Desalination plants have been controversial, mostly because of their high energy demand and the waste water they produce. But a new desalination technology uses almost no electricity and has the potential to save huge amounts of water.
Our team at Victoria University has completed a three-month power station trial in Newport, in Melbourne’s western suburbs. Using our own performance optimised design, we proved desalination of waste water – which usually relies on electricity – could instead be powered by an industry’s own waste heat.
The membrane distillation technology uses waste heat to evaporate waste water through a fine membrane. The evaporated water condenses on the other side of the membrane as treated water – at above tap water standard – for re-use around the plant.
The trial – conducted at Ecogen Energy’s intermittent operating gas fired Newport Power Station – showed the system used 50% less electricity to desalinate water than traditional techniques. An updated design was then shown to use 95% less electricity.
The improvement in the design came about from an innovative heat coupling arrangement into the membrane module that makes it possible to desalinate more water with the same size equipment.
As energy and water become increasingly scarce, this technology is a major development. If it were scaled up to a continuously operating industry of similar size to Newport Power Station it could desalinate around 7 million litres of water per day. This is the equivalent of supplying fresh water to about 25,000 people in Melbourne.
Many factories and industrial settings produced enough waste heat for this system to operate. Currently that heat is not being harnessed.
One of the most exciting outcomes of our tests is that our system can use waste heat as low as 30°C. Conventional evaporative desalination systems use 70°C or higher.
We have seen several industrial cases where there is far more waste heat available than what is needed to treat the entire site’s waste water currently going to the sewer. There are a lot of industries that are keenly watching this technology and we are already in consultation with the mining, manufacturing and dairy industries as well as water utilities to move to larger pilot trials.
The technology is relevant to many industries as saline effluent resulting from industrial processes is a common trade waste issue businesses must manage, both internally and in negotiation with water authorities.
There is active global research on membrane distillation, but what is holding back widespread use is real site trials. This is what our project was all about: demonstrating real waste water desalination using real waste heat on an industry site for a few months. So since the technology is available, with more demonstrations, it could become more widespread within a few years.
Australia’s current desalination plants are state of the art – the most efficient and reliable technology for taking fresh water from the sea. It’s more likely that membrane distillation in the future will save us from installing more of the current desalination technology, but we first need to prove the technology at gradually increasing scales. Membrane distillation technology potentially offers a more sustainable desalination option when waste heat is readily available. This is a convenient position because industries can use large amounts of water, and have a lot of waste heat!
Membrane distillation technology is just emerging globally, so our demonstration on an industry site puts us at the forefront of its international progress.
The project was supported by the Smart Water Fund and led by Water Quality Research Australia Ltd and Victoria University’s Institute for Sustainability and Innovation, with support from City West Water, GWM Water and Integrated Elements. It was funded for $97,500 by the Smart Water Fund, Water Quality Research Australia and City West Water.
Mikel Duke is Principal Research Fellow, Institute for Sustainability and Innovation at Victoria University