Exciting possibilities for water treatment
Just take a drop of arsenic, a little nitrate and fluoride then add salt!
This might be a recipe to cure all ills or, more likely, create all ills. The reality is that these contaminants are present in many of the groundwaters used to supply remote communities in Australia, China, India and many other places deprived of frequent, fresh rainfall. Such contaminants must be removed before these waters are fit for human (or even animal or plant) consumption.
The trouble is that low cost, robust, sustainable technologies for doing just this are few and far between. Reverse osmosis membrane treatment is an option but is expensive at small scale and can be challenging to maintain in its operating condition.
Researchers from the School’s Water Research Centre, Dr Peter Kovalsky and Professor David Waite, with input from doctoral student Wangwang Tang are refining technologies based on use of electrochemistry – including capacitive deionisation (CDI) and electrodialysis reversal (EDR) - to treat such waters.
These techniques involve attracting charged ions to electrodes of opposite charge (sodium to the cathode and arsenic, nitrate, fluoride and chloride to the anode) resulting in treated water with much reduced concentrations of contaminants.
The beauty of the CDI technique in particular is that it can potentially, with a little R&D, be operated using solar energy. Even better, this energy, after being used to remove the charged contaminants from the water, could potentially be recaptured and used again. Research is continuing into refining the technology for this purpose.
These exciting possibilities have been recognised by the Australian Research Council which has provided significant Linkage funds to further optimise CDI design and operating conditions - to remove particular ions of concern and to develop approaches to energy recovery. The main outcome is intended to be a photovoltaic-powered CDI unit that is capable of stand-alone operation with optimal energy recovery and inbuilt monitoring, and control technology enabling cost-effective and sustainable operation.