I

University of NebraskaLincoln

Impact of Ethanol Releases: Long-Term Monitoring Results

Roy F. Spalding

Nebraska Ethanol Safety and Environmental Coalition Meeting

Aurora, NEFebruary 4, 2010

Collaborators

Kansas Dept of Health & EnvironmentGreg Hattan

Minnesota Pollution Control AgencyMark Toso

Tom HigginsAdam Sekely

University of Nebraska-LincolnMary Exner, co-PI

Dave Fitzpatrick, graduate student

Ethanol Properties Influencing Fate and Transport

Cosolvency

Surface tension

Specific gravity

Interfacial tension

Phase separation

Bioremediation

Vapor Pressure (mm Hg)

If vapor pressure > 100 mm HgVolatilization from free phase (NAPL)Vaporization of residual

product from dry soilLaw of Partial PressurePtotal = PMTBE + Pother constituents

PMTBE = XMTBE PoMTBE

Pi (mm

Hg)

27–280.8–0.9

2.80.2

0.7–0.8

GasolineConstituent

MTBEBenzeneToluene

Ethylbenzene

Xylenes

% by Volume

11%1%

10%2%

10%

(NSTC, OSTP Report, June 1997)Arulanantham et al., 1999

Iso-octane (49)

Benzene Toluene Ethylbenzene Xylene

BTEX

Wat

er S

olu

bil

ity

(mg

L-1

)

ET

BE

E-B

enze

ne

60,000

0

10, 000

20,000

40,000

30,000

Met

ha

no

l

Eth

ano

l

MT

BE

TA

ME

DIP

E

TB

A

Ben

zen

e

Xyl

ene

50,000

To

luen

e

Infinite

Important when considering unsaturated zone and groundwater plume transport

159 161 535 1,780

9,000

20,000

26,000

50,000

SolubilityW

ater

So

lub

ilit

y (m

g L

-1)

ET

BE

E-B

enze

ne

60,000

0

10, 000

20,000

40,000

30,000

Met

ha

no

l

Eth

ano

l

MT

BE

TA

ME

DIP

E

TB

A

Ben

zen

e

Xyl

ene

50,000

To

luen

e

Infinite

Important when considering unsaturated zone and groundwater plume transport

159 161 535 1,780

9,000

20,000

26,000

50,000

Solubility

0.80.70.60.50.40.30.20.1

10

100

1,000

10,000

100,000BenzeneTolueneXylenes

COSOLVENCY

Volume Fraction of Ethanol in the Aqueous Phase

Aq

ueou

s P

hase C

on

cen

trati

on

(m

g/L

)

Powers (2001)

Surface Tension

70 10 20 30 40 50 60

80

70

60

50

40

30

20

10

Su

rface /

In

terf

acia

l Ten

sio

n

(dyn

e/c

m)

Percent Ethanol in Aqueous Phase

Interfacial Tension

Properties Impacting Ethanol & Gasoline in Capillary Fringe

Powers (2001)

Mixing Ethanol-Blended Fuels with WaterMixing Ethanol-Blended Fuels with Water(Adapted from B.P. Stafford, 2007)(Adapted from B.P. Stafford, 2007)

50 50

50

25

25

75 75

75

ethanol

water gasoline

2 phase field

1phasefield

E10

E95E85

Water Table

gasoline and/or ethanol

water

groundwater

Contaminant spreading in thin layer in collapsed capillary fringe due to decreased interfacial tension.

Predominately anaerobic microbial degradation within the capillary fringe and conversion to methane.

Attenuation in the Capillary Fringe

CH3CH2OH + 1.5 SO4-2 = 2 CO2 + 3 H2O + 1.5 S-2

144 mg SO4-2 /liter consumes 46 mg ethanol /liter

CH3CH2OH + H2O → CH3COOH + 2 H2

CH3COOH → CO2 + CH4

Ethanol Attenuation Mechanisms

Degradation by sulfate reduction:

Fermentation:

~10,000 Gs residual ethanol after product

removal and soil excavation

Balaton, Minnesota

July 28, 2004

~90,000 Gs of d-ethanol released

Balaton, Minnesota

D. Oxygen: 4.3 Years After Derailment

Methane: 2.8 Years After Derailment

Methane: 4.3 Years After Derailment

Benzene: 4.3 Years After Derailment

SOURCE ZONE

C2H5OH: never detected by us

CH3CO2H: 5-100 mg/L

NO3-N: ND in most wells

SO42-: 2 – 3 mg/L

Fe2+: >10 mg/L

Mn2+: ND

H2S: ND

November 22, 2006

~24,877 Gs of d-ethanol released

12,500 Gs recovered

No soil excavation

Cambria, Minnesota

Methane: 0.5 Years After Derailment

Methane: 2 Years After Derailment

SOURCE ZONE

C2H5OH : 120 µg/L – 0.16%

CH3CO2H : <3,090 mg/L

C6H6: ~50 – 900 µg/L

D.O.: < 2 mg/L

SO42-: generally < 5 mg/L

Fe2+: > 10 mg/L

H2S: ND

Tanker held 28,488 Gs of ethanol28,000 Gs were released

South Hutchinson, Kansas

August 31, 2005

South Hutchinson, Kansas

D. Oxygen: 1 Year After Derailment

D. Oxygen: 3.5 Years After Derailment

Methane: 1 Year After Derailment

Methane: 1.3 Years After Derailment

Methane: 2 Years After Derailment

Methane: 2.8 Years After Derailment

Methane: 3.5 Years After Derailment

SOURCE ZONE

C2H5OH : <5 - 240,000 µg/L

C6H6: 100 – 560 µg/L

Acetate: 3.5 Years After Derailment

SOURCE ZONE

H2: 3 – 50 nmoles

Fe2+: >10 mg/L

Mn2+: ND

H2S: usually ND

NO3-N: <1.5 mg/L

SO42-: ~45 – 100 mg/L

Ethanol accumulates & persists in the collapsed capillary fringe (CF) and some may be released to gw after 2 years.

Buoyant ethanol (sg = 0.79 g/cc) floats above the water table.

A protective biofilm coating develops around the ethanol delaying anaerobic degradation and production of methane.

Ethanol concentrations may remain toxic to microbial attenuators within the envelope.

Methane continues to be produced years after the release.

Observations of and Explanations for Ethanol’s Unconventional Behavior

Hypothesis for Ethanol’s Persistence in the Source Zone

A controlled ethanol release test site with about 10 feet to groundwater is needed.

The site should be fully instrumented with volatile traps, gas probes, lysimeters, neutron probe tubes, down-hole camera tubes, and multilevel samplers.

The study will focus on reactions in the CF.

Concentrations of ethanol, methane & hydrogen will be measured routinely by students.

Geoprobe™ cores and biotraps will be used to monitor changes in the microbial community as indicated by chemical indicator changes.

The site will allow improved quantification of the ethanol leached to the CF and its persistence in the CF.

Future Research

AcknowledgementsAcknowledgements

Bruce Bauman, API

John Landwehr, Pinnacle Engineering

Shane Jensen, UNL

Nebraska Ethanol Board

Thank You!

rspalding1@unl.edu