The Cleveland Bay Purification Plant (CBPP) is the largest sewage treatment plant in North Queensland and vital infrastructure for the coastal town of Townsville, treating sewage from Townsville’s Southern, Eastern and Western areas.

Townsville City Council identified constraints in the plant’s ability to meet its discharge licence obligations. In 2016, it embarked on an upgrade of the plant with new flow, load, and concentration targets.

The plant is located in a Conservation Park Zone and Dugong Protection Area, and AECOM, in collaboration with Beca HunterH2O, Monadelphous, and Evoqua, delivered an upgrade that upheld industry standards and the integrity of the environmental, social, cultural, and heritage aspects of the marine park and surrounding areas. Significant design works were completed to upgrade the plant, including works across the bypass and inlet, activated sludge and bioreactor, new membrane plant, replacement of the outfall pipeline, and determining the hydraulic outfall pipeline through the plant.

Managing the risk of ageing infrastructure

A significant upgrade was needed to increase the hydraulic and treatment capacity of the plant to achieve the Department of Environment and Heritage Protection’s revised licence requirements and permit conditions.

The plant is required to fully treat sewage up to an instantaneous flow rate of 1,007 L/s (3 Average Dry Weather Flow) while meeting a range of effluent quality limits, including a median of 5 mg/L total nitrogen and 1 mg/L total phosphorus.

The team maintained the treatment plant’s compliance during treatment components shutdowns through detailed investigation and carefully integrating existing and new infrastructure. It enabled construction to be completed without breaching discharge limits. By reusing a considerable portion of the existing treatment plant structure, the project minimised construction costs and embodied carbon. The lower capital and operating cost of using existing infrastructure brought significant savings of more than $50M to the community.

A solution for the environment and community

Using a Multi-Criteria Analysis, the project team shortlisted a preferred option for upgrading and constructing the outfall pipeline. The group engaged representatives across the Great Barrier Reef Marine Park Authority, James Cook University and the Department of Environment and Heritage Protection to undertake an independent assessment.

With the community at the heart of the project, the Townsville City Council included a commitment to promote local employment in the construction contract. Using locally based suppliers and local buying behaviour practices, the project achieved ~80 percent of the Townsville region’s spending. The detailed design phase of the upgrade was predominately undertaken in Townsville, and the co-location of the AECOM and Beca HunterH2O team enabled a transfer of knowledge and skills between the organisations and local engineers.

Planning for our changing future

The upgraded CBPP delivers wastewater treatment infrastructure that is well-planned, secure, and adaptable to changes in population. The project prioritised environmental considerations and achieved a significantly higher environmental standard than the existing plant. The design can be integrated with Townsville City Council’s Effluent Reuse Strategy, with an adaptable system developed to produce high-quality recycled water that can be upgraded according to future demand. It also has the potential to be used as a water source for green hydrogen opportunities, which could reduce demand for potable water and support an industry that lessens the reliance on fossil fuels.