The monitoring and management of groundwater is a challenge. In times of water scarcity and in area with freshwater shortage, injecting or pumping water into an aquifer for storage and use at a later time, known as Aquifer Storage and Recovery, or ASR, is gaining importance. ASR can be an efficient technique to store freshwater surpluses for times of demand. During times of plentiful water, extra water can be withdrawn from a river (or other source) and then injected and stored within an aquifer. When the original water source runs low due to drought, low rainfall or other causes, this water can then be pulled from the aquifer and used.
Some ASR facilities inject treated wastewater rather than surface water into an aquifer, while other facilities inject groundwater from a different aquifer. However, the geochemical changes during the injection/retrieval as well as the hydrological changes and influences need to be assessed thoroughly. The formation of deposits and complexes can clog the systems and reduce the quality of the water. Also, in brackish-saline aquifers for instance can the density-driven flow result in limited recoverability of freshwater.
The recently developed iFLUX technology uses a modular passive flux sampler that provides simultaneous in situ point determinations of a time-averaged target compound mass flux and water flux. The sampler is typically installed in a monitoring well where it intercepts the groundwater flow and captures the compounds of interest. The sampler consists of permeable cartridges which are each packed with a specific sorbent matrix. The sorbent matrix of the water flux cartridge is impregnated with known amounts of water soluble resident tracers. These tracers are leached from the matrix at rates proportional to the groundwater flux. The measurements of the contaminants and the remaining resident tracer are used to determine groundwater and target compound fluxes.
The iFLUX sampler technology is being applied in two ASR field projects and has proven its operation and benefit. The modular design enables to determine several parameters at the same time. Currently, 6 cartridge types are validated and available: 1 groundwater flux cartridge to monitor speed and direction of flow and 5 compound cartridges to monitor different compounds – nutrients, VOC’s, metals & heavy metals, free cyanides and 1,4-dioxane. Cartridges for PFAS and pesticides are currently being developed.
The two ASR cases will be presented, together with the iFLUX technology application.