BLOW OUT OF TRECATE 24 CRUDE OIL WELL: HOW BIOREMEDIATION
TECHNIQUES ARE SOLVING A MAJOR ENVIRONMENTAL EMERGENCY IN A
VALUABLE AGRICULTURAL AREA (Trecate, ITALY)
D. Arlotti1, G. Andreotti2, G. Filauro1
1 Foster Wheeler Environmental Italy2 Eni Agip - Divisione Esplorazione e Produzione
Eni Divisione Esplorazione e ProduzioneAgip
BACKGROUNDThe Incident
• Crude oil well blow-out occurred on February ‘94
• Approximately 12,600 m3 of light sweet crude, 1,000,000 m3 of natural gas and 1,000 m3 of water released to the environment
• Most of the volatile and soluble hydrocarbons flashed during blow-out
• Deposited over 5-Km2 of intensely cultivated agricultural lands
• Deposition influenced by prevailing wind direction to south and south west
Eni Divisione Esplorazione e ProduzioneAgip
BACKGROUND
• A large portion of the oil was retained on and in sandy silt surficial unit to 50 cm
• Vertical migration to subsoil and water table occurred through the sandy gravel subsurface and through infiltration pits used in rice irrigation
• Seasonal fluctuation of the water table level (about 5 m) due to irrigation
• Blow-out occurred when water table was low
• Ground water not used for human consumption
Eni Divisione Esplorazione e ProduzioneAgip
Trecate 24 Well Blow-Out Eni Divisione Esplorazione e Produzione
Agip
Crude Oil Fall-OutEni Divisione Esplorazione e Produzione
Agip
EMERGENCY RESPONSE
• Containment of oily areas and spreading prevention
• 9,350 m3 of free oil were recovered using pumping and vacuum trucks
• Clean-up of the irrigation network
• Clean-up of the Trecate town
Eni Divisione Esplorazione e ProduzioneAgip
EMERGENCY RESPONSEOil recovery from impacted fields
Eni Divisione Esplorazione e ProduzioneAgip
MONITORING PLAN
SOIL220 sampling pointsFrequency: every 3 months
SURFACE WATER27 sampling pointsFrequency: monthly
GROUNDWATER30 sampling pointsFrequency: monthly
AIR8 stations (reduced to 4 after 3 months)Frequency: continuos
BIOLOGICAL EFFECTS- Plants- WildlifeFrequency: 2 campaigns per year
Eni Divisione Esplorazione e ProduzioneAgip
REMEDIATION STRATEGYEnvironmental Constraint
• Authorities and farmers associations requested impacted soil to be remediated without altering or changing its agricultural and biological properties
Bioremediation was selected as remediation approachBioremediation was selected as remediation approach
Eni Divisione Esplorazione e ProduzioneAgip
REMEDIATION STRATEGYSurficial Soil
Eni Divisione Esplorazione e ProduzioneAgip
ZONE 1 - Surface 700 haTPH < 50 ppmMonitoring - Normal AgriculturalOperations w/out Harvesting
ZONE 2 - Surface 480 haTPH 50 - 10,000 ppmLandfarming; Repetition frequencydepending upon Pollution degree
ZONE 3 - Surface 40 haTPH > 10,000 ppmIntensive Landfarming.In the most polluted Area (13 ha)Soil Excavation andEx-Situ treatment in biopiles
REMEDIATION STRATEGYSubsurface Soil
• Contaminated vadose zone soil covering 12,5 ha addressed by Bioventing
• Phase-separated hydrocarbons (PSH) floating on the water table addressed by Bioslurping
• Dissolved-phase hydrocarbons addressed by Natural Attenuation
Eni Divisione Esplorazione e ProduzioneAgip
LANDFARMINGResults
• Treated Surface: 1,200 ha
• Treatment Start-up: September 1994
• January 1995: 93 % of land returned to agriculture
• January 1998: 1,175 ha returned to agriculture (98 % of the initial impacted surface)
• Observed hydrocarbons reduction from concentration greater than 10,000 mg/kg to approx. 50 mg/kg
Eni Divisione Esplorazione e ProduzioneAgip
LANDFARMING ACTIVITIESEni Divisione Esplorazione e Produzione
Agip
BIOPILEConstruction Features
• Two similar Biopiles constructed
• 27,000 m3 of contaminated unbulked soil treated (scraped from 13 ha)
• 20 % by volume of bulking agent added
