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GROUNDWATER & ENVIRONMENTAL
SERVICES,INC.
Surfactant-Enhanced Groundwater
Extraction for Expedited Remediation David Sheehan, PE, Senior Engineer
Lydia Ross, EIT, Engineering Supervisor Fort Lauderdale, Florida
Our Background
Dave has 17 years of experience at several GES offices, including New Jersey, Massachusetts, and Southern Florida. Dave is a P.E. in 5 states and specializes in equipment specification, technical permit preparation, construction management, oversight of system operations, and international site assessment work.
> BS, chemical engineering – Rensselaer Polytechnic Institute
Lydia has four years experience at the Southern Florida GES office. She specializes in engineering design of remediation systems and overseeing the operation, monitoring, and maintenance of complex remediation systems, including system evaluations and upgrades, advanced troubleshooting, and ensuring permit compliance.
> MS, engineering management – Florida International University
> BS, mechanical engineering – University of Pittsburgh
The Site
Active retail fuel station
Diesel discharge in 2001 and gasoline discharge in 2005
Receptors: agricultural well (4,731-feet away); sensitive habitat (171-feet away); and a surface water body (1,890-feet away)
AOC/COC: Low-level hydrocarbon impacts localized to the active tank field area.
> (See Figures on Next 2 Slides)
Soil Impacts
Groundwater Impacts
Note: Monitoring wells with sampling results installed to total depths of 12 – 13 feet bgs.
Technologies Considered
AS/SVE/Biosparge pilot test conducted – small observed ROI made system installation overly expensive to be practical
Chemical Oxidation could not be safely applied due to proximity to active tank field
Excavation was not practical due to proximity to subsurface features and the impact to an active station
P&T or VEGE not considered to be aggressive enough
Selected Technology
Surfactant Enhanced Groundwater Extraction (SEGE)
Pros
Can be applied just in targeted source area
Minimal initial costs to implement
One-time event for minimal station business impact
More aggressive than GW recovery
Cons
Untested in Miami-Dade County
May not be as aggressive as traditional technologies like AS/SVE
Basis for the Remedial Plan GW concentrations of CoCs in monitoring wells MW-9 and MW-10
were below NADCs, and impacts in CW-1 through CW-4 had historically fluctuated above and below NADCs.
An overall decreasing concentration trend over time could not be illustrated.
An estimated 14.2 pounds of BTEX/MTBE/TBA were estimated to be present in the groundwater and 16.5 pounds in the soil.
Removing the source area contamination would make conditions more favorable for natural attenuation to reduce concentrations in wells CW-1, CW-2, CW-3, CW-4, MW-9, and MW-10.
Due to the limited mass of hydrocarbons remaining at the site, surfactant-enhanced groundwater extraction followed by natural attenuation is the most practical and cost effective remedial option.
Specifics for the Remedial Plan
GES proposed a SEGE event limited to the tank field area to address adsorbed hydrocarbons in the source area that were contributing to the dissolved-phase plume.
An Alternative Technology Acceptance had been granted by the FDEP for the use of Biosolve, a specific brand of non-ionic surfactant. However, GES proposed using EnviroClean’s comparable surfactant product due to EnviroClean’s technical expertise on the topic of SEGE.
GES proposed installing four injection/extraction wells to a depth of 16-feet bgs at the corners of the tank field area.
Application details and a post-monitoring plan were determined.
Challenges A UIC permit was required it would establish a Zone of Discharge (ZOD) as the pH of
EnviroClean surfactant may exceed the secondary drinking water standards.
Because EnviroClean did not have an acceptance letter from the FDEP, Miami-Dade County ERM required submittal of “The PRS Product Application Form” including proprietary surfactant information. GES worked with EnviroClean on this submittal to get approval for the use of the product.
ERM was also concerned because Biosolve had been utilized at another site in Miami-Dade County and left behind potentially harmful nonylphenols. ERM then requested additional sampling to prove nonylphenols were not created as by-products of the surfactant injection.
Two of the ingredients in the EnviroClean product are classified as octylphenols, but nonylphenols are not ingredients in the product.
Additionally the injected surfactant is removed from the subsurface, and Cobalt Theocyanate Active Substances (CTAS) and EPA method SM20 5540C for surfactants as Linear Akylbenzene Sulfonate (LAS) via Methylene Blue Active Substances (MBAS) sampling is conducted to confirm total removal of the EnviroClean product.
Challenges (cont.)
When an acceptable monitoring plan was developed it included sampling immediately before the injection/extraction event, immediately after the injection/extraction event, two weeks following the event, and quarterly for the duration of the Zone of Discharge for the UIC permit. To receive results for all contaminants and potential by-products samples had to be sent to laboratories in three different states as shown:
Method Laboratory Location
EPA Test Method 8260B for BTEX/MTBE/ oxygenates, EPA Test Method 8310 for PAHs, and surfactants via method SM20 5540 C
Xenco Boca Raton, FL
Octylphenols via method WE-MS-0010/GC-MS
TestAmerica West Sacramento, California
Non-ionic surfactants via method SM 5540D
Analytical Services, Inc.
