aalborg universitet surfactants as enhancement of in situ
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Aalborg Universitet
Surfactants as enhancement of In Situ Alkaline Hydrolysis (ISAH) of pesticide DNAPL
Results of bench and pilot scale field tests
Muff, Jens; Søgaard, Erik Gydesen; Bennedsen, Lars R.; Rügge, Kirsten; MacKinnon, Leah ;Durant, Neal; Pennell, Kurt ; Bondgaard, Morten
Publication date:2015
Document VersionAccepted author manuscript, peer reviewed version
Link to publication from Aalborg University
Citation for published version (APA):Muff, J., Søgaard, E. G., Bennedsen, L. R., Rügge, K., MacKinnon, L., Durant, N., Pennell, K., & Bondgaard, M.(2015). Surfactants as enhancement of In Situ Alkaline Hydrolysis (ISAH) of pesticide DNAPL: Results of benchand pilot scale field tests. Poster presented at AquaConSoil 2015, København, Denmark.
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Pilot scale testing
Conclusion
Surfactants as enhancement of In Situ Alkaline Hydrolysis (ISAH) of Pesticide DNAPL: Results of
bench and pilot scale field tests Jens Muff*1 and Erik G. Søgaard1, Lars Bennedsen2, Kirsten Rügge 3, Leah MacKinnon and Neal D. Durant4,
Kurt Pennell5, Morten Bondgaard6
1Aalborg University, Denmark, 2Rambøll, Denmark, 3COWI, Denmark, 4Geosyntec Consultants, CA & Maryland USA, 5Tufts University, Massachusetts, USA, 6Central Region, Denmark
The research was funded through the NorthPestClean Project by Central Denmark Region supported by EU Life
Background Groyne 42 is a 20,000 m2 former chemical dump site in Denmark contaminated with 100-200 tons of organophosphorous pesticides (OPPs). The majority of contaminant mass is present as sorbed phase and residual DNAPL. The NorthPestClean project was established to determine the effectiveness of using in situ alkaline hydrolysis to treat the DNAPL (Fig. 1). The primary challenge was in situ mixing, establishing sufficient contact between hydroxide and DNAPL and surfactants were tested as 1 of 3 enhancement technologies at bench and pilot scale.
Site and sampling
Initial selection Previous work has identified non-ionic surfactants as the best performing type of surfactants for increasing OPP solubility. Ten non-ionic candidates were tested in bench scale, and equilibrium solubility tests showed that alcohol ethoxylate non-ionic surfactants was superior with respect to increasing OPP solubility compared to the alkaline tap water reference.
Data representation
Bench scale testing
Fig. 1: The alkaline hydrolysis of OPPs.
Fig. 4: Batch equilibrium tests of ethoxylate surfactants at pH 13 with a 10:1 surfactant:DNAPL volumetric ratio. Reaction time was 7 days.
Surfactant enhanced ISAH increased dissolved OPP concentration (x10) and total mass removal was 20-40% higher compared to baseline ISAH.
Fig. 5: Bacth soil tests with contaminated soil / surfactant water ratio of 4 g/mL. No extra DNAPL was added. Results presented are aquesous concentrations and soil removal of four alcohol ethoxylates after 7 days of reaction at pH 13.
Ecosurf EH-9 was chosen for pilot scale testing due to best performance in soil test (lower soil sorption compared to Rhodasurf) and cost of the chemical (3-4 € / kg).
10m
Parameter Compounds
SUM OPPs parathion (EP3), methyl-parathion (MP3), malathion, ethyl-sulfotep
SUM P2 acids O,O-diethylthiophosphoric acid (EP2), O,O-dimethylthiophosphoric acid (MP2)
PNP para-nitrophenol
0
2000
4000
6000
8000
10000
12000
14000
16000
mg
/L
Equilibrium DNAPL tests (30 g/L of surfactants)
SUM OPPs
P2 acids
PNP
0
10
20
30
40
50
60
70
80
0
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Re
mo
val o
f O
PP
s fr
om
so
il (%
)
Co
nce
ntr
atio
n in
wat
er
sam
ple
s (m
g/L
)
Batch tests with soil
SUM OPPs
SUM P2 acids
PNP
Removal
Conducted in close collaboration with:
0
200
400
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1400
mg/
l
TC2 - EP3 (Parathion) Screen 1
Screen 2
Screen 3
Cycle starts
Enhancementstarts
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mg/
l
TC2 - EP2 acid Screen 1
Screen 2
Screen 3
Cycle starts
Enhancementstarts
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mg/
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TC2 - PNP Screen 1
Screen 2
Screen 3
Cycle starts
Enhancementstarts
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Surf
ace
te
nsi
on
(m
N/m
)
Surface tension
2. juli 2013 2. september 2013
TC2: Added surfactant TC3: Reference
Fig. 2: The site is located directly at the waterfront. Residual OPP DNAPL is widespread in hot spots.
Fig. 3: Sampling of site water and soil with visible DNAPL. Over 2½ years, more than 2000 water samples and 1200 soil samples were analyzed in NorthPestClean.
Fig. 6: Pilot testing was completed in 10x10 m test cells (TCs) with TC2 used for testing of surfactants in cycle 3. 1600 kg Ecosurf EH-9 was mixed with extracted water in a 25% solution and added the 60 m3 effective pore volume of the targeted treatment area (TTA) resulting in a concentration of about 2.7%. Baseline ISAH Surfactant-ISAH
Fig. 7: Results showed an increase in EP3 and a slight increase in hydrolysis products up to 1 year after surfactant addition.
Fig. 8: Surface tension analysis showed an equal distribution of surfactant in the TTA of TC2.
* Corresponding author: Associate professor Jens Muff ([email protected]), Section of Chemical Engineering, Department of Chemistry and Bioscience, Aalborg University