凯发

In the vast remote areas of central and north Australia, due to the scarcity of surface water, the only reliable water resource is groundwater. The total dissolved solids (TDS) concentration of the local brackish groundwater is typically around 2,000 milligrams per litre (mg/L); thus, without treatment to remove the salt, the groundwater cannot be used as drinking water. There is a huge demand for decentralised small desalination plants across regional Australia in communities, mining, agricultural and health sectors. Most of them are membrane based RO systems which requires high technical maintenance and suffers from severe scaling and fouling. In comparison, capacitive deionisation (CDI) technology has several advantages over reverse osmosis (RO). For example, it has low voltage and minimal electrical safety requirement, low energy consumption, and the potential to be coupled with the local solar energy supply in remote areas. In addition, as it is a low-pressure process, it requires less housing, pipes and pumps, and the operational costs are less than RO. However, the actual application of CDI (i.e. small pilot trials or tests of different CDI prototypes) in saline water treatment, especially in brackish groundwater treatment, has been limited and rarely reported in the literature. In this work, a portable CDI unit was tested first time as an alternative desalination technique to the conventional RO process used at Wilora, a remote Aboriginal community in the Northern Territory, Australia. The feasibility of using CDI to desalt in such location was studied. The tested CDI unit has demonstrated sufficient salinity and hardness removal ability at the remote brackish water source of Wilora, Northern Territory, Australia. At the current CDI unit configuration and local water conditions, 7 L/min (10 kL/day) is recommended as the optimal operational parameter with an energy consumption of around 0.76 kWh/m3 treated water and the 80% total water recovery rate (see Fig. 1). No significant fouling or scaling of CDI electrodes was observed for the long-term operation, despite the high concentration of calcium, magnesium and silica at the location. In addition, the current CDI unit was also found to be an effective and reliable alternative for arsenic removal from brackish water sources. WHO arsenic guidance value compliance (<0.01 mg/L) was achieved with higher than 80% removal in all designated experiments (see Fig. 2). In general, CDI removal of arsenate ions favors higher pH and lower salinity conditions. The current portable CDI technique offers a viable alternative solution to brackish water treatment especially in remote area communities where building reverse osmosis (RO) treatment plant is not practical. The data and results shown in this work can be used as guidance for the onsite operation using the current technique.

References:

[1] W. Zhang, M. Mossad, L. Zou, A study of the long-term operation of capacitive deionisation in inland brackish water desalination, Desalination, 2013, 320, 80-85.

[2] M. Mossad, W. Zhang, L. Zou, Using capacitive deionisation for inland brackish groundwater desalination in a remote location, Desalination 308 (2013) 154-160.