , propane – vegetable oil regeneration of extractant • Drawbacks – residual solvent contamination – Soil structure • Applications – PCB’s – Viscous, non-VOC – Metals

Chemical Remediation Technologies Ex Situ Chemical Reactors Chemical Dehalogenation (Destructive) • Soil Pretreated • Soil Mixed with reagents – APEG, alkaline polyethylene glycol, (KPEG) • Heated – 100 -180 C for 1 - 5 hours – chlorine removed, glycol ether derivative is formed • Neutralization Time – intensive but limited plant capacity - (months per site) Application – chlorinated contaminants, PCB, solvents, Dioxins Cost – High £ 300 - 500 per m 3

Chemical Remediation Technologies Ex Situ Chemical Reactors Other Potential Destructive Methods • Oxidation – O 3, H 2 O 2 and Ferrous ion, Cl. O 2, Wet Air Oxidation – for PAH, TCE, PCP, phenols , Cyanide • Hydrolysis – reaction with water, better at high p. H – enzymes – for Cyanide, organophosphorus pesticides, • Reduction – Sodium borohydride for many organics – Iron (zero valent) powder for halogenated organics • Polymerization – pre-polymer contaminants (styrene, vinyl chloride)

Chemical Remediation Technologies In Situ Soil Flushing • In Situ version of Soil Washing – no physical mixing • Infiltration and recycle of extractant – shallow soil (galleries, collection channels) – deep soil (extraction well, Pump and Treat) • Mild Extractants – dilute acids, alkalis – chelating agents – surfactants • External Treatment – adsorption, flocculation, biological degradation • Soil Neutralization – must attenuate residual reagents

Soil flushing

Chemical Remediation Technologies Example Soil Flushing • Site – Photographic Paper Factory, Holland • Contamination – 30, 000 m 3 soil with Cadmium (20 mg/kg) – Complex site, buried structures (tanks) • Remediation Method – In Situ Soil Flushing (0. 001 M HCl) – Ion exchange • Performance – Cd reduced to < 1 mg/kg • Time – 1 year • Cost – experience limited, this case £ 90 per m 3

Chemical Remediation Technologies Funnel and Gate (Permeable Reacive Barrier, PRB ) • Barriers (Funnel) – divert groundwater flow – focus contaminants • Reactive Cell (Gate) – Chemical dehalogenation (zero valent Iron filings) – Oxidation • chemical (oxygen precipitation of metal oxides) • biological (bacterial oxidation of BTEX) – Other types of reactive cell • Adsorption (activated carbon) • Biofilter media (biodegradation)

Thermal Remediation Technologies • Overview and Principles • Thermal Technologies • Examples Ex Situ Thermal Desorption Incineration (Vitrification)

Thermal Remediation Technologies Overview and Principles • Ex-situ Method • Fixed Centralized Plant or On-site Plant • Standard Industrial Thermal Processors – cement kiln, asphalt dryer • Soil Destroyed – inert ash Thermal Desorption • organic contaminant moved from solid-phase to gas-phase • relatively low temperatures 400 - 600 C Incineration • organic contaminant degraded (oxidised or Pyrolysed) • very high temperatures 800 - 1200 C Vitrification • extremely high temperatures 1200 - 1600 C

Thermal Remediation Technologies Thermal Desorption • Treatment Train Process – soil pretreatment – desorption with Gas Emission Control – cooling • Kiln – rotary, conveyor, screw – direct or indirect heating • Energy required 2500 MJ per tonne (400 C, 20% moisture) • 300 m 3 gas per tonne • Gas Treatment – Thermal oxidation – Cooling – Scrubbers (acids) – carbon adsorption • Cost – scale dependent £ 50 - £ 300 per m 3 – water content (75% of costs for wet soil > 20% moisture)

Thermal desorption

Thermal Remediation Technologies Incineration • Treatment train process but the main destruction occurs in the kiln • Kiln – Direct Fired Rotary Kiln – Fluidised Bed – infra-red incinerator • Flue Gas – PIC (products of incomplete combustion) – dust – water – acid – metals • Costs – Off-site plant £ 200 - £ 1000 per m 3 (petroleum contaminant) – £ 1000 - £ 5000 per m 3 (for PCB contaminants)

Thermal Remediation Technologies Example Incineration • Site – Oil Refinery, USA • Contamination – 7, 000 tonnes sediment – PCB at 5 mg/kg • Remediation Method – Incineration • Performance – PCB < 0. 9 mg/kg • Time – 2 months • Cost – £ 500 per m 3