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Surfactant Flushing of LNAPL Contaminant

Full-Scale Source and Plume Remediation of Golden UST Site:

Treatment-Train Approach

Ben Shiau, Ph.D.Surbec-ART Environmental

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Acknowledgements� Jeff Brammer, Tommy Jones, Glenn Ulrich,

Michiya Susuki, Barry Freeman (Surbec-ART)� Drs. David Sabatini, Jeff Harwell, Robert

Knox (University of Oklahoma)� Mary O�Kelley, Joe Thacker, Dick Oppel

(Oklahoma Corporation Commission)� Dr. John Wilson (US EPA)� Dr. Candida West (University of Oklahoma,

Health Science Center)

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Outline

� Recent Surfactant Flushing Development

� Laboratory Study� Field Test� Conclusions� Future Development

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Recent Surfactant Flushing Development

� Low Surfactant Concentration� Integrated Low Surfactant/

Chemical Oxidation and/or Bioamendment for Complete Site Closure

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Low Surfactant Concentration� Why this approach? Most site owners,

especially USTs and industries, have limited resources for site clean-up efforts

� Improve economics by using low surfactant concentrations (0.1 to 1 wt% versus 3 to 8 wt% in earlier Surfactant Flushing projects)

� Low surfactant challenges: formation of microemulsion (volume reduction, significant change of IFT), greater sorption impact

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Integrated Low Surfactant/Chemical Oxidation or Bioamendment Approach

� Surfactant Flushing is not suitable for dilute plume remediation

� Polishing step: injection of low chemical oxidant (< 1 wt%) and/or bioamendment to polish remaining residual / dilute NAPL plume

� Selection of chemical oxidants and/or nutrients depend on site-specific NAPL and soil properties

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Laboratory Surfactant ScreeningSurfactant system Surfactant

conc.evaluated

wt%

NAPL (TPH)solubility in

Type IIImicroemulsion

mg/L

Equilibratedtime of stable

Type IIImicroemulsion

hr

AOT/AMA/NaCl 1 to 2 440,000 1 � 2

AOT/Calfax16L-35/NaCl*

0.2 to 1 450,000 1 � 2

LubrizolDP/AMA/NaCl

0.2 to 1 400,000 8 - 12

*selected for Golden UST site

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BTEX Degradation with Oxidants

Oxidantsystem

Oxid.conc.

mg/L

Benzenedegrad.

%

Toluene

%

Ethylbenzene

%

TotalXylene

%

H2O2/Fe+2/H2SO4

2,000 92 44 59 45

KMnO4 5,000 8 NA* NA NA

*Benzene only system; Fenton�s Reagent was used at Golden UST site

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RW IW

MEUF

AS

NAPL

PERMEATE STORAGE

DisposalRETENTATE

O/WSeparator

Surfactant Flushing Integrated Process

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Golden, OK UST SiteStarting Point

� Gasoline free phase: thickness on water table 2.7 to 3.3 ft

� Shallow zone (< 15 ft) -silt:benzene, 2,000 to 36,000 µg/L in GW; TPH, non-detect to 345 mg/L

� Deep zone - sand/gravel: benzene, 50 to 3,000 µg/L; TPH, non-detect to 30 mg/L

� Surfactant Flushing Zone: 1.5 acres (22,300 ft2)

silty clay layer

Golden UST geologic cross section

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Free Product Map

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Site Well Layout

LegendDeep Well (DW)Shallow Well (SW)Horizontal WellsMLS

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Carroll�s Grocery � Surfactant FlushRemediation Well Layout Map2/6/02

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2421 3

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Golden UST Site, OklahomaProject Goals� Primary: Remove all free

phase gasoline� Secondary: Significant

decrease in soil and groundwater concentrations (one to two order magnitude)

� Tertiary: Soil and groundwater concentrations to primary drinking water standard

Golden UST Site, OK

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Golden, OK UST SiteApproach / Results

� Low level (< 1 wt%) surfactant/cosurfactantmixture

� 1 PV (190,000 gallons) � 60 days flushing

� Polishing: shallow -- low level chemical oxidation; deep � bioammendments(Phase I); chemical oxidation (Phase II-ongoing)

� Soil and ground water concentrations reduced by one to three orders of magnitude

0.05.0

10.015.020.025.030.035.040.045.0

mg/Kg

MLS-1A

MLS-2A

DW-1A

DW-1B

DW-5A

DW-8A

DW-16A

Benzene Concentration in Soil

Pre-floodPost-flood

0.05.0

10.015.020.025.030.035.040.0

mg/L

MLS-1A

SW-2 SW-5 SW-12

SW-14

SW-33

SW-46

Benzene Concentration in Groundwater

Pre-floodPost-flood

Data collected on 06/27/02

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Golden, OK UST SiteResults vs Goals

� Primary: no visible or instrumental evidence of free phase gasoline in 22 wells after three-month shut-down (3 had trace levels of NAPL)

� > 6,500 gallons gasoline extracted

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Golden, OK UST SiteResults (cont.)

� Secondary: GW--70% to 99% reduction in benzene concentration

� Final Polishing (Chem Oxid-Phase II) to approach MCL (12/02-expected)

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Total NAPL Recovery

0100020003000400050006000700080009000

9/16/01 11/5/01 12/25/01 2/13/02 4/4/02 5/24/02 7/13/02

Date

Gal

lons

of L

NA

PL

Rec

over

ed

Actual recovered Linear prediction

surfactant injection began

Surfactant flush+fresh water chasing

final extraction

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Golden UST Conclusion

� Surfactant Flushing appears technically and economically favorable compared with other technologies

� Significant NAPL mass removal can be achieved by low surfactant concentration approach

� Treatment-train approach -- combination of Surfactant Flushing (source removal) with chemical oxidation and/or bioamendments(contaminant plume polishing) to expedite site closure

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Golden UST Conclusion (cont.)

Economical Comparison! Total project: $712 K! Surfactant Flushing: $569 K; volume

treated = 15,550 yd3; cost = $36 / yd3

! Total project costs (including zones area treated with chem oxid) = $14 / yd3

! Properly designed, economicalAs low as: $25 - 30 / yd3 (LNAPL)

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Current & Future Surfactant Flushing Development

� Potential UST Sites for Low Surfactant Flushing: Oklahoma (2), Arkansas (1), Missouri (1), New Jersey (1)

� Tank Pit Flushing:� Free phase removal

(gasoline & diesel pits)� Love�s Country Store

(OKC, Completed--10/02) Love�s Tank Pit

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Current & Future Surfactant Flushing Development (cont.)

� Approach: low surfactant conc. (1PV)

� Different surfactant systems for gasoline and diesel pits

� Low cost ($10K-20K)� Recycling/ reuse of

recovered water� Compact design

without interrupting the routine activity Tank Pit Effluent

10/16/02

baseline

surfactant flushing