BTO rapport - BTO 2015.025

Addressing Quality Issues During Potable Water ASR


This thesis is built upon water quality issues identified during a drinking ASR pilot project in
the Netherlands. The aquifer is considered of a representative nature for ASR standards.
Therefore, studying the issues faced and proposing solutions is considered internationally
relevant for many ASR candidate applications. The hydrogeochemical processes responsible
for the deterioration of water quality are identified and quantified in Chapter 2. The injection
of oxic source water for ASR purposes triggers oxidation reactions with the most reactive
aquifer constituents, namely pyrite, sedimentary organic material, and exchangeable Fe(II),
+, and Mn(II). The induced acidity is buffered by conversion of abundant HCO3 into CO2
and by slow dissolution of carbonate minerals such as calcite, siderite, and ankerite. As
a consequence, heavy metals such as Fe(II) and Mn(II) are released in the groundwater.
During recovery, due to inadequately high pH conditions, adsorptive removal to neoformed
ferrihydrite is not efficient and the released heavy metals reach the ASR well. Trace elements
(As, Co, Ni) released during pyrite oxidation are also observed in the groundwater at various
distances from the ASR well. The water-sediment reactions and the leaching rate of reactive
solid phases are quantified following a mass balance approach. The poor, from a drinking
perspective, quality of the abstracted water, in combination with expected post-treatment
costs, convinced the water supply company WML (Limburg, The Netherlands) to abandon
the idea of ASR application in this type of aquifer

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