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OMV Exploration & Production

Move & More

OMV Austria Exploration & Production GmbH

Sinaia Conference, March 2009

2 |OMV Austria Exploration & Production GmbH, March 2009

Natural Attenuation "in situ"

Natural Attenuation of Hydrocarbons

as a Complement

to "in situ" Remediation Methods

Field Report

by Johann Siwczyk



Contents

How to deal with hydrocarbon (HC) contaminations

Important points in case of "in situ" remediation methods

Site report about a remediation project implementing natural attenuation of HC‘s

Evaluation of natural attenuation (NA)

E

Conclusion and preview



typical procedure in case of HC Contamination

Excavation and Disposal ("on/off site")

(

IN SITU Remediation ("in situ")

Decision-Making

Balancing (Costs and Benefits)the effectiveness of the remediation measures with technical, logistical and financial aspects of the remediation

t



Important conditions for "in situ" remediation methods

Source control (removal of the source as far as practicable)

S

Full hydraulic containment (no downstream impact)

F

Removal of mobile contamination fractions / additional mobilisation (washing out, vibration)

m

There are almost always residual contaminations remaining in underground (stable)

u



Typical attributes of a residual contamination

Trapped in aquifer by cohesion and capillarity / adsorbed to the soil

No free product, no more mobile/mobilizable fractions

No downstream effects on the groundwater

Highly contaminated soil / sediment contamination



Field case - Contamination Data

Contaminated area: 50.000 m2

Soil: sand / silt

Groundwater: depth 2 m, velocity 20 cm / day, eastwards

Contamination: crude oiloil phase plumes with thickness till 10 -30 cm soil contamination 5.000-20.000 mg/kg, depth 2-4 m below t.s.spatially stable, barely soluble



Remediation Data

13 remediation trenches

Total Groundwater pumped out: ca. 5 l / sExtraction well <0,1 mg/l treatment facility → → <0,06 mg/l →receiving water

Oil recovery ca. 1.000 l / monthtotal from 2005 ca. 50.000 l

skimmed of inside the trench → oil tank → pumped into production pipeline

Expected remediation time: decades



prediction for future actual remediation objectives

no downstream effects from contamination plumesremoval of the mobile contamination fractionsno threshold values in the contaminated zone

Residual soil contamination may be expected

further reduction of the contamination by NA possible?

Indicators for Natural Attenuation ?



"Natural attenuation" includes a variety of physical, chemical, or biological processes that, under favorable conditions (within a practicable time frame), act without human intervention to reduce the mass, toxicity, mobility, volume, or concentration of contaminants in soil or groundwater.

These processes include biodegradation (destructive) dispersion, dilution, sorption, and volatilization (non-destructive)

d



36 H2S + 56 CO2 + 32 H2OSulphate reduction8 Toluol + 36 SO4

2- + 72 H+

36 Fe2+ + 7 CO2 + 32 H2OIron reductionToluol + 36 Fe(OH)3 + 72 H+

Chemical reactions using the example of Toluol, C7H8

36 CH4 + 20 CO2

Methanogenesis8 Toluol + 40 H2O

18 Mn2+ + 7 CO2 + 22 H2OManganese reductionToluol + 18 MnO2 + 36 H+

18 N2 + 35 CO2 + 38 H2ONitrate reduction5 Toluol + 36 NO3

- + 36 H+

7 CO2 + 4 H2OOxygen reductionToluol + 9 O2



approx. 0.2 mg/l HC`s1 mg/ l Nitrate reduction

0.8 mg/ l

1 mg/ l

22 mg/ l

11 mg/ l

1 mg/ l

Rate of:

approx. 1.0 mg/l HC`sMethanogenesis

approx. 0.2 mg/l HC`sSulphate reduction

approx. 1.0 mg/l HC`sIron reduction

approx. 1.0 mg/l HC`sManganese reduction

approx. 0.3 mg/l HC`sOxygen reduction

means degradation of:Balance of materials



Fe++



Field Results

Spatial distribution of Eh, O2, NO3-, Fe++, SO4 correlates well

with contaminations and provides evidence of NA

Ongoing hydraulic containment with water extraction results in an inflow of fresh water into contaminated areas and provides a fresh supply of additional HC –attenuating substances

Need for additional support measures (e.g. supplying oxygen, nitrate, sulphate or other suitable nutrients)

n

Need for further investigation about degradation rates and time frames (field test)

t



Conclusions MNA is a necessary and logical complement to the "in situ"

remediation in the final remediation stage

It is not a self-purification process, it needs appropriate support, regulation and control

It is a transition from active remediation measures to natural sorption on the soil (no further action)

s

It is a part of "risk based corrective actions"



Thank You for

your attention.Any questions?

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