Flinders University - ATES and contaminated groundwater

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November 25, 2010
Flinders University
Adelaide (Australia)

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Flinders University - ATES and contaminated groundwater

  1. 1. EFFECTS OF AQUIFER THERMAL ENERGY STORAGE (ATES) ON MOBILE CONTAMINANTS IN A GROUNDWATER SYSTEM: A MODEL APPROACH Koen Zuurbier (KWR, VU, Deltares), Niels Hartog (Deltares), Johan Valstar (Deltares), Boris van Breukelen (VU), Vincent Post (VU) 26.11.2010, Flinders, Australia
  2. 2. 2. Background: ATES and mobile contaminants <ul><li>Aquifer Thermal Energy Storage (ATES): </li></ul><ul><li>Both heat & cold </li></ul><ul><li>Use of seasonality </li></ul><ul><li>Supply by/for buildings </li></ul><ul><li>Relatively shallow aquifers </li></ul>15 - 20 o C 6 - 8 o C
  3. 3. 2. Background: ATES and mobile contaminants <ul><li>Aquifer Thermal Energy Storage (ATES): </li></ul><ul><li>Both heat & cold </li></ul><ul><li>Use of seasonality </li></ul><ul><li>Supply by/for buildings </li></ul><ul><li>Relatively shallow aquifers </li></ul>
  4. 4. 2. Background: ATES and mobile contaminants IF Technology Doublet Summer Winter
  5. 5. 2. Background: ATES and mobile contaminants ATES ≠ Geothermal Energy! Heat & cold demand Heat demand Building = supply+user Building = user
  6. 6. 2. Background: ATES and mobile contaminants BTES (Borehole Thermal Energy Storage): Closed loop systems Horizontal Vertical
  7. 7. 2. Background: ATES and mobile contaminants <ul><li>Mobile contaminants: </li></ul><ul><li>Mainly Chlorinated Hydrocarbons (VOC) </li></ul><ul><li>Chemical laundries + </li></ul><ul><li>metal industries </li></ul><ul><li>Dense Non-Aqueous </li></ul><ul><li>Phase Liquids (DNAPLs) </li></ul>ρ DNAPL > ρ water
  8. 8. <ul><li>ATES = sustainable energy </li></ul><ul><li> application desired in Greenfields and contaminated Brownfields </li></ul>2. Background: ATES and mobile contaminants Risks? Conflict Potential benefits? (source: Sanergy.nl)
  9. 9. 2. Background: ATES and mobile contaminants <ul><li>Research Program: </li></ul><ul><li>‘ More with Subsurface Energy’ </li></ul><ul><li>Consortium Research Institutes + consultants </li></ul><ul><li>Field measurements </li></ul><ul><li>modelling Study (Deltares) </li></ul><ul><li>Result: guidelines for new policies </li></ul>
  10. 10. 2. Background: ATES and mobile contaminants Aim of my study: What effect does ATES have on existing potential contaminant plumes? (focus on PCE, source contaminant) <ul><li>Plume blending in wells + reinjection (larger volume, lower C) </li></ul><ul><li>Temperature changes (density, visc., degradation?) </li></ul><ul><li>Increased dissolution of DNAPL (more water obtaining C = max solubility of VOC) </li></ul>
  11. 11. 2. Background: ATES and mobile contaminants Aim of my study: What effect does ATES have on existing potential contaminant plumes? <ul><li>Plume blending in wells (larger volume, lower C) </li></ul><ul><li>Temperature changes (density, visc., degradation ?) </li></ul><ul><li>Increased dissolution of DNAPL (more water passing, obtaining C = max solubility of VOC) </li></ul>
  12. 12. 2. Background: ATES and mobile contaminants <ul><li>Chlorinated hydrocarbons: </li></ul><ul><li>Degradation follows common sequence </li></ul><ul><li>Removal of Cl </li></ul>Reductive dechlorination VOCl (Wiedemeier, 1999) Source Products following degradation
  13. 13. 2. Background: ATES and mobile contaminants <ul><li>Dutch Environmental Protection Act: </li></ul><ul><li>Target concentrations (S-values): almost background level </li></ul><ul><li>Intervention concentrations: >100 m 3 requires remediation </li></ul>
  14. 14. 2. Background: ATES and mobile contaminants <ul><li>0 th order: </li></ul><ul><li> Constant hydrolyses org. matter = constant degradation rate </li></ul>How to describe degradation: C i = concentration component i (kg m -3 ) t = time (s) λ 0 = degradation constant 0 e order (kg m -3 s -1 ) <ul><li>1 st order: </li></ul><ul><li> Concentration contaminant </li></ul>C i = concentration component i (kg m -3 ) t = time (s) λ 0 = degradation constant 1 e order (s -1 ) C 0 = initial concentration component i (kg m -3 ) Degradation constants ( λ 0 , λ 1 ) vary with redox-conditions and component: Limited degradation of DCE and especially vinylchloride in anoxic environments Larger aquifer volume contaminated = more mass removal!!
  15. 15. 2. Background: ATES and mobile contaminants How to describe degradation: Monod kinetics: combination of 0 th and 1 st -order Not modelled (yet) At high C At low C
  16. 16. 3. Methods: modelling tools No integral modelling code available Flow: MODFLOW Transport: MT3DMS Density/Viscosity + SEAWAT (V4) Reactions: PHT3D (V2) (PHREEQC) Plume blending: Multi-Node-Well Package (MODFLOW) (total discharge  discharge per model layer) (mixing concentrations in well) Compilation
