Assessing the potential impacts of geochemical processes on recovered water quality and clogging for a Managed Aquifer Recharge target in the Darling River floodplain, NSW, Australia  

Authors / CoAuthors

Vanderzalm, J. | Barry, K. | Page, D. | Dillon, P. | Brodie, R.S. | Lawrie, K.

Abstract

The potential for geochemical reactions to cause aquifer clogging or detrimental water quality changes was assessed for a managed aquifer recharge (MAR) target in the Darling River floodplain. The assessment used ambient groundwater quality from the target Calivil Formation aquifer, as well as from the shallow unconfined aquifers; Darling River source water quality; and mineralogy and geochemistry of sonic-cored aquifer samples. PHREEQC was used to examine the impact of mixing and interaction between these end-members. There is considerable variability in the redox state within the Calivil aquifer, with groundwater pe values ranging from -6 to 8. PHREEQC simulations using the median pe value of 3 resulted in super-saturation with respect to Fe(OH)3 . Hence, injection of an oxygenated source water into anoxic zones within the target aquifer can result in iron clogging due to precipitation of any source water dissolved iron and any Fe(II) oxidation in the sediments (in pyrite or displaced from exchange sites). The amount of Fe(II) within the storage zone available to be oxidised is unknown and may be limited given that Fe(III) oxides were present in the core material. The aquifer material contains species that may be released during MAR, including aluminium, arsenic, fluoride, iron, manganese, molybdenum, nickel, selenium and uranium. Injection of source water with elevated dissolved organic carbon (DOC) could enhance metal and metalloid release through reductive dissolution of iron oxides within the storage zone. The fate of any mobilised trace species would be dictated by storage zone redox conditions. Arsenic and molybdenum are likely to be adsorbed to any iron oxide surfaces under oxic conditions. Uranium and selenium are likely to reprecipitate in anoxic zones. This provides the opportunity for natural treatment within the storage zone to control mobilised trace metal species.

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nonGeographicDataset

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73803

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• External PublicationAbstract

( Theme )

• hydrogeology

( Theme )

• groundwater

( Theme )

• mineralogy

Australian and New Zealand Standard Research Classification (ANZSRC)

• Earth Sciences

• Published_Internal

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2012-03-15T00:00:00

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Creative Commons Attribution 4.0 International Licence    

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