Melbourne Water’s one millionth-tonne of biosolids has been transported from its Eastern Treatment Plant at Bangholme, marking a major milestone in the utility’s biosolids reuse program.
Biosolids are the solid materials that are generated in the wastewater treatment process and then separated from the liquid, before being treated and dried. Melbourne Water stores significant volumes of biosolids at both the Eastern and Western wastewater treatment plants.
Treatment and Resources Manager at Melbourne Water, Jenelle Watson, said the mega-tonne milestone was a positive sign for the future of its reuse program.
“The wastewater treatment process produces many valuable resources and we need to stop seeing these as wastes, but as products that can be beneficially used,” Ms Watson said.
“For some of those resources, such as biogas, the technology is already mature and we are, for example, able to power our Western Treatment Plant from gas produced via treatment.
“However, creating a financially sustainable market for biosolids reuse has so far been more complex.”
The potential reuse opportunities of biosolids in agriculture have long been known, but over the last several years Melbourne Water has investigated other uses for biosolids, including use in the production of bricks, cement and energy.
The Eastern Treatment Plant has some biosolids with a higher percentage of clay (“clay-rich”), and specific reuse opportunities for this material including in construction, roadworks and rehabilitation earthworks have also been investigated.
Recently, strong demand emerged for Melbourne Water’s clay-rich biosolid materials to rehabilitate a collapsed landfill in outer Melbourne, meaning thousands of truckloads of material have now been taken from the Eastern Treatment Plant site.
“In recent years the opportunities to utilise the clay-rich material, particularly for geotechnical purposes, have become clearer and demand from industry has increased,” Ms Watson said.
“As a result we now expect to have completely exhausted our stockpiles of clay-rich biosolids at Eastern Treatment Plant by the end of 2019 and will need to establish new markets for ongoing production.
“Our growing population here in the greater Melbourne area means our production of this material is set to increase. We’ll be exploring all opportunities to reuse biosolids, as it is a renewable, sustainable material which has broad application across a range of industries.”