  17. 17. 4. Case study ‘Uithof’ <ul><li>Desire for realistic configurations: ATES ‘Uithof’ </li></ul><ul><li>Discharge data </li></ul><ul><li>Geohydrology (layers + heads) </li></ul><ul><li>No contamination… </li></ul> added (in model only)
  18. 18. 4. Case study ‘Uithof’ You are here Temp injection = 8 o C / 16 o C Temp background = 10,5 o C Imbalance: net 1.2 % to K1
  19. 19. 4. Case study ‘Uithof’ You are here Temp injection = 8 o C / 16 o C Temp background = 10,5 o C Imbalance: net 1.2 % to K1 N.B.: Start installation in last week of November (week 1)
  20. 20. 4. Case study ‘Uithof’ 2.8 m 50 m 56 m 41 m Vertical Cross-section 39 m 1760 m 135 m Holocene cover Aquif. 1A Sandy clay Aquif. 1B Aquitard Aquif. 2 DNAPL Holocene cover Aquif. 1A Sandy clay Aquif. 1B Aquitard Aquif. 2
  21. 21. 4. Case study ‘Uithof’ Scenario’s Here: degradation using 0 th –order (1.1*10 -9 mol L -1 d -1 ) ? x x x All factors present S-4 Increasing mass in aquifer, large volume contaminated x x Degradation absent S-3 Initial increase in volume, followed by decrease (increased degr.+blending) x x DNAPL absent S-2 Contaminated plume in +/- original size x Reference: No DNAPL, no ATES S-1 Predicted effect DNAPL ATES Degr. Characteristics Scenario
  22. 22. 5. Results <ul><li>630 l PCE at base of aquifer 1 </li></ul><ul><li>Plume developement by lateral background flow </li></ul><ul><li>Dispersion ( λ = 1m) causing mixing + broadening of plume </li></ul>Future ATES warm bubble t = 40 yr: Initial plume Conc. requiring remediation (I)
  23. 23. 5. Results <ul><li>630 l PCE at base of aquifer 1 </li></ul><ul><li>Plume developement by lateral background flow </li></ul><ul><li>Dispersion ( λ = 1m) causing mixing + broadening of plume </li></ul>Future ATES warm bubble PCE, base of aquifer 1 t = 40 yr: Initial plume Conc. requiring remediation (I)
  24. 24. 5. Results <ul><li>Scenario 1 (no DNAPL, no ATES): </li></ul><ul><li>small decrease contaminated volume </li></ul><ul><li>small decrease mass in aquifer </li></ul><ul><li>Scenario 2 (no DNAPL, but addition of ATES) </li></ul><ul><li>initial increase contaminated volume, drop in concentrations </li></ul><ul><li>after 19 yr: small volume of contaminated groundwater left </li></ul><ul><li>quick removal of mass PCE </li></ul>
  25. 25. 5. Results <ul><li>Scenario 1 & 2: </li></ul>Mainly remaining in aquitard
  26. 26. 5. Results
  27. 27. 5. Results <ul><li>Scenario 3 (DNAPL+ATES) </li></ul><ul><li>Major spreading of PCE </li></ul><ul><li>in aquifer 1 </li></ul>S I
  28. 28. t = 19 jaar
  29. 29. 5. Results <ul><li>Scenario 3: </li></ul><ul><li>>50% of DNAPL </li></ul><ul><li>in solution in 19 yr </li></ul>
  30. 30. 5. Results
  31. 31. 5. Results <ul><li>Scenario 4 (ATES, DNAPL and Degradation) </li></ul><ul><li>Limited volume </li></ul><ul><li>contaminated </li></ul><ul><li>Degradation after </li></ul><ul><li>reinjection </li></ul>S I
  32. 32. 5. Results <ul><li>Scenario 4: </li></ul><ul><li>> again >50% of DNAPL </li></ul><ul><li>in solution in 19 yr, but </li></ul><ul><li>a smaller contaminated </li></ul><ul><li>volume </li></ul>
  33. 33. 5. Results <ul><li>Scenario 4: </li></ul><ul><li>Eventually buffering </li></ul><ul><li>of mass PCE due </li></ul><ul><li>to degradation in </li></ul><ul><li>a large aquifer </li></ul><ul><li>volume </li></ul><ul><li>Dependency λ </li></ul>
  34. 34. 6. Discussion <ul><li>Important factors: </li></ul><ul><li>DNAPL (yes/no, where?) </li></ul><ul><li>Local hydro(geo)logical system (blending) </li></ul><ul><li>How to descbribe degradation, what rates, temp. effects? </li></ul>
  35. 35. 6. Discussion <ul><li>Important factors: </li></ul><ul><li>DNAPL (yes/no, where?) </li></ul><ul><li>Local hydro(geo)logical system (blending) </li></ul><ul><li>How to descbribe degradation, what rates, temp. effects? </li></ul>
  36. 36. 6. Discussion <ul><li>Degradation 1 st order: hard to get concentration below desired S-value: </li></ul>
  37. 37. 6. Discussion <ul><li>Model optimalisation? </li></ul><ul><li>computer time </li></ul><ul><li>monod kinetics </li></ul><ul><li>temp. dependent degradation </li></ul><ul><li>mixing of redox-zones?  effects on degradation </li></ul>
  38. 38. 7. Conclusions <ul><li>Important new insights on effects of ATES! </li></ul><ul><li>Positive effects ATES dissolved plume + 0 th order (expected) </li></ul><ul><li>Negative effects ATES when DNAPL near well (unexpected/not considered) </li></ul><ul><li>Blending of plume depends on local conditions (3-D modelling required) </li></ul><ul><li>Work ≠ finished (especially considering to degradation) </li></ul>

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