• Dimensions 50-m x 150-m x 3-m
• 132 internal monitoring locations each Biopile
• Approximately 100 multi-depth soil sampling locations each Biopile
Eni Divisione Esplorazione e ProduzioneAgip
BIOPILE - Isometric
Meters
APPROXIMATE GRAPHIC SCALE
0 5 10 15 20 25
TYPICAL CONFIGURATION OF 0.55m LEVEL
TYPICAL CONFIGURATION OF 1.10m LEVEL
TYPICAL CONFIGURATION OF 1.65m LEVEL
TYPICAL CONFIGURATION OF 2.20m LEVEL
TYPICAL CONFIGURATION OF 2.75m LEVEL
TYPICAL CONFIGURATION OF 3.30m LEVEL
Eni Divisione Esplorazione e ProduzioneAgip
BIOPILEConstruction Activities
Eni Divisione Esplorazione e ProduzioneAgip
BIOPILEConstruction Activities
Eni Divisione Esplorazione e ProduzioneAgip
BIO
PILE
Average P
rocess C
ontrol Data S
umm
ary
0 10 20 30 40 50 60nov-95
dic-95
gen-96
feb-96
mar-96
apr-96
mag-96
giu-96
lug-96
ago-96
set-96
ott-96
nov-96
dic-96
gen-97
feb-97
mar-97
apr-97
mag-97
giu-97
lug-97
DA
TE
TEMPERATURE (c) / MOISTURE (centibars)
0 2 4 6 8 10 12 14 16 18 20
ST
AR
TU
P
OXYGEN (%)
TE
MP
ER
AT
UR
E (C
)
MO
IST
UR
E (ce
ntiba
rs)
OX
YG
EN
(%)
Eni
Divisio
ne E
splo
razion
ee
Pro
du
zion
eA
gip
BIOPILEOperation and Maintenance
• Remediation performance controlled through laboratory analysis of soil samples (quarterly) and through soil gas respiration testing (monthly)
• Air, water, nutrients and heat added where needed (on zone - lift specific basis)
• Continuos and automatic process data management
Eni Divisione Esplorazione e ProduzioneAgip
BIOPILEResults
• Treatment Start-up: November 1995
• Original average TPH concentration in soil: 20,000 mg/kg
• After 18 months residual hydrocarbon content in soil around 5 % of original concentration (resolved compounds)
• Significant total PAH reduction (up to 4-rings)
• Authorities agreed to redistributing treated soil on fields of provenance
Eni Divisione Esplorazione e ProduzioneAgip
BIOPILETPH Reduction
B IO P IL E 1 T P H C O N C E N T R A T IO N (m g /K g )
0
2 00 0
4 00 0
6 00 0
8 00 0
10 00 0
12 00 0
14 00 0
16 00 0
18 00 0
20 00 0
-1 0 1 2 3 4 5 6
Q U A R T E R O F O P E R A T IO N
HY
DR
OC
AR
BO
N C
ON
CE
NT
RA
TIO
N
(mg
/Kg
)
T P H re s o lv e d u n re s o lv e dTPH FITTED RES O L V ED FITTED UNRES O L V ED FITTED
A S Y MPTO TE TPH = 5 8 6 2 A S Y MPTO TE RES O L V ED = 8 4 8 A S Y MPTO TE UNRES O L V ED = 5 0 1 2
P re -B a se l in e
PRETREATMENT
Eni Divisione Esplorazione e ProduzioneAgip
BIOPILEPAH Reduction
B IO P IL E 1 P A H C O N C E N T R A T IO N (m g /K g )
0
10
20
30
40
50
60
70
80
90
100
110
0 1 2 3 4 5 6
Q U A R T E R O F O P E R A T IO N
To
tal P
AH
CO
NC
EN
TR
AT
ION
(mg
/Kg
)
M E AS U R E D C O N C E N T R AT IO N
F IT T E D C O NC E NT R AT IO NS
AS YMP T O T E = 27 .73 ppm
Eni Divisione Esplorazione e ProduzioneAgip
BIOVENTING
• Pilot test performed in two locations to design full-scale system
• Radius of air injection-influence, pressure/airflow relationship and in situ biodegradation rate measured
• Full scale system layout covers 12.5 ha at a depth of approx. 12.5-m
Eni Divisione Esplorazione e ProduzioneAgip
BIOVENTING
• Full scale system includes 26 air injection 4” wells, 5 air injection pumping stations, piping and 36 in situ soil vapor monitoring clusters spaced throughout bioventing area
• Vapour monitoring (O2, CO2 and VHC) and in-situ respiration tests performed on periodic basis
Eni Divisione Esplorazione e ProduzioneAgip
BIOVENTINGResults
• At startup in November 1995 entire area devoid of oxygen (less than 5%) and initial average estimated biodegradation rate approx. 5 mg/kg-soil/day
• Within two weeks of air injection oxygen concentrations increased to 10-20%
• Biodegradation rates in highly impacted areas have increased over time during 1996 and 1997, some as high as 80 mg/kg-soil/day
Eni Divisione Esplorazione e ProduzioneAgip
BIOVENTING Results
