Characterization of accumulated precipitates during subsurface iron removal

Handle URI:
http://hdl.handle.net/10754/561683
Title:
Characterization of accumulated precipitates during subsurface iron removal
Authors:
Van Halem, Doris; De Vet, W. W. J. M.; Verberk, Jasper Q J C; Amy, Gary L.; Van Dijk, Hans C.
Abstract:
The principle of subsurface iron removal for drinking water supply is that aerated water is periodically injected into the aquifer through a tube well. On its way into the aquifer, the injected O2-rich water oxidizes adsorbed Fe 2+, creating a subsurface oxidation zone. When groundwater abstraction is resumed, the soluble Fe 2+ is adsorbed and water with reduced Fe concentrations is abstracted for multiple volumes of the injection water. In this article, Fe accumulation deposits in the aquifer near subsurface treatment wells were identified and characterized to assess the sustainability of subsurface iron removal regarding clogging of the aquifer and the potential co-accumulation of other groundwater constituents, such as As. Chemical extraction of soil samples, with Acid-Oxalate and HNO3, showed that Fe had accumulated at specific depths near subsurface iron removal wells after 12 years of operation. Whether it was due to preferred flow paths or geochemical mineralogy conditions; subsurface iron removal clearly favoured certain soil layers. The total Fe content increased between 11.5 and 390.8 mmol/kg ds in the affected soil layers, and the accumulated Fe was found to be 56-100% crystalline. These results suggest that precipitated amorphous Fe hydroxides have transformed to Fe hydroxides of higher crystallinity. These crystalline, compact Fe hydroxides have not noticeably clogged the investigated well and/or aquifer between 1996 and 2008. The subsurface iron removal wells even need less frequent rehabilitation, as drawdown increases more slowly than in normal production wells. Other groundwater constituents, such as Mn, As and Sr were found to co-accumulate with Fe. Acid extraction and ESEM-EDX showed that Ca occurred together with Fe and by X-ray Powder Diffraction it was identified as calcite. © 2010 Elsevier Ltd. All rights reserved.
KAUST Department:
Biological and Environmental Sciences and Engineering (BESE) Division
Publisher:
Elsevier BV
Journal:
Applied Geochemistry
Issue Date:
Jan-2011
DOI:
10.1016/j.apgeochem.2010.11.008
Type:
Article
ISSN:
08832927
Appears in Collections:
Articles; Biological and Environmental Sciences and Engineering (BESE) Division

Full metadata record

DC FieldValue Language
dc.contributor.authorVan Halem, Dorisen
dc.contributor.authorDe Vet, W. W. J. M.en
dc.contributor.authorVerberk, Jasper Q J Cen
dc.contributor.authorAmy, Gary L.en
dc.contributor.authorVan Dijk, Hans C.en
dc.date.accessioned2015-08-03T09:02:13Zen
dc.date.available2015-08-03T09:02:13Zen
dc.date.issued2011-01en
dc.identifier.issn08832927en
dc.identifier.doi10.1016/j.apgeochem.2010.11.008en
dc.identifier.urihttp://hdl.handle.net/10754/561683en
dc.description.abstractThe principle of subsurface iron removal for drinking water supply is that aerated water is periodically injected into the aquifer through a tube well. On its way into the aquifer, the injected O2-rich water oxidizes adsorbed Fe 2+, creating a subsurface oxidation zone. When groundwater abstraction is resumed, the soluble Fe 2+ is adsorbed and water with reduced Fe concentrations is abstracted for multiple volumes of the injection water. In this article, Fe accumulation deposits in the aquifer near subsurface treatment wells were identified and characterized to assess the sustainability of subsurface iron removal regarding clogging of the aquifer and the potential co-accumulation of other groundwater constituents, such as As. Chemical extraction of soil samples, with Acid-Oxalate and HNO3, showed that Fe had accumulated at specific depths near subsurface iron removal wells after 12 years of operation. Whether it was due to preferred flow paths or geochemical mineralogy conditions; subsurface iron removal clearly favoured certain soil layers. The total Fe content increased between 11.5 and 390.8 mmol/kg ds in the affected soil layers, and the accumulated Fe was found to be 56-100% crystalline. These results suggest that precipitated amorphous Fe hydroxides have transformed to Fe hydroxides of higher crystallinity. These crystalline, compact Fe hydroxides have not noticeably clogged the investigated well and/or aquifer between 1996 and 2008. The subsurface iron removal wells even need less frequent rehabilitation, as drawdown increases more slowly than in normal production wells. Other groundwater constituents, such as Mn, As and Sr were found to co-accumulate with Fe. Acid extraction and ESEM-EDX showed that Ca occurred together with Fe and by X-ray Powder Diffraction it was identified as calcite. © 2010 Elsevier Ltd. All rights reserved.en
dc.publisherElsevier BVen
dc.titleCharacterization of accumulated precipitates during subsurface iron removalen
dc.typeArticleen
dc.contributor.departmentBiological and Environmental Sciences and Engineering (BESE) Divisionen
dc.identifier.journalApplied Geochemistryen
dc.contributor.institutionDelft University of Technology, Faculty of Civil Engineering and Geosciences, Stevinweg 1, 2628 CN Delft, Netherlandsen
dc.contributor.institutionUNESCO-IHE, Westvest 7, 2611 AX Delft, Netherlandsen
dc.contributor.institutionOasen Drinking Water Company, P.O. Box 122, 2800 AC Gouda, Netherlandsen
kaust.authorAmy, Gary L.en
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