UTS technology makes saltwater more palatable and profitable
UTS develops sustainable technology to extract valuable metal and additional drinking water from wastewater
With increasing interest globally in water desalination using seawater reverse osmosis (RO), a three year project developed by the Centre for Technology in Water and Wastewater (CTWW) in the School of Civil and Environmental Engineering is maximising recovery of drinking water and valuable minerals from desalination plants.
Investment in seawater RO increases production of drinking water for populations affected by changing physical and human geography. A major challenge for RO plants is the by-product - large volumes of concentrated waste in the form of seawater brine - left by the process.
This innovative project funded by an Australian Research Council (ARC) Discovery Project Scheme has turned this disposal problem into an opportunity to increase mineral extraction and increase volumes of drinking water!
“We have developed a solution based on membrane distillation and adsorption processes that extract both Rubidium (Rb), a valuable metal, and additional freshwater—85% of the water that otherwise would be released back into the sea as brine,” said Distinguished Professor Saravanamuth Vigneswaran, Core Member, CTWW.
Containing dissolved salt, seawater brine makes up 40-50% of water going through RO. It is conventionally diluted and returned to the sea. As RO desalination plants grow in number and capacity, so too will the projected environmental and ecological impacts. Currently there is no sustainable process to manage the significant volumes of concentrated brine produced. Other emerging technologies to remove salts cannot handle the high salinity level of seawater.
Rb is a precious metal in increasing demand industrially for production of fibre optics, inorganic chemicals, lamps, night vision devices, and semiconductors. While rare in land reserves and difficult to extract, it is present in relatively large quantities in seawater.
“We can increase the concentration of Rb in seawater brine before extracting it in a pure, solid form, using a simple chemical method and air stripping. This process can be very cost effective as, for example, 5Kg of extracted Rb daily from a plant treating 100,000 tons of seawater, has a market value of @$50K,” said Professor Vigneswaran.
The UTS process includes
- using a membrane process to increase the concentration of Rb in the brine before extraction
- developing and characterising novel adsorbents to selectively adsorb Rb
- innovative adsorbent modification and encapsulation materials.
- separation and purification of Rb from desorbed chemical solution
“We now have efficient sustainable resource recovery from a process that previously created a disposal issue, leading to improved water management to meet needs in a changing environment,” said Professor Vigneswaran.