Authorities are still dealing with contaminated water from a factory fire over two weeks ago. 

Melbourne Water is currently managing the aftermath of the Derrimut chemical fire by treating 12 million litres of contaminated firewater at its Western Treatment Plant (WTP). 

“The chemical fire may be old news, but treating the contaminated firewater will take a month,” said Kris Coventry, Head of the Western Treatment Plant.

Melbourne Water staff have been working with the state’s Environment Protection Authority (EPA) on-site at Derrimut to support the removal of this large volume of contaminated firewater runoff into a nearby sewer system connected to the WTP.

“Having chemicals like hydrocarbons - diesel, oil, gasoline - coming to a treatment plant is always a better outcome than letting them go into a waterway,” Coventry said. 

Over the next month, the contaminated water will undergo a series of aeration and decontamination processes through lagoons at the WTP. 

These lagoons contain micro-organisms designed to remove hydrocarbons from the water.

“The micro-organisms are a complex microbiota of bugs that literally ‘chew up’ the hydrocarbons in the contaminated water as part of a treatment and recycling process that is entirely natural,” Coventry said. 

The biogases emitted during this process will be captured and converted into energy to power the WTP and contribute to the electrical grid.

Post-treatment, the water will be safe for non-drinking purposes such as agriculture and industry, or it will be discharged safely into the Port Phillip bay.

Back at Derrimut, physical barriers such as sandbags, plugs, and booms remain in place at key creek locations to remove pollutants from the water. 

Absorbent booms are used to float on the creek surface, absorbing fire debris, fuels, and oils, while concrete drains are flushed, hot-washed, or pressure-washed to eliminate remaining pollution deposits.