• Increase in rates probably a function of enhanced microbial acclimation and relatively new release
• Oxygen demand varies significantly with patchy crude oil subsurface distribution
• System is still running and a reduction of thebiovented area is foreseen in 1998 (almost 30% of original area)
Eni Divisione Esplorazione e ProduzioneAgip
BIOVENTINGAir injection pumping station
Eni Divisione Esplorazione e ProduzioneAgip
PSH RECOVERY• PSH found to float on top of water table during
minimum level period (November through March)
• Approx. 400 m3 of PSH estimated initially
• Pilot test performed to evaluate oil recovery options (skimming, vacuum enhanced pumping and Bioslurping)
• Vacuum enhanced recovery system adopted and built
Eni Divisione Esplorazione e ProduzioneAgip
PSH RECOVERY
• Full scale system covers 3 ha and includes 1 vacuum source and 6 extraction wells equipped with downhole pumps
• System is running only during minimum water table level when PSH are recoverable
• Mobile equipment (Bioslurper) is used when needed
Eni Divisione Esplorazione e ProduzioneAgip
NATURAL ATTENUATION• Dissolved phase hydrocarbon plume was found
as a result of PSH distribution
• Groundwater monitoring network ofpiezometers was designed and built across area of interest
• A protocol for monitoring intrinsic bioremediation implemented (sampling and analysis plan)
• Indicator parameters selected
Eni Divisione Esplorazione e ProduzioneAgip
NATURAL ATTENUATIONResults
• Dissolved oxygen, nitrates, nitrites, sulfate, ferrous iron, methane, alkalinity, oxidation-reduction potential, pH and conductivity monthly monitored over a two year period
• Good relationship between dissolved hydrocarbon plume and intrinsic parameters distribution observed
• No detectable dissolved phase plume observed in downgrading sentinel wells
Eni Divisione Esplorazione e ProduzioneAgip
NATURAL ATTENUATIONResults
• Dissolved hydrocarbon plume appears to be stable, not expanding and intrinsically controlled via aerobic and anaerobic bacterial degradation
• Modeling of the phenomenon using BIO F&T is currently carried out
Eni Divisione Esplorazione e ProduzioneAgip
CONCLUSIONS• Soil, Subsoil and groundwater were impacted as a
consequence of the blow-out
• Use of conventional remediation methods (i.e.. soil excavation and disposal in landfill, water pump & treat, ect.) would have involved:
�extremely large soil movements�change of soil characteristics for agriculture�overall costs higher than bioremediation�heavier environmental impact
Eni Divisione Esplorazione e ProduzioneAgip
CONCLUSIONS
• Use of an integrated bioremediation approach after 4 years has lead to the reclamation of the original impacted area
• Complete release of the area appears possible based on Risk Assessment approach which is being negotiated with the Authorities
Eni Divisione Esplorazione e ProduzioneAgip
Related Papers presented at the Fourth International In Situ and On Site Bioremediation
Symposium (New Orleans, 1997)
• Comparison of Biopile Respiration Rates and Observed Reductions in Soil TPH Concentration (H.J.(H.J. ReisingerReisinger and others)and others)
• Demonstrated Cost Effectiveness of Bioventing at a Large Crude-Oil Impacted Site (H.J.(H.J. ReisingerReisinger and others)and others)
• Natural Attenuation of a Petroleum Production Well Release in Northern Italy (C.D.(C.D. FintonFinton and others)and others)
• Degradation of Saturated and Polycyclic Aromatic Hydrocarbons and Formation of Their Metabolities in Bioremediated Crude Oil-Containing Soil (A.(A. PortaPorta and others)and others)
• Evaluation of Optimum Hydrocarbon Degradation Conditions: ABiotreatability Study (D.(D. TamburiniTamburini and others)and others)
Eni Divisione Esplorazione e ProduzioneAgip