1Watercycle Research Institute

2Watercycle Research Institute

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)

3Watercycle Research Institute

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?

4Watercycle Research Institute

Site description

ATES site

Drinking water Pumping station

- Coarse and heterogeneous aquifer

- High groundwater flow velocity (>25 m/year)

5Watercycle Research Institute

Field data – EindhovenAmbient groundwater quality: depth profiles

-ATES system is realized in Sterksel aquifer

-Vertical redox zonation: removal of NO3, SO4; followed by appearance of CH4

6Watercycle Research Institute

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 groundwaterCycling of redox zones (Fe, NO3, NH4) consequences in aquifer?

7Watercycle Research Institute

Initial situation:

Vertical stratified aquifer:shallow groundwater enriched in SO4

deep groundwater depleted in SO4

Mixing effect explained by a simple model simulation

8Watercycle Research Institute

End of next ATES season:

Injection in other ATES well. Bel drifted further

Initial situation:

Vertical stratified aquifer:shallow Cl/SO4 enricheddeep depleted

Start with ATES:

Extraction of shallow enriched SO4 water anddeep depleted water, mixing and reinjection

Mixing effect explained by a simple model simulation

9Watercycle Research Institute

End with season 1:

Part of injected bubble has drifted off.

Mixing effect explained by a simple model simulation

10Watercycle Research Institute

End of next ATES season:

Injection in other ATES well. Bel drifted further

Initial situation:

Vertical stratified aquifer:shallow Cl/SO4 enricheddeep depleted

Start with ATES:

Extraction of shallow enriched SO4 water anddeep 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.

Mixing effect explained by a simple model simulation

11Watercycle Research Institute

Field data: microbiological observations

3x1034354.0x103454121.3Colony count 37°C (CFU/mL)

8.4x1032.4x1031.1x1041.6x1038.1x103195 Colony count 22°C (CFU/mL)

maxμmaxμmaxμ

29172919100Sulphite reducing clostridia

294296130Enterococci

2912921180E. coli

nPosnPosnPos

ATES well W10 ATES well W9 Ambient Groundwater

Parameter

- 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)

12Watercycle Research Institute

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.

13Watercycle Research Institute

Laboratory investigations

Aim: - Detailed analyses of hydrochemical changes due to changing temperature

- Investigate more extreme temp.

14Watercycle Research Institute

Collection of soil cores

15Watercycle Research Institute

Sampling of influent water

16Watercycle Research Institute

Installation in lab

Pumps

Circulation Coolers (5 and 12°C)

Cores

Control Unit(heatinglogging ofpH,DO &EC)

17Watercycle Research Institute

Selected results lab experiments: effluent curveswith 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-calcitesolid solutions (not pure calcite!)

- Desorption of cations (K, Li, Si) and trace elements (e.g. As)

18Watercycle Research Institute

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

19Watercycle Research Institute

Questions?