The fallout from the Derrimut chemical fire on 10 July remains ongoing, with Melbourne Water treating 12 million litres of contaminated firewater at its Western Treatment Plant (WTP) – the equivalent of six Olympic swimming pools.
Melbourne Water staff worked on-site at Derrimut with the Environment Protection Authority to support the removal of 12 million litres of contaminated firewater runoff into a nearby sewer connected to the WTP.
Melbourne Water Head of Western Treatment Plant, Kris Coventry, said, “The chemical fire may be old news, but treating the contaminated firewater will take a month.”
“Having chemicals like hydrocarbons – diesel, oil, gasoline – coming to a treatment plant is always a better outcome than letting them go into a waterway.”
Over a month, the water will go through a process of aeration and decontamination through a series of lagoons at WTP containing micro-organisms that remove hydrocarbons.
“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,” Mr Coventry said.
The biogases emitted from the process will be captured and converted to energy to power the WTP and feed the grid.
After treatment, the water will be used for non-drinking purposes (agriculture and industry) or safely discharged into the bay.
Back at Derrimut, physical barriers like sandbags, plugs, and booms remain in place at key creek locations to remove pollutants from the water.
Absorbent ‘booms’ float on the creek surface to absorb fire debris, fuels, and oils, and concrete drains are flushed, hot-washed, or pressure-washed to remove remaining pollution deposits.
Melbourne Water said responding to pollution incidents is a necessary but avoidable part of its role as a custodian of Melbourne’s waterways and catchments.
Melbourne Water has responded to 113 waterway pollution events since 1 July 2023, including 13 fires in factories or commercial premises.
Featured image: Contaminated runoff will be treated at the Western Treatment Plant’s lagoons to remove hydrocarbons. Image: Melbourne Water.
