Melbourne Water re-uses one megatonne of biosolids

Melbourne Water has reached a major milestone in its biosolids re-use program, with the one-millionth tonne of biosolids recently transported from its Eastern Treatment Plant at Bangholme.

Biosolids are the solid materials that are generated in the wastewater treatment process and then separated from the liquid, before being treated and dried. The potential re-use opportunities of biosolids in agriculture have long been known, but over the last several years Melbourne Water has investigated other uses — including use in production of bricks, cement and energy.

The Eastern Treatment Plant has some biosolids with a high percentage of clay, and specific re-use opportunities for this material including construction, roadworks and rehabilitation earthworks have so far 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.

Jenelle Watson, Manager of Treatment and Resources at Melbourne Water, said the megatonne milestone is a positive sign for the future of the re-use program, noting, “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.

“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.”

Although Watson admitted that it has been difficult to create a financially sustainable market for biosolids re-use, she noted that the opportunities to utilise the clay-rich material, particularly for geotechnical purposes, have become clearer in recent years, with demand from industry increasing as a result.

“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,” she said.

“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 re-use biosolids, as it is a renewable, sustainable material which has broad application across a range of industries.”