Nationaal Congres Bodemenergie Effecten Van Bodemenergie Op Grondwaterkwaliteit

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Nationaal Congres Bodemenergie Effecten Van Bodemenergie Op Grondwaterkwaliteit

Nationaal Congres Bodemenergie Effecten Van Bodemenergie Op Grondwaterkwaliteit

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  • 1.  
  • 2. Research questions and approach
    • Questions:
    • What are the risks of ATES systems on groundwater quality (chemical, microbiological and physical)?
    • Where can we allow what type of ATES systems?
    • Approach/this presentation:
    • Field: Monitoring ATES systems at 3 sites (mostly 7-17 °C)
    • Lab: column experiments (5-60 °C)
    • (Numerical modelling with Seawat,Phreeqc: next step)
  • 3. Field site – ATES system Eindhoven
    • Monitoring program 2005-2012 (Brabant Water)
    • What effects are visible at field scale?
    • What is the consequence for drinking water production?
  • 4. Site description ATES site Drinking water Pumping station
    • Coarse and heterogeneous aquifer
    • High groundwater flow velocity (>25 m/year)
  • 5. Field data – Eindhoven Ambient groundwater quality: depth profiles
    • ATES system is realized in Sterksel aquifer
    • Vertical redox zonation: removal of NO3, SO4; followed by appearance of CH4
  • 6. Field data Eindhoven: Water quality patterns in ATES wells Ambient concentration range
    • Data shows:
    • Mixing of shallow Cl and SO4 enriched (anthropogenically influenced) and deep groundwater
    Cycling of redox zones (Fe, NO3, NH4)  consequences in aquifer?
  • 7. Mixing effect explained by a simple model simulation Initial situation: Vertical stratified aquifer: shallow groundwater enriched in SO 4 deep groundwater depleted in SO 4
  • 8. Mixing effect explained by a simple model simulation Start with ATES: Extraction of shallow enriched SO 4 water and deep depleted water, mixing and reinjection End of next ATES season: Injection in other ATES well. Bel drifted further Initial situation: Vertical stratified aquifer: shallow Cl/SO4 enriched deep depleted
  • 9. Mixing effect explained by a simple model simulation End with season 1: Part of injected bubble has drifted off.
  • 10. Mixing effect explained by a simple model simulation End of next ATES season: Injection in other ATES well. Bel drifted further Initial situation: Vertical stratified aquifer: shallow Cl/SO4 enriched deep depleted Start with ATES: Extraction of shallow enriched SO4 water and deep depleted water, mixing and reinjection End with season 1: Part of injected bubble has drifted off. End of storage season: Injected bubble has away from ATES well. Start of next ATES season: Injection in other ATES well.
  • 11. Field data: microbiological observations
    • - Increased elevated colony counts at 37°C
    • Higher prevalence of SSRC may indicate a faecal contamination
    • Cause unclear: drilling?, leakage along borehole?, sampling?
    • No likely risk however for PSWF due to subsurface residence time (>>100days)
    3x10 3 435 4.0x10 3 454 12 1.3 Colony count 37°C (CFU/mL) 8.4x10 3 2.4x10 3 1.1x10 4 1.6x10 3 8.1x10 3 195 Colony count 22°C (CFU/mL) max μ max μ max μ 29 17 29 19 10 0 Sulphite reducing clostridia 29 4 29 6 13 0 Enterococci 29 1 29 2 118 0 E. coli n Pos n Pos n Pos ATES well W10 ATES well W9 Ambient Groundwater Parameter
  • 12. Conclusions from field data
    • No chemical drinking water standards are exceeded. Biological standards were exceeded, but forms no likely risk for the PSWF.
    • Observed water quality impacts by the Eindhoven ATES system are explained by mixing/homogenisation of ambient vertical quality differences.
    • General conclusion (or hypothesis): mixing waters by ATES and potential microbiological contamination increases vulnerability of nearby pumping stations.
  • 13. Laboratory investigations Aim: - Detailed analyses of hydrochemical changes due to changing temperature - Investigate more extreme temp.
  • 14. Collection of soil cores
  • 15. Sampling of influent water
  • 16. Installation in lab Pumps Circulation Coolers (5 and 12 °C) Cores Control Unit (heating logging of pH,DO &EC)
  • 17. Selected results lab experiments: effluent curves with 1 day residence time
    • Results @ 5 ° C: Carbonate minerals dissolution (HCO3)
    • Results @ 25 °C: Desorption of trace elements (As)
    • Results @ 60 ° C - precipitation of siderite-calcite solid solutions (not pure calcite!)
    • Desorption of cations (K, Li, Si) and trace elements (e.g. As)
  • 18. Conclusions from column testing
    • - Lab studies show some effects at low T: carbonate dissolution (5°C) & desorption of trace elements (25°C).
    • But most effect at 60°C: desorption of cations, precipitation of Fe-Mn carbonates and respiration of organic carbon
  • 19. Questions?