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| Titel |
Geochemical processes in a calcareous sandstone aquifer during managed aquifer recharge with desalinated seawater |
| VerfasserIn |
Yonatan Ganot, Amos Russak, Hagar Siebner, Anat Bernstein, Yoram Katz, Joseph Guttman, Daniel Kurtzman |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250138577
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| Publikation (Nr.) |
 EGU/EGU2017-1633.pdf |
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| Zusammenfassung |
| In the last three years we monitor Managed Aquifer Recharge (MAR) of post-treated
desalinated seawater (PTDES) in an infiltration pond, at the Menashe site that overlies the
northern part of the Israeli Coastal Aquifer. The PTDES are stabilized with CaCO3 during
post-treatment in the desalination plant and their chemical composition differs from those of
any other water recharged to the aquifer and of the natural groundwater. We use suction cups
in the unsaturated zone, shallow observation wells within the pond and production wells that
encircles the MAR Menashe site, to study the geochemical processes during MAR with
PTDES. Ion-enrichment (remineralization) of the recharged water was observed in both
unsaturated zone and shallow observation wells samples. Enrichment occurs mainly
in the first few meters below the pond surface by ion-exchange processes. Mg2+
enrichment is most prominent due to its deficiency in the PTDES. It is explained by
ion-exchange with Ca2+, as the PTDES (enriched with Ca2+) infiltrates through a
calcareous-sandstone aquifer with various amount of adsorbed Mg2+ (3–27 meq/kg). Hence,
the higher concentration of Ca+2 in the PTDES together with its higher affinity to the
sediments promotes the release of Mg2+ ions to the recharged water. Water isotopes
analysis of the production wells were used to estimate residence time and mixing
with local groundwater. At the end of 2016, it was found that the percentage of
PTDES in adjacent down-gradient production wells was around 10%, while more
distant or up-gradient wells show no mixing with PTDES. The distinct isotope
contrast between the recharged desalinated seawater (δ2H=+11.2±0.2‰) and the local
groundwater (δ2H ranged from -22.7 to -16.7‰) is a promising tool to evaluate future
mixing processes at the Menshae MAR site. Using the Menashe MAR system for
remineralization could be beneficial as a primary or complementary post-treatment
technique. However, the sustainability of this process is still questionable, as the
recharged water remineralization is accompanied by mineral depletion of the pond
sediments. Study on the feasibility of this remineralization scheme is currently
ongoing using laboratory column experiments and reactive transport modelling. |
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