IHA/pm 1

Site remediation

Overview of site remediation techniques

Typical application

Pros/cons

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In – situ treatment

• Where: • Close to / under buildings

• Deep contaminations

• At suitable geology – sand/gravel is best!

• Important aspects:• Physical/chem. properties of chemical (phase

distribution)

• Geology

• Biodegradability of chemical

Determine (potential) transport

When excavation is difficult

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E.g. oil pollution

• Phase removal?• Biological treatment (in situ / of removed phase)?

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The typical approach

1: Initial hot-spot treatment: Suction pipes for free phase (2 – 3 m deep): water + air. Coalecence for free phase + GAC/oxidation

2: Mapping of geology and contamination distribution. Strategy for final treatment.

3: Final treatment (Biological methods, ventilation, ?). Typical operation for 4 – 6 years.

4: Monitoring & control phase.

IHA/pm 5

Strategy – remediation method

Phase (water / gas) extraction + treatment

In situ: destruction

Mass removal:

Mobility reduction (water & air) or fixation in solid phase

Chemical oxidation

Natural /stimulated biodegradation

Vadose zone: Vacuum ventilation, steam stripping, termal desorption, forced leaching.

GW zone: Pumping, In well stripping, sparging.

(e.g. precipitation of metals)

IHA/pm 6

In situ methods – vadose zone

• Natural decomposition • Stimulated biological soil treatment • Soil vapour extraction (vacuum ventilation) *• Forced leaching (*)• Heat enhanced stripping *

• Chemical oxidation (O3 , KMnO4 ..) *

• Phyto remediation• Immobilisation

Alternative. Doing nothing – natural decomposition, leaching…

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In situ methods – ground water zone

• Groundwater pumping and treatment *• In well treatment (stripping) *• Sparging (air, ozone, Bio) *• Biological methods (bioaugmentation, reductive

dechlorination) *• Chemical oxidation *• Reactive walls (Fe0) *

Clay soil: + fracturing (hydraulic / pneumatic)

Combination of methods!

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Control / remediation:Remedial pumping / “Pump & treat”

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Treatment of extracted liquid

• NAPL phase separation (coalescence) petrol, PCE..• Dissolved organic matter:

• Biological treatment. Biological filters (phenols, oil, cyanide, … )

• Chemical oxidation. Ozone, H2O2 (Fenton reagent), KMnO4, …

• Small concentrations. GAC filtration

• Heavy metals: precipitation (pH + complexing agents)

Treated water. Re-infiltration or to sewer

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Vadose zone + volatiles + sand:

Vacuum ventilation

• In unsaturated zone - typical for small quantities of chlorinated solvents og light hydrocarbons

• Initial effect, but then slow. Takes long time to have significant mass removal.

• (cheep alternative: passive ventilation – barometric differences driving force.. )

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Vacuum ventilationon/off operation – rebounce:

Time

Con

cent

ratio

n

Fro

m w

ww

.avjinfo.dk T

ekn

ik & ad

m n

r 4/2003

IHA/pm 12

Near GW table + volatiles + sand:

Air sparging

“Rule of thumbs”:

• If KH > 0.01 (BTEX KH = 0.1 – 0.2 , MTBE KH = 0.02)

• Potentially 90 % mass removal (in sand)• Vacuum flow 2 x sparge flow

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In well stripping

• Intermittent operation to avoid same water drawn as infiltrated.

• 0 – 5 m3/h per filter• 10 – 20 % quick

removal (mass removal) then slow biological process

• Nutrients can be added.• Radius of influence 2 –

3 m

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Treatment of extracted air

Organic chemicals: • Biological treatment in filters (bark, compost.. For

somewhat water soluable compounds)

• Incineration (organic matter in high concentrations)

• GAC filtration (non-polar substances)

• Heavy metals (As, Hg): GAC absorption

IHA/pm 15

GW plume:

Permeable reactive barriers

Literature:

“Design guidance…” A.Gavasker et al, 2000, US Air force recearch lab.

