Biodegradation of MTBE and BTEX in a Biodegradation of MTBE and BTEX in a Full-Scale Reactor down to ppb Levels Full-Scale Reactor down to ppb Levels after Inoculation with a MTBE Degrading after Inoculation with a MTBE Degrading CultureCulture

Erik Arvin, DTU EnvironmentChristopher Kevin Waul, DTU EnvironmentRasmus Krag, Jord·Miljoe A/SCharlotte Juhl Søegaard, Jord·Miljoe A/SJeppe Lund Nielsen, Section of Biotechnology, AAU

Natural and stimulated biological degradation –

Processes and microbiology

ATV Soil and Groundwater

21. April 2010

ContentContent

Contamination with MTBEGuidelinesMTBE propertiesBiological degradation of MTBEDevelopment of MTBE cultureFull scale MTBE treatment plantMTBE and BTEX removal MicrobiologyPerspectivesConclusions

Oil/gasoline spillOil/gasoline spill

Oil, air, waterSoil-zone

Free oil

Groundwater Dissolved hydrocarbonsBTEXN

Aromatic hydrocarbons from gasoline, BTEXNAromatic hydrocarbons from gasoline, BTEXN

GuidelinesGuidelines

Drinking Water Requirements (DK)Drinking Water Requirements (DK)µg/Lµg/L

Benzene: 1Alkylbenzenes: 1Naphthalene: 2TPH (Tot. Petroleum Hydrocarbons): 5MTBE (Methyl tert. butyl ether): 5Spec. phenols: 0.5

Groundwater & surface water requirements for Groundwater & surface water requirements for MTBE (DK)MTBE (DK)

Groundwater: 5 µg/LSurface water: 10 µg/LRain water, sewers: 10 µg/L

MTBE is a gasoline additive!MTBE is a gasoline additive!

Ether compound

Lead replacement

Improves air quality

Adds oxygen to fuel

Adds octane to fuel

Chemical structure of methyl tert-butyl ether

Cleaner burning fuel

Properties of MTBEProperties of MTBE

CH3

CH3

CH3

CH3O C

Molar weight: 88Solubility, water: 50.000 mg/LHc: 0.022log Kow: ca. 1log Koc: ca. 1Vapour pressure: 245 mm Hg, v. 25 °C

Biodegradability of MTBEBiodegradability of MTBE

MTBE mineralization reactionsMTBE mineralization reactions(F. Finneran and D.R. Lovley, 2003)(F. Finneran and D.R. Lovley, 2003)

Reactions Go (pH 7, 25C)kJ/mole MTBE

Aerobic respirationC5H12O + 7.5 O2 5 HCO3

- + 5 H+ + H2O-3246

DenitrificationC5H12O + 6 NO3

- + H+ 5 HCO3- + 3 N2 + 4 H2O

-3055

Nitrate reductionC5H12O + 3.75 NO3

- + 2.5 H+ + 2.75 H2O 5 HCO3- + 3.75 NH4

+-1951

Fe(III) reductionC5H12O + 30 Fe(OH)3 + 55 H+ 5 HCO3

- + 30 Fe++ + 76 H2O-347

Sulfate reductionC5H12O + 3.75 SO4

- - + 2.5 H+ 5 HCO3- + 3.75 H2S + H2O

-275

MethanogenesisC5H12O + 2.75 H2O 3.75 CH4 + 1.25 HCO3

- + 1.25 H+ -239

Anaerobic degradation of MTBEAnaerobic degradation of MTBE

Probably, it does not occur in most cases. However, anaerobic abiotic hydrolysis may take place.If anaerobic biodegradation takes place, it is probably a very slow reaction.

Aerobic biodegradation of MTBEAerobic biodegradation of MTBE

1. Biodegradation of MTBE as a primary substrate

2. Biodegradation by cometabolism with lowmolecular alkanes and cycloalkanes as primary substrates

MTBE biomass growth rate and growth yieldMTBE biomass growth rate and growth yield

Doubling time: 7-20 days Growth yield: 0.1-0.2 g biomass/g MTBEObservation of no degradation may be due to the very slow biomass growth

Development of the MTBE degrading culture

Batch cultures degrading MTBEBatch cultures degrading MTBE

Submerged biofilter for MTBE degradationSubmerged biofilter for MTBE degradation

Height of column 0.3 mVolume

0.46 L total0.27 L porosity

Filter materialExpanded clay (Filtralite®)1.5 – 2.5 mm

DTU bench scale biofilters for MTBE degradationDTU bench scale biofilters for MTBE degradation

Two columns in seriesHeight 1 m and diameter 10 cmVolume 9.5 L eachFilter material

Expanded clay (Filtralite®)2.5 – 4 mm

Seeded with filter material from small column

Schematics of the MTBE treatment plant Schematics of the MTBE treatment plant with biofilters BF1-BF3.with biofilters BF1-BF3.

On-site MTBE removal in biofilter in FarumOn-site MTBE removal in biofilter in Farum

Oil separator (left) and biofilters (right). Oil separator (left) and biofilters (right).

MTBE removalMTBE removal

1

10

100

1000

10000

0 100 200 300 400 500Time (day)

MT

BE

(u

g/L

)

GW BF1

BF2 BF3

BTEX removalBTEX removal

1

10

100

1000

10000

0 100 200 300 400 500Time (day)

BT

EX

s (u

g/L

)

GW OS

BF1 BF2

MTBE removal kineticsMTBE removal kinetics

Data from Farum plant, Svendborg/Grubbemølle Water Works and DTU bench scale plant

1’st order removal rate constant: k1,v = 1.7-4.4 h-1 (C_MTBE < 2000 ug/L)

Variation in k1,v probably due to differences in specific surface removal area, cultures, etc.

MicrobiologyMicrobiology

Molecular analysis by DGGE analysis has identified a complex community structure in the biofilters. The majority were members of the phyla: Bacteroidetes, Proteobacteria, and Nitrospirae Among the genera identified were Terrimonas and Methylibium petroleiphilum (PM1)Proof of active MTBE degraders will be investigated by microautoradiography and fluorescence in situ hybridization

PerspectivesPerspectives

Extremely efficient and stable MTBE and BTEX removal has been demonstratedThe full scale plant removes MTBE and BTEX to below drinking water and surface water requirementsDetermination of the MTBE removal kinetics allows more credible plant design

ConclusionsConclusions

Successful up-scaling of MTBE removal from lab. scale to full scale biofiltersMTBE removal > 99 %Effluent MTBE ~ 1 ug/L BTEX removal > 99.9 %Effluent BTEX ~< 0.01 ug/LHigh process stabilityk1,v = 1.7-4.4 h-1

Variation in removal rate constant is probably due to differences in specific surface areas in plantsBacterial community composition is complex and under investigation

ACKNOWLEDGMENTSACKNOWLEDGMENTS

Ulrich Gosewinkel Karlson from the National Environmental Research Institute, University of Aarhus, Roskilde, Denmark, provided a mixed MTBE degrading culture for inoculation of the batch cultures that preceded the 10 L lab biofilter that was used for up-scaling. Statoil: We acknowledge very much Statoil for the opportunity to test the MTBE and BTEX removal plant in full scale.