Tools for Predicting DNAPL Removal from Groundwater Using Neutrally Buoyant Co-solvent Flooding Johana Husserl Ana M. Ocampo Glen R. Boyd, Ph.D, P.E. Tulane University, New Orleans, LA. Department of Civil and Environmental Engineering
Outline Background Physical Model Neutral Buoyancy Recommendations for Future Work
Background What are DNAPLs? Dense Non Aqueous- Phase Liquids Bedient et al., 1999. Ground Water Contamination, PTR.
Background Pump-and and-treat Neutral Buoyancy Co-solvent Flooding Use alcohol solution to reduce density of DNAPLs to avoid downward mobilization Investigate well patterns and DNAPL recovery
Physical Model - Objective Design and build 2-D 2 D physical model to investigate neutral buoyant co-solvent flooding Effects of well-patterns Different inclination planes
Physical Model - Approach Design and manufacture 2-D 2 D prototype model Conduct scaling experiments to size and operate 2-D 2 D model Perform material compatibility tests and structural design Manufacture and assemble 2-D 2 D model
Physical Model - Approach Design and manufacture 2-D 2 prototype model ------------------------------------ To identify problems with design
Physical Model - Approach Conduct scaling experiments to size 2-D 2 D model ------------------------------------------ Injection rates/well Locations Use Hexane for material compatibility R E C O V E R Y E F F IC IE N C Y 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0.000000005 0.00000001 0.000000015 0.00000002 SCALING NUMBER 5 SPOT WITHOUT LOSS TO AQUIFER 5 SPOT WITH LOSS TO AQUIFER 2 SPOT WITH LOSS TO AQUIFER 2 SPOT WITHOUT LOSS TO AQUIFER
Physical Model - Approach Perform material compatibility tests and structural design ---------------------------------------------- Identify materials compatible with PCE/alcohol/water Finalize structural design using Stainless steel and glass Lexane and TCE Effects of TCE on Steel
Physical Model - Approach Build 2-D 2 D model ------------------------------------------ Develop Final Drawings and specifications Meet with contractor
Neutral Buoyancy No density difference exists between organic and aqueous phases. ρ DNAPL 1 g/ml DNAPL downward mobilization is reduced with creation of pools or residual blobs which are neutrally buoyant.
Neutral Buoyancy Isobutanol aqueous solution near saturation ( 10%)( is used to convert DNAPLs to LNAPLs prior to miscible displacement
Neutral Buoyancy - Objectives Phase I: Investigate effects of PCE saturation on achieving neutral buoyancy ( time = constant) Phase II: Investigate time to achieve neutral buoyancy for 14% PCE saturation (%% PCE saturation = constant)
Neutral Buoyancy Lab Methods Phase I: Key Parameters: Density (ρ)( Interfacial Tension (IFT) Viscosity (µ)( Goal: In situ density modification with minimal impact on viscosity and IFT
Neutral Buoyancy Lab Methods Phase I 1. Mix PCE and Alcohol solution 2. Separation of organic/aqueous phase 3. Measurement of Density, Viscosity, IFT
Neutral Buoyancy Initial Conditions PCE: Cl 2 C = CCl 2 PCE Fluid Properties Density IFT (with H 2 O) Dynamic Viscosity Value 1.62 g/ml 43.2 mn/m 0.90 cp
Neutral Buoyancy Preliminary Results Phase I Neutral buoyancy is reached at 0.56% PCE saturation in 24hr contact time Other methods need to be employed to improve mass transfer between alcohol solution and DNAPL when saturation is high Density DNAPL (g/ml) 1.700 1.600 1.500 1.400 1.300 1.200 1.100 1.000 Density Equilibrium - Different Saturations Before After 0 5 10 15 20 25 PCE Saturation (%)
Neutral Buoyancy Preliminary Results Phase I Dynamic Viscosity - Different Saturations 3.00 DNAPL viscosity increased when alcohol partition into DNAPL increased Viscosity DNAPL (cp) 2.50 2.00 1.50 1.00 0.50 Before After 0.00 0 5 10 15 20 25 PCE Saturation (%)
Neutral Buoyancy Preliminary Results IFT (mn/m) 50.00 40.00 30.00 20.00 10.00 IFT - Different Saturations PCE/Water Phase I Partition of alcohol solution into DNAPL reduces organic/aqueous IFT 0.00 0 5 10 15 20 PCE Saturation(%) Once IFT drops remains constant
Neutral Buoyancy Lab Methods Phase II: 14% PCE + alcohol solution Batch and Column experiments Fresh alcohol solution is injected Fresh alcohol solution is injected Aqueous Phase is removed Aqueous Phase is removed Aqueous and Organic phases are removed t =0 hr t=96hr t=192hr t=288hr
Neutral Buoyancy - Preliminary Results Phase II Density Equilibrium - 3 Flow Interruption Periods Alcohol Injec. Alcohol Injec. Alcohol Injec. Density DNAPL (g/ml) 1.600 1.500 1.400 1.300 1.200 1.100 1.000 0 50 100 150 200 250 300 Retention Time (hr) 25% density reduction was achieved
Neutral Buoyancy - Preliminary Results Viscosity - 3 Flow Interruption Periods Alcohol Inj. Alcohol Inj. Alcohol Inj. Phase II 2.00 Dynamic Viscosity (cp) 1.80 1.60 1.40 1.20 1.00 0.80 0.60 0.40 0.20 0.00 0 50 100 150 200 250 300 Retention Time (hr) IFT (mn/m) Alcohol Inj. 45.00 40.00 35.00 30.00 25.00 20.00 15.00 IFT - 3 Flow Interruption Periods Alcohol Alcohol 10.00 5.00 0.00 0 50 100 150 200 250 300 Retention Time (hr)
Recommendations for Future Work Improve in situ strategies for increasing the proportion of alcohol that can dissolve into DNAPL. The neutral buoyancy process is affected by: - Mass transfer limitations - Partitioning and presence of H 2 O in DNAPL
Recommendations for Future Work Operate 2D model under scaled conditions Control injection rates based on well locations and media characteristics Conduct miscible displacement experiments using multistep cosolvent flooding in 2D model
Acknowledgements Louisiana Board of Regents Support Fund (RCS) Tulane School of Engineering Paul Ziehl, Ph.D. CEE Talamo Machine Shop Deborah Grimm, CIF Minghua Li
Tools for Predicting DNAPL Removal from Groundwater Using Neutrally Buoyant Co-solvent Flooding Johana Husserl Ana M. Ocampo Glen R. Boyd, Ph.D, P.E. Tulane University, New Orleans, LA.