New desalination method for irrigation

Researchers from the University of Technology, Sydney (UTS) Centre for Technology in Water and Wastewater (CTWW) have developed a new way of desalinating water for irrigation. The process, designed by Dr Hokyong Shon and his colleagues, is called fertiliser-drawn forward osmosis (FDFO).

Traditional desalination plants, built to reduce reliance on rainfall, have been criticised for pushing water prices higher and adding to greenhouse gas emissions. This is because their methods rely on large-scale heating and evaporation processes, or high-pressure water pumps that force water through filtering systems. The plants are also typically expensive to maintain because of the damage saline does to plant parts.

In the new system, chemicals withdraw saline from water via osmosis by employing soluble fertiliser on the opposite side of a membrane filter. Once converted, the water is directed straight into an irrigation system via a process called fertigation. Fertiliser serves a dual purpose as a process material and part of the end product - in fact, all products and by-products involved in the system are re-usable.

The method has the potential to use up to 80% less energy than traditional forms of desalination. And with Australia using 60% of its water supply for irrigation, Dr Shon believes the system will help reduce “the demand that irrigation places on our traditional water supplies” and conserve “precious water for domestic use in our homes”.

He also hopes his team’s research into osmotic energy - the energy available from the difference in the salt concentration between seawater and river water - can be used in other areas, for example, to drive power-generating turbines.

A pilot installation of an FDFO system has been adopted by NSW State Water through the National Centre of Excellence for Desalination Australia and is currently being used at a Newcastle coal mining site to desalinate saline groundwater.

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