Zinc and Copper Behaviour During Stormwater Aquifer Storage and Recovery in Sandy Aquifers
(2003 – 2008)
Anke Steinel (nee Wendelborn)
Amidst increasing demand and diminishing water supplies, sustainable urban water management calls for recycling and reuse of reclaimed water and stormwater. One issue is storage between collection and demand. Aquifer storage and recovery (ASR) is an option, as it requires limited space and restricts evaporation. However, stormwater contains elevated levels of heavy metals, of which Zn and Cu are most mobile, along with suspended solids, organic carbon, oxygen and nutrients, which influence behaviour of injected metals and induce geochemical changes. While stormwater ASR has been practised in South Australian limestone aquifers, field data for Melbourne’s sandy aquifers is limited, thus necessitating risk assessment.
Whilst characterisation of stormwater from Melbourne catchments confirmed high concentrations of Zn and Cu, three siliceous aquifer sediments were used in batch sorption and column experiments to assess different parameters on Zn and Cu behaviour. The reactive geochemical transport model PHT3D was modified to simulate results toward developing a predictive tool, demonstrating that injected Zn is mobile and would mainly be recovered, whereas Cu adsorption is higher with limited desorption and therefore mainly accumulates. The release of metals was triggered by reduction in pH, increase in ionic strength and particle mobilisation. Metal concentrations were also increased after storage phases, while minor sediment constituents, especially organic matter, significantly reduce metal mobility.
Recommendations include pre-treating stormwater and monitoring water quality throughout the ASR cycle, with attention to back-flushed water to ensure correct disposal.
Wendelborn, A. (2008) Zinc and Copper Behaviour During Stormwater Aquifer Storage and Recovery in Sandy Aquifers. PhD Thesis. Department of Civil Engineering, Monash University, Melbourne. link to PDF
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