Through their PhD studies at Murdoch University, Ivonne Tshuma and Vishnu Ravisankar share a common goal – to make current seawater desalination techniques more energy-efficient.

The two students, under the guidance of their supervisors, Professor Wendell Ela, Doctor Ralf Cord-Ruwisch, and Associate Dean Duncan Farrow, have been working together for the past two years, sharing their findings and comparing the results of their respective methods of desalination.

While Mr Ravisankar's work has been trying to find ways to save energy using the membrane distillation process, Ms Tshuma has been exploring reducing the energy requirements of reverse osmosis, trialling a process whereby a motorised pressure pump is not required.

Current methods of desalination employed across the globe consume extremely large quantities of electricity. This is primarily due to the high volume of pressure that must be applied to seawater in order to separate the water and salt from one another in the process of reverse osmosis.

The reverse osmosis method of desalination remains the preferred option, as it is still less costly and more energy efficient than the membrane distillation process, which requires heat to desalinate seawater in large quantities.

As such, Mr Ravisankar's work has been to explore whether there is a more energy-efficient membrane distillation approach that could be taken which would make this technology more appealing.

“The membrane distillation system of desalination is really ideal for remote communities where they have limited access to conventional electricity from a power grid, as it can be fuelled by renewable energy, such as solar and wind,” he said.

“We have built a full-scale plant for a remote community in Arizona, so we know that this technology works, so my goal has been to find ways to increase its energy efficiency.

“Through my experiments in the laboratory using a modified design of a membrane distillation setup, I can see small improvements in energy savings, but to make it more appealing to industry - further optimisations of the design and operational parameters need to be done, which I am continuing to work on.”

Meanwhile, Ms Tshuma has been looking into the process of reverse osmosis, and testing new ways to apply the required amount of pressure to the seawater without using motorised machinery, such as a piston, to achieve this.

She has recently successfully designed her own seawater desalination system in Murdoch’s School of Engineering based on an original prototype invented by Dr Ralf Cord-Ruwisch and Dr Liang Cheng (original PhD from Murdoch University, PostDoc position from NCED), which achieves the desired result by using concentrated brine and seawater passing through a membrane.

This creates 'osmotic pressure' which is later used to replace desalination pumping requirements.

“I am so confident that this technology works without the need for electricity to apply the required amount of pressure, to produce potable water from seawater,” she said.

“My next steps are to re-build the device on a larger scale so it can be taken out of the lab and then trialled in a remote location to see if it can meet the water requirements of a small household.”

Once her research is complete, Ms Tshuma is hoping to work with a company to fabricate the desalination system in commercial quantities, so it can benefit remote communities throughout the world which have limited access to water and power.