Abstract
Managed aquifer recharge (MAR) is the intentional recharge of water to suitable aquifers for subsequent beneficial use or to achieve environmental benefits. Well injection techniques for MAR, such as Aquifer Storage and Recovery (ASR), rely on implementing appropriate design and defining the operational parameters to minimise well clogging and maintain sustainable rates of recharge over the long term. The purpose of this study was to develop water quality targets and pre-treatment requirements for recycled water to allow sustained recharge and recovery in a medium-coarse siliceous aquifer. The recharge water is a blend of 40% Class A recycled water and 60% reverse osmosis (RO)-treated Class A recycled water. Four source waters for MAR were evaluated: (1) this blend with no further treatment, and this blend with additional treatment using: (2) a 20 µm sediment cartridge filter, (3) a 5 µm sediment cartridge filter, or (4) a 5 µm granular activated carbon (GAC) cartridge filter. All four treatment options were also further disinfected with chlorine. The four blended and treated recycled waters were used in laboratory columns packed with aquifer material under saturated conditions at constant temperature (20.7 °C) with light excluded for up to 42 days. Substantial differences in the changes in hydraulic conductivity of the columns were observed for the different treatments within 14 days of the experiment, despite low turbidity (<2 NTU) of the blend waters. After 14 days, the GAC-treated water had a 7% decline in hydraulic conductivity, which was very different from the other three blend waters, which had declines of 39–52%. Based on these results and consistent with previous studies, a target biodegradable dissolved organic carbon (BDOC) level of <0.2 mg/L was recommended to ensure a biologically stable source of water to reduce clogging during recharge.
Highlights
Water recycling and reuse is becoming increasingly common throughout the world [1,2,3]
This study considered the pre-treatment requirements to allow sustained recharge of Class
The water source intended for use in ASR is a blend of 40% Class A water with 60% reverse osmosis (RO)-treated
Summary
Water recycling and reuse is becoming increasingly common throughout the world [1,2,3]. Coupling water recycling with managed aquifer recharge (MAR) can optimise the volume of water available for reuse by storing it in the aquifer for use in periods of high demand [4], provide water quality treatment [5,6], and assist with public acceptance of recycled water [7]. The most common operational issue affecting injection rate and well lifespan in all MAR operations is aquifer clogging [10,11], which can be a result of biological, physical, and/or chemical. Management strategies for clogging include both prevention (minimisation) and remediation. Operational remediation strategies for ASR are challenging and include regular backflushing, airlift redevelopment, vacuuming, chemical treatment, scrubbing, or well-enlargement, all of which require understanding of the nature of clogging (biological, physical, chemical) [11]
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