Norcross, Georgia
How Surfactants Work
“By targeting and extracting pooled and sorbed SPH from
within the capillary fringe and upper aquifer zones via [the surfactant injection/recovery] process, the source area can be rapidly and effectively eliminated. The use of surfactant will maximize the effective mass removal and minimize the total generated effluent for the recovery event as well as limit the continued duration of the recovery process.”
Surfactant
= Surface Active Agent Anionic = neg. charge
Cationic = pos. charge
Non-ionic = no charge
Amphoteric = both charges
Credit: EnviroClean
How Surfactants Work (cont.) “The injection of surfactant solution can facilitate contaminant removal by; 1) increasing
contaminant solubility through the formation of microemulsions, and 2) by reducing interfacial tension and increasing the potential for contaminant mobilization through the formation.”
Solubilization
(microemulsions)
Desorption &
Mobilization
Surfactant
Solution
Trapped LNAPL (Hydrocarbon) at Residual Saturation
Soil Grains
Credit: EnviroClean
Selected Surfactant
The EnviroClean Surfactant
“Is a formulation of non-ionic surfactants blended and balanced to be effective on a wide array of hydrocarbons and fats, oils, and grease while maintaining chemical stability at dilution
Is a concentrated formulation designed for versatile and economical applications at various light concentration working dilutions
Is a water based, biodegradable product which contains no builders, caustic, petroleum distillate, d-limonene, or hazardous chemicals”
Credit: EnviroClean
Technical data:
pH (concentrate) 8.5
Melting Point 28.8° F
Boiling Point >200° F
Surface Tension (6%) 31.6 Dynes/cm
Viscosity at 32° F 9 CP
Specific Gravity 1.03
Pounds per Gallon 8.37
Solubility in Water Complete
Ionic Activity nonionic
CMC 400 ppm
EnviroClean is available in:
5-gal, 55-gal, 275-gal, and 330-gal units
Selected Surfactant
The EnviroClean Surfactant
The SEGE Event
Well Locations
Baseline groundwater sampling was performed on August 30, 2010 to obtain background concentrations for CoCs, surfactants and octyphenols.
The first step was to extract 4,000-5,000 gallons of water from the tank field area to attempt to drawdown the water table prior to the surfactant injection.
Following the initial extraction, approximately 5,000 gallons of 2 percent EnviroClean solution was to be injected into wells IW-1 through IW-4, alternating from IW-1 and IW-3 to IW-2 and IW-4 approximately every two hours.
A sample of the surfactant solution to be injected was to be taken and analyzed for MBAS surfactants, CTAS surfactants, and p-tert-Octylphenol.
The solution would be allowed to sit in the subsurface for up to 36 hours to achieve optimal contact time.
Approximately 5,000 gallons of fluid would be recovered from the site
The SEGE Event
The Plan/Preliminaries
DTW, pressure and pH was measured from selected monitoring wells. Groundwater extraction was stopped after 3,500 gallons had been extracted as a maximum
drawdown of only 0.11 feet was observed. Following the initial extraction, approximately 5,110 gallons of 2 percent EnviroClean solution was
injected into wells IW-1 through IW-4, alternating from IW-1 and IW-3 to IW-2 and IW-4 approximately every two hours. The entire injection took approximately 8.5 hours.
The water table rose an average of 0.17 feet per well over the course of the injection event. There was an increase in pH in all injection and observation wells excluding observation wells CW-7 and MW-2 which had no change and observation well CW-3 which had a decrease in pH. Pressure readings were only taken for the first three hours because there was no observed pressure influence on any of the wells.
The following table summarizes the change in the water table and pH from the injection and the amount of time injected into each injection well:
The SEGE Event
Day 1 -- September 13, 2010
Injection Well ID Change in Water Table
(feet)
Change in pH Total Time of
Surfactant Injection
(hours)
IW-1 + 0.19 + 1.06 3.3
IW-2 + 0.17 + 1.16 4.0
IW-3 + 0.16 + 0.84 3.3
IW-4 + 0.20 + 0.11 4.0
On September 14, 2010 the surfactant remained in the subsurface.
On September 15, 2010 the surfactant/groundwater extraction event was conducted.
DTW, pressure, and pH were monitored prior to, and through the extraction event.
A total of approximately 3,000 gallons were extracted from wells IW-1 and IW-2 in a period of 2.7 hours. A total of approximately 3,000 gallons were extracted from wells IW-3 and IW-4 in a period of 1.5 hours.
The average water table drawdown per well was 0.12 feet from start to finish.
