The Western Treatment Plant (WTP) sustainably treats more than 182,500 million litres of sewage a year, more than half of Melbourne’s sewage.

We do this using a combination of mechanised treatment and a series of large ponds, called lagoons. The sewage treatment process is also a vital part of the circular economy – turning waste into resources and helping to reuse what might otherwise be thrown away.

One of the wastes we re-use is the solid organic material created as a result of the sewage treatment process, called biosolids. Biosolids are rich in nutrients and across Australia and around the world are used on farmland to improve soil, as well as in compost and fertiliser.

At Melbourne Water, we have an active biosolids reuse program. The reuse of biosolids is regulated to ensure strict quality is achieved and is currently being used offsite to improve the soil of agricultural farmland in western Victoria. The biosolids are applied sustainably as a soil supplement and contribute nutrients, carbon and trace elements that are often scarce in Australian soils.

In 2023, the biosolids reuse program delivered 36,655 tonnes of biosolids to 44 paddocks across six farms.

This was achieved in collaboration with LOOP Organics and its partner Mahonys Transport, who delivered this over an impressive seven week period (late February to April), with trucks travelling approximately 166,000 kilometres during this time!

Farm machinery was then used to spread and incorporate the biosolids into the soil to maximise nutrient improvement.

As we implement our biosolid reuse program in the future, we will continue to work with the Environment Protection Authority Victoria, the water industry, our customers and community.