Spatial-temporal variations of the groundwater chemistry and microbiology as resulted from the operation of groundwater heat pump system – a field heat injection test

Groundwater heat pump systems (GWHP) are a promising green technology for cooling buildings. Their use is often challenging as the operation can cause disturbances to aquifer biodiversity and groundwater chemistry. Pumping can cause draw-in of dissolved oxygen in anoxic aquifers, homogenising natural depth gradient of different chemical and microbiological compositions. The resulting reactions can subsequently lead to system failure due to clogging from microbially mediated iron precipitation. Therefore, it is important to understand how the groundwater chemistry and microbiology evolve both spatially and temporally throughout the system. Field heat injection tests (HIT) were conducted to simulate its operational processes. Hierarchical clustering and principal component analyses identified different water types (chloride- or bicarbonate-water) resulted from natural processes and anthropogenic perturbations (i.e salinity, mineral dissolution, redox process). PERMANOVA revealed that microbial community composition was primarily explained by sampling depths, followed by the test phases (i.e. during HIT, recovery). Preliminary results suggested that community assembly processes corresponded well to processes caused by the HIT; where homogeneous dispersal and homogenesous selection were dominating processes under immediate perturbations, while relative fraction of heterogeneous selection increased during recovery.  Further investigations of these results will provide insights in developing optimum operational regime to minimise environmental impact to the aquifer ecosystem.

Primary Presenter: Charis Wong, Institut national de la recherche scientifique (charis.wong@inrs.ca)

Authors:

Geneviève Bordeleau, Institut national de la recherche scientifique  (genevieve.bordeleau@inrs.ca)

Jasmin Raymond, Institut national de la recherche scientifique  (jasmin.raymond@inrs.ca)

Jérôme Comte, Institut national de la recherche scientifique  (jerome.comte@inrs.ca)