Ash Slurry Pump
Ash Slurry Pumps and Environmental Impacts at East Perth Power Station
Slurry pumps are widely used in industries such as mining, dredging, sand extraction, metallurgy, electric power, and coal handling. At thermal power stations like East Perth, these pumps played a critical role in managing the waste left behind from burning coal.
When coal is combusted in boilers, around 40% of it is converted into ash, though the exact composition varies depending on the type of coal, combustion process, and ash handling methods. At East Perth, this ash was collected and mixed with water by slurry pumps to form a semi-liquid waste product known as ash slurry.
This slurry was then transported under pressure through pipelines that crossed the Swan River via the Bunbury Bridge. It was deposited into lined settling ponds on the site where Optus Stadium now stands. In these ponds, the heavier solid ash particles sank to the bottom, while the water above was recycled back into the system.
Compared to dry handling methods, wet slurry pumping helped minimise airborne dust and environmental contamination. In some cases, slurry was disposed of in disused quarries. In others, fly ash was reused in construction, including during the post-WWII years when it was mixed with cement for building South Fremantle Power Station, due to material shortages.
Today, fly ash continues to be a valuable industrial by-product, especially in construction. Class C fly ash is used as a cement substitute due to its self-cementing properties and it also finds application in grouts, masonry products, roofing tiles, asphalt and even as a filler in plastic, wood products, paints, and metal castings.
However, fly ash also poses serious environmental and health risks if not properly managed. If exposed to rain, untreated ash can leach into waterways—particularly the nearby Swan River—carrying toxic elements such as arsenic, mercury, and lead.
At the time of the power station being in operation, monitoring and regulation were minimal and it’s unlikely that slurry systems or ash ponds at East Perth were adequately controlled. Workers had limited access to protective equipment, especially during maintenance and cleaning.
It wasn’t until the 1970s and 1980s that the environmental and health impacts of fly ash began to receive proper attention. Studies revealed its radioactivity, fine particle pollution and heavy metal contamination, leading to stricter oversight.
In Australia, serious monitoring of ash disposal only began in the 1980s—by which point, decades of potential contamination had already occurred. East Perth Power Station was just one of many heavy industries that left a toxic legacy in the area.
With this in mind, the 23-metre stretch of reclaimed land between the power station and the Swan River—created using fly ash—raises serious concerns. It’s not unthinkable that hazardous materials such as PCB-containing equipment were also buried in this fill, along with who knows what else!
