Sewage treatment plants

Keeping our communities healthy

We own, operate and maintain 17 sewage treatment plants (STPs) across the Moreton Bay, Sunshine Coast and Noosa regions.

We treat the sewage before it is re-used or discharged to rivers or oceans, following strict licence conditions issued by the Department of Environment and Science (DES). DES also monitor the effect of discharges on water quality and aquatic life.

We also produce biosolids - the nutrient-rich material created from treating wastewater solids. Biosolids are a rich source of phosphorus and nitrogen, which can be used in agriculture, composting and land rehabilitation.

The sewage treatment process

Virtual sewage treatment plant tour

Looking for educational resources for teachers and students about the water cycle and sewage treatment? Browse through our Education program.

Sewage treatment plants (STPs) in a nutshell

Unfortunately, sewage smells. However we do our very best to minimise odour at our sewage treatment plants (STPs).

We routinely implement a number of measures to lower the impact of odour on the community. These include:

sealing the sewer
regular cleaning
addition of chemicals to prevent odours being emitted
biological and chemical treatment of odour.

Odour emissions and intensity are affected by a number of variables such as the age of the sewage, wind direction, rain and temperature.

If you have any concerns regarding our sewage treatment plants, or if you notice any damage or faults, please contact us.

Unitywater is licensed to operate its sewage treatment plants (STPs) by the Department of Environment and Science (DES). To maintain our compliance, we must operate according to the strict conditions contained in these licences.

Unitywater has an effluent monitoring program for each treatment plant, as directed by DES. Effluent is sewage that has been treated through various stages.

You can see our STP performance reports and information about our effluent quality and licence compliance below:

Sewage Treatment Plant Performance Report 2022-23 (1.4MB)

Sewage Treatment Plant Performance Report 2021-22 (PDF 1.6MB)

Sewage Treatment Plant Performance Report 2020-21 (PDF 1.1MB)

Sewage Treatment Plant Performance Report 2019-20 (PDF 2MB)

Sewage Treatment Plant Performance Report 2018-19 (PDF 1.8MB)

Sewage Treatment Plant Performance Report 2017-18 (PDF 2.2MB)

Sewage Treatment Plant Performance Report 2016-17 (PDF 3.4MB)

Sewage Treatment Plant Performance Summary 2015-16 (PDF 8.2MB)

Annual Recycled Water Performance Reports

Sewage goes through a multi-stage process of treatment at our plants. These processes clean and filter the sewage to remove:

bad bacteria
non-organic matter (plastics, wet wipes etc)
organic solid matter
sediment
pollutants.

At some sewage treatment plants, we add Magnesium Hydroxide Liquid (MHL), also known as Milk of Magnesia, to raw sewage. This is an important product that helps reduce odour and protect underground assets against corrosion.

Find out more by downloading our batching plant process diagram (PDF 1.53MB)

Take a virtual video tour of a sewage treatment plant.

We own 17 sewage treatment plants (STPs). Unitywater Sewage Treatment Plant, Murrumba Downs

They are located in the following areas:

You can view STP locations on a map of our region.

How you can help

Everything you flush down the toilet or put down a sink or drain gets treated in our sewerage network.

You can help save the environment, reduce treatment costs, defer the need for expensive upgrades to our sewer networks and keep sewerage access fees down.

Here are some tips on how you can help.

And remember: definitely do not flush wet wipes down the toilet (even if the packaging says they are flushable)!

Are you smelling mangrove odour?

There are many wetlands, swamps and rivers in Unitywater’s service region of Moreton Bay, Sunshine Coast and Noosa. Many of these wetlands and rivers are home to grey mangroves, scientifically known as Avicennia marina.

With the change of weather and seasons, mangroves can release a very pungent odour that can commonly be mistaken for sewage odour. It can often be described as a rotten-egg smell and is most common between May and November. To find out more, download our mangrove fact sheet.

Download mangrove fact sheet (PDF)