There was a decrease in pH in all injection and observation wells ranging from 0.06 to 0.25. There was no pressure influence observed during the extraction.
The SEGE Event
Days 2-3 -- September 14-15, 2010
The laboratory analysis from the September 28, 2010 sampling event indicated octylphenols increased above baseline concentrations which indicates coverage in the target area and confirms distribution of the surfactant in the impacted area.
Throughout the surfactant enhanced groundwater extraction event, the pH ranged from 6.66 to 8.11, which is consistent with the secondary groundwater standards. The pH monitoring results from the September 15 and September 28, 2010 sampling events indicated a pH of 6.44 and 6.42 at MW-1, which is outside of the range for secondary drinking water standards.
The laboratory analysis indicate hydrocarbon concentrations slightly increased in wells CW-1, CW-4, MW-1, MW-2, MW-9, and MW-10 as compared to the baseline sampling prior to the remedial activities. This increase may be attributed to the release of adsorbed-phase hydrocarbons to the dissolved phase. Hydrocarbon constituents are more amenable to biodegradation in the dissolved phase than in the adsorbed phase and this phase change was seen as a positive effect of the surfactant application.
The SEGE Event
Initial Sampling Results
Where We Are Now
Six Quarters of Monitoring Performed
Quarter Sampling performed on:
> February 8, 2011
> May 11, 2011
> August 10, 2011
> November 10, 2011
> February 9, 2012
> August 9, 2012
All BTEX/TBA concentrations are below GCTLs
Octylphenols remain above the baseline concentrations that were collected on September 15, 2010, prior to the remedial injection event, however a strong decreasing trend has been observed.
The pH monitoring results from the February 9, 2012 sampling event ranged from 6.51 to 6.81 in monitoring wells CW-1, CW-2, CW-3, CW-4, MW-1, MW-2, MW-9 and MW-10 which is within the range for secondary drinking water standards.
Where We Are Now Sampling Results – BTEX, Octyphenols, Surfactants, and pH
Octylphenols Concentrations vs. Time
0
500
1000
1500
2000
2500
8/30/10 11/30/10 2/28/11 5/30/11 8/30/11 11/30/11 2/29/12 5/30/12
Date
Oc
tylp
he
no
ls C
on
ce
ntr
ati
on
(u
g/L
)
CW-1 Octylphenols (ug/L)
CW-2 Octylphenols (ug/L)
CW-3 Octylphenols (ug/L)
CW-4 Octylphenols (ug/L)
MW-9 Octylphenols (ug/L)
MW-10 Octylphenols (ug/L)
BTEX Concentrations vs. Time
0
50
100
150
200
250
300
350
8/30/10 11/30/10 2/28/11 5/30/11 8/30/11 11/30/11 2/29/12 5/30/12
Date
BT
EX
Co
nc
en
tra
tio
n (
ug
/L)
CW-1 BTEX (ug/L)
CW-2 BTEX (ug/L)
CW-3 BTEX (ug/L)
CW-4 BTEX (ug/L)
MW-9 BTEX (ug/L)
MW-10 BTEX (ug/L)
Surfactants (CTAS) Concentrations vs. Time
0
2000
4000
6000
8000
10000
12000
8/30/10 11/30/10 2/28/11 5/30/11 8/30/11 11/30/11 2/29/12 5/30/12
Date
Su
rfa
cta
nts
(C
TA
S)
Co
nc
en
tra
tio
n (
ug
/L)
CW-1 Surfactants (CTAS) (ug/L)
CW-2 Surfactants (CTAS) (ug/L)
CW-3 Surfactants (CTAS) (ug/L)
CW-4 Surfactants (CTAS)(ug/L)
MW-9 Surfactants (CTAS) (ug/L)
MW-10 Surfactants (CTAS) (ug/L)
pH vs. Time
5.50
6.00
6.50
7.00
7.50
8.00
8.50
8/30/10 11/30/10 2/28/11 5/30/11 8/30/11 11/30/11 2/29/12 5/30/12
Date
pH
CW-1 pH CW-2 pH
CW-3 pH CW-4 pH
MW-9 pH MW-10 pH
In Summary
SEGE was an untested technology in Miami-Dade and therefore required some additional information for approval.
A one-time event was performed on the site over a span of three days resulting in much less impact to the station than a permanent system install.
3,500 gallons of groundwater were extracted, ~5,000 gallons of 2% surfactant solution was injected, after ~36 hours ~6,000 gallons of surfactant and groundwater were removed from the subsurface.
The site is in PARM and all BTEX/TBA concentrations are below GCTLs.
Octylphenol concentrations show a strong decreasing trend.
GES expects to monitor the site for one additional quarter and then request closure.
Questions?
You may email Dave or Lydia at [email protected]
or
or
Office: 845.532.2157 Email: [email protected] .
