1,4-dioxane treatment using electrical resistance heating · • condensate residuals treated by...
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1,4-Dioxane Treatment using Electrical Resistance Heating
Angus McGrath - Stantec [email protected]
David Schroder - Stantec [email protected]
February 2014
Daniel Oberle – TRS [email protected]
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Electricity is directed into the subsurface area.TRS ERH PROCESS
TRS Power Control Unit
TRS ERH PROCESS
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TRS ERH PROCESS
Electricity is directed into the subsurface area.TRS ERH PROCESS
TRS Power Control Unit
TRS ERH PROCESS
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1,4 Dioxane – ERH Projects
0
5000
10000
15000
20000
25000
After ERHAll <50 ug/L
1,4-
Dio
xane
(ug/
L)
Confidential ClientBefore ERH1,000 to 90,000 µg/L
96.5% Removal >99.8% Removal
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1,4-Dioxane and Water Chemistry
Source: Scheider and Lynch, J. Am. Chem. Soc., 65(6), 1943
86
88
90
92
94
96
98
100
102
0 0.2 0.4 0.6 0.8 1
Boi
ling
Poin
t Tem
peat
ure
(°C
)
Mass Fraction 1,4-Dioxane in Water
1,4-Dioxane-Water Boiling Temperature
Azeotrope82% mass fraction
87.7°C
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1,4-Dioxane and Water VLE
Source: Scheider and Lynch, J. Am. Chem. Soc. 65(6), 1943
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.2 0.4 0.6 0.8 1
Mas
s Fr
actio
n 1,
4-D
ioxa
ne in
Ste
am
Mass Fraction 1,4-Dioxane in Water
Linearity at Low ConcentrationsAllows for Modeling by Henry’s Law
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Vapor-Liquid Mass Ratios
Source: Scheider and Lynch, J. Am. Chem. Soc., 65(6), 1943
The V-L Mass Ratio IncreasesSubstantially as 1,4-DioxaneConcentrations Decrease
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Henry’s Law Constant -Experimental Determination
Source: Stantec - Internal R&D Testing Report
0
0.001
0.002
0.003
0.004
0.005
0.006
0.007
0.008
0.009
60 80 100 120 140 160 180 200
H (d
imen
sion
less
)
Temperature (°F)
Henry’s Law – 1,4 DioxaneMethodology
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Henry’s Law Constant - Field Data
1,000 scfm steam1,500 scfm air
ERH Treatment
Condenser
1,500 scfm air1,600 ppb 1,4-Dioxane= 0.12 lb/day
5 gpm condensate94 ug/L 1,4-Dioxane= 0.006 lb/day
Air Out
CondensedSteam
95% of the 1,4-dioxanemass was conveyed intothe vapor phase where itwas effectively removedonto vapor phase granularactivated carbon.
Only 5% of the 1,4-dioxane massremained in the condensed steam.
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Henry’s Law Data –Experimental vs. ERH Field Data
%7.4%10032.281500009.0785.35
785.35
3
=×××+×
×
ftlscfm
gallgpm
gallgpm
95.3% mass transfers to vapor phase4.7% mass remains in condensate
To increase mass transfer to vapor phase…..
Henry’s Law
increase the extracted air flow
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1,4-Dioxane Adsorption
Source: Stantec - Internal R&D Testing Report
10%
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1,4-Dioxane VLE Lab Study - Water
• Start with 1,000 mL of 26 mg/L 1,4-dioxane solution• Boil solution down while collecting L and V samples• Analyze samples using EPA Method 8260B (3 ug/L Detection Limit)
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VLE Lab Study Results - WaterSample 1,4-dioxane
(mg/L)% Water Boiled
% Concentration Reduction
Starting Concentration 26 0% 0%Liquid Sample 1 8.0 13.2% 69.23%Liquid Sample 2 0.285 39.5% 98.9%Liquid Sample 3 0.016 65.8% 99.94%Liquid Sample 4 0.0063 98.7% 99.98%Condensate 1 230 13.2% N/ACondensate 2 36 39.5% N/ACondensate 3 3.4 65.8% N/ACondensate 4 0.585 98.7% N/A
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1,4-Dioxane ERH Lab Study – Soil*
Sample
Steaming Energy Density
(kWh/yd3)
Results1,4-dioxane
(mg/Kg)
PercentReduction
Starting Concentration 0 5.4 0%
20% moisture boiled 75 0.67 87.6%
45% moisture boiled 169 <0.58 >89.3%
80% moisture boiled 300 <0.51 >90.6%
*Soil samples provided by NAVFAC SW
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Design Energy Density Values
0.01
0.1
1
10
50 100 150 200 250 300 350 400 450 500
% 1
,4-d
ioxa
ne re
mai
ning
Design Energy Density (kWh/yd3)Includes specific heat, latent heat and typical heat losses
90% Reduction
99% Reduction
99.9% Reduction
Soil Study
Water Study
Assumes 60 kWh/yd3 specific heat and 35% heat loss to surroundings during ERH. Cost for treatment likely to fall into the range of $150 to $300 per cubic yard.
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Advantages over Pump and Treat
• 90% reduction achieved in 0.5 pore volume removal for ERH vs 20+ pore volume removals for P&T
• Condensate does not contain Fe, Mn or carbonates and it has lower 1,4-dioxane concentrations
• Most of the 1,4-dioxane is conveyed into vapor phase
• Cleanup occurs in several months vs several years
• ERH works great in low permeability soils
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Conclusions• 1,4-Dioxane can be remediated using ERH
• Design Targets:• ~ 220 kWh/yd3 for 90% • ~ 330 kWh/yd3 for 99%• ~ 440 kWh/yd3 for 99.9%
• Majority remains in vapor-phase
• Condensate residuals treated by POTW or easily treated with advanced oxidation processes
• Advantages over pump-and-treat include:• Significantly less water to treat• Lower aqueous concentrations of 1,4-dioxane • Less inorganic and organic interference for water treatment• Cleanup occurs in months rather than years