The unprocessed and untreated waste material generated from commercial and household activities such as washing dishes and clothes, taking a shower and flushing the toilet.

Primary treatment

Primary treatment is where liquids and solids are separated using fine screens.

Secondary treatment

Any leftover materials from the primary treatment are removed using an activated sludge process. Bacteria naturally treats the sewage using a bioreactor and settling tanks, and nutrients such as nitrogen and phosphorus are removed.

Tertiary treatment

In tertiary treatment, the sewage undergoes processing to make it safer for release into the environment.
This can include removing bacteria by filtering and disinfecting the wastewater before release.

Once the wastewater has been treated and tested to meet high quality standards, it can be used by agriculture and industries that don’t require drinking quality water with the remainder returned to our waterways.

The process of treating sewage to remove or inactivate organisms capable of infection or harm, and reducing bacteria to a safe level. Several stages of disinfection ensures the treated wastewater can enter waterways or be recycled for irrigation use. Common methods of disinfection include chlorination and ozonation.

Activated sludge is aerated sewage containing microorganisms that help to break down the organic content of waste. The mass of microorganisms, commonly referred to as biological floc, include bacteria, protozoa and a range of other filter feeding species. The activated sludge process occurs in bioreactors and helps to speed up waste decomposition, and the separation of liquids and solids.

Biosolids refers to the organic material produced during sewage treatment that is safe to be recycled for further use. Derived from the treatment of the solid components of sewage, biosolids can be used for the production of biogas, composting, landscaping or as an agricultural fertiliser. Biosolids contain nutrients key to stimulating plant growth and improving the productivity of soils. Strict state and national guidelines in Australia specify how biosolids can be used. More information about biosolids is available at

Former wastewater that is filtered, treated and disinfected to remove solids and impurities. Recycled water is safe and suitable for various purposes, including irrigating ovals, golf courses and crops.
Bioreactors are manufactured devices and systems that support a biologically active environment. In sewage treatment, bioreactors are the tanks in which the activated sludge break down sewage and separate liquid and solids occurs.