“Economic analysis of ..PRB..” US EPA , 2002.

Fe (o)

KMnO3

GAC

• Hot Water Flushing

• Steam Enhanced Extraction, SEE

• Electrical Resistivity Heating, ERH

• In Situ Thermal Desorption, ISTD

• Radio Frequency Heating, RFH

hotspot:

Thermally enhanced methods

(Smith et al. 1994)

150 200 250 300

PC

Bs,

Dio

xin

s

Naphth

ale

ne

Merc

ury

Vapor pressure with temperature

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500

400

300

200

100

Benz(a)pyrene

Fluorantene

Phenantrene

PCB’s

NafthalenePhenole

XylenePCE, Toluene

TCEBenzene

TCA

Ho

t W

ater

Flu

shin

g

Temperature oC

Ste

am S

trip

pin

g, S

EE

Rad

io F

req

uen

cy H

eati

ng

, RF

H

Th

erm

al C

on

du

ctio

n, I

ST

D

Ele

ctri

cal H

eati

ng

, ER

H

Hot Water Flushing

Steam stripping (SEE) e.g. “Outside – in” approach

Steam stripping (SEE)

“Inside out” design

ElectrodeExtraction well

Electrode

Electrical Heating, ERH

Energy consumption (kWh/m3)

Initial water content

100 % 80 % 10 % 0 %

Heating to 100 ºC, wet 80 61 47 43

Heating to 100 ºC & evaporating all porewater

299 171 69 43

Heating to 200 ºC347 219 117 91

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Biodegradation, e.g.:

Reductive dechlorination

• What: destruction of chlorinated org. solvents(PCE, TCE, VC…)

• Where: in GW zone. At hotspot and in plume.porous soil (contact)

• How: anaerobic biological process• Bioaugmentation. Supply of dehalococoides bacteria• Decomposition process: PCE – TCE – DCE - VC – Ethylene

• The chlorinated organic substance acts as electron acceptor (like O2). The (Electron) Donor must be supplied: H2 .

• anaerobic conditions must be created. Reasonably fast (months / year)

IHA/pm 25

Degradation of chlorinated solvents

ReductiveDehalogenation

Anaerobicoxidation

Aerobicoxidation

Aerobiccometabolism

PCE +TCE + +Dichlorethylene + + + +Vinylchloride + + + +Trichloroethane + +Dichloroethane + + +Chloroethan + +Tetrachloremetha. +Trichloromethane + +Dichloromethane + + +

Boettcher & Nyer, In Nyer et al (2001) In situ treatment technologies, Lewis publishers.

Feb. 2006 IHA/pm 26

Strongly reducing

PCE TCE DCE VC Ethene

AerobicCH4 mv.

AerobicStrongly reducing

Bioaugmen-tation

Dehalococcoides

Sequential redox environment

In real life!

IHA/pm 27

In real life: PCE and TCE in aquifers

VadoseZone

Flow

Chlorinated SolventsCo-disposed withsubstrates (e.g., BTEX,isopropanol, acetone,etc.)

Type I Zone: Added Substrates -High Dechlorination

Rates

Type II Zone: Natural Substrates -

Moderate to LowDechlorination

Rates

Type III Zone: No Substrates -

Low DechlorinationRates

Strongly reducingAerobic

IHA/pm 28

E = Excellent, G = Good, P = Poor

In-situ chemical oxidation - oxidants and contaminant susceptibility

Activated persulfatePersulfatePermanganate

Fenton:H2O2 + Fe O3

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Fentons reagent (Fe + H2O2)

Trailer with H2O2

Injection probes

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Tank with O2

Injection probes

Health issues

Photos taken by:

Watertech, DK

Ove Arkil, DK

Ozone oxidation

Feb. 2006 IHA/pm 31

Case: Remediation of dry cleaning facility By: NIRAS A/S

Dry cleaning facility in Odense, Denmark

Contaminant characteristics:

Soil: Up to 50 mg/kg DW PCE

Groundwater: Up to 58 mg/l PCE

Soil vapor: Up to 2.000mg/m3 PCE

Contaminant mass estimated to 100 kg PCE

Geological characteristics:

