Water Quality Options
A potential benefit of water banking (also called Managed Aquifer Resources) is an improvement in water quality. There are a number of water banking technologies specifically used to treat surface water in order to improve water quality (from Dillon, 2004). Disinfection by-products (trihalomethanes) can be removed as well as iron, manganese, hydrogen sulphide, nitrogen, phosphorous and microorganisms (Pyne, 2002). Water banking can even be used to lower the salinity in an aquifer. Fresh injected water mixes with the saline aquifer and is then removed so that after several cycles, the zone around the bore contains fresh stored water (Pyne, 2002).
Aquifer Storage and Recovery (ASR) and Aquifer Storage, Treatment and Recovery (ASTR)
ASR and ASTR use bores to inject water into an aquifer. In the case of ASR, the same bore or an adjacent bore is used to recover the water from the aquifer. ASTR uses an adjacent bore to draw the water through the aquifer, which increases the zone of water treatment.
Figure 1: ASR and ASTR water banking
Bank Filtration
Bank filtration makes use of the connected nature of most stream/aquifer systems. Water levels are kept high in streams that lose water to the groundwater causing an increase in aquifer recharge. The water is then withdrawn from the groundwater system from a bore located near the river system.
Bank filtered water makes up a large proportion of groundwater supplies in Europe (Tuinhof and Heederik, 2002). It provides water quality improvements compared with water taken directly from the river due to the absorptive capacity of the aquifer. The other benefit is resource security because the capacity of the system is limited only by the ability of the aquifer to process the water and not by the surface water resource, which is generally much larger.
Figure 2: Bank filtration water banking
Dune Filtration
Dune filtration is another type of water banking that is used primarily for water treatment. Pretreated water is pumped into a dune swale and then reharvested at a lower level after gravity transport through the dune. Biological and chemical processes within the dune remove residual organic material, nitrogen and pathogenic microorganisms.
Figure 3: Dune filtration water banking
Soil Aquifer Treatment
Soil aquifer treatment also makes use of the natural chemical and biological processes within soil (unsaturated zone) to "polish" treated wastewater. After conventional wastewater treatment, water is pumped into infiltration ponds and then returned via recovery wells. Soil aquifer treatment is most commonly used to remove residual organic material, nitrogen and pathogenic microorganisms (NCSWS, 2001).
Figure 4: Soil aquifer treatment water banking
Relevant Links
References
Dillon P, 2004. Engineering Technologies, in Rivers and aquifers: Towards conjunctive water management, Adelaide. Workshop report, Bureau of Rural Sciences.
NCSWS, 2001. An investigation of soil-aquifer treatment for sustainable water reuse. National Center for Sustainable Water Supply [PDF 238KB]
Pyne RDG, 2002. Water quality changes during aquifer storage recovery (ASR). In Management of Aquifer Recharge for Sustainability, p. 65-68, ed P.J. Dillon, Svets and Zeitlinger B.V., Lisse, The Netherlands, 567 pp.
Tuinhof A, Heederik JP, 2002. Management of aquifer recharge and subsurface storage: making better use of our largest reservoir. Seminar, Wageningen, 18-19 December 2002. Netherlands National Committee for the International Association of Hydrogeologists.