Moraine clay with interbedded layers of sand

Site location

IHA/pm 32

1-10 mg/ m3

> 100 mg/ m3

10-100 mg/m3

Getting the overview – making the model

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Groundwater contamination

Dry cleaning facility

Source area >10.000 g/l

1.000-10.000 g/l1-1.000 g/l

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B1 B2 B3

Geological logs

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Sandy zones

Water table

Moraine clay

B3

Conceptual model

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1,9

Uncontaminated soil

Water table

4,2

1,5

Contaminated soil

10,44

6,6

9,41

11,47

6,58

8,53

8,35

8,99

6,02

9,46

m b.s. Average: 9 g KMnO4 / kg soil

Majority of NOD originates from oxidation of natural organic matter

Treatability study: Natural Oxygen Demand (NOD), g-KMnO4/kg

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Laboratory results

• Average diffusion 3 cm per 50 days ~ 20 cm/year

Oxidant

Transparent jar

Intact core

Laboratory setup

• Intact cores, 20 cm

Treatability study: Diffusion into clay matrix

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Remediation concept

Pea gravel and KMnO4 backfilled

Excavation of 25% in source zone

• Excavation of 25 % of the source zone (400 m3 soil)

• Chemical oxidation in source zone and adjacent soils

• Mixture of pea gravel and KMnO4 backfilled

• 12.000 kg KMnO4 (s) installed

• System installed for further addition of liquid oxidant (NaMnO4)

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Dissolved contamination

Moraine clay with sandy zones

PCE diffused into matrix

Concept: Installation of permanganate in fractured clay

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Excavation and installation of KMnO4

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Excavation and installation of KMnO4

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Installation of a mixture of KMnO4 and pea gravel

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Injection wells in source zone

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Monitoring

• PCE

• KMnO4

• Conductivity

• Cl-

• Color

IHA/pm 45

Dry Cleaning facility

Groundwater flow

6 MonthsGroundwater

flow

12 Months

Dry Cleaning facility

A1

Dry Cleaning facility

Groundwater flow

3 Months

Distribution of oxidant

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46

110

140

240

April 2003

[µg PCE/l]

-69%110350M1.3

130

330

1800

January 2003

[µg PCE/l]

+385%630M1.5

-48%170M1.2

-99%11M1.1

ChangeNovember 2003

[µg PCE/l]

Well

Clean up efficiency (water samples)

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Permanganate in soil

Feb. 2006 IHA/pm 48

Fractures in till clay

From lecture by Knud Erik S. Klint, GEUS. At ATV meeting Vingsted 2006

Feb. 2006 IHA/pm 49

Makroporezones in moraine till

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0

1

2

3

4

5

6

7

8

9

10

1,E-09 1,E-08 1,E-07 1,E-06 1,E-05 1,E-04

HYDRAULIC CONDUCTIVITY (m/s)

DE

PT

H (

m)

Serie1

Makropore zonerMakropore zonerMacropore zone 1 Oxidized, no CaCO3, many biopores

Makropore zone 2 Oxidized, CaCO3 rich

Makropore zone 3 Reduced, CaCO3 rich

Bulk hydraulic conductivity (fractures + matrix)

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LNAPL- distribution in clay till. Location Ringe, Fyn.

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Hydraulic fracturing - principle

1) Drill well, Insert casing

2) Displace drive point – expose borehole

3) Notch the borehole (cut a fracture)

4) Propagate fracture with slurry and fluid

From: http://www.frx-inc.com/createfracture.html

Feb. 2006 IHA/pm 53

Contaminatedarea

Fracturing & stimulation

From: Bertil Nielsson et al “In-situ oprensning af organisk forurening I moræneler”, ATV vintermøde 7/3 07.

IHA/pm 54

From: C.E.Riis & A.G.Christensen “Pilotforsøg med pneumatisk frakturering” ATV Vingstedmøde, 2006

Pneumatic fracturing