Cleaning up sewage (Years 9-10)

Aerial view of sewage treatment lagoons at the Western Treatment Plant
Western Treatment Plant lagoons

This lesson plan explores the key terms and innovative processes involved in treating sewage, including the benefits of biogas, nitrogen cycle, role of Melbourne's sewerage, and dissolved oxygen and aquatic ecosystems.

Each year, Melbourne Water treats over 320,000 milllion litres of sewage at its Western and Eastern treatment plants. More than half of Melbourne’s sewage is processed further to produce recycled water. The highly-treated effluent that remains is released into Port Phillip Bay or Bass Strait.

In this lesson plan, students conduct experiments that demonstrate the need to reduce nitrogen levels of the effluent and the effects of changed dissolved oxygen levels in water. The process of osmosis is examined and students debate the feasibility of treating effluent (using reverse osmosis) to drinking water standards as a supplement to Melbourne’s domestic water supply.

Download the lesson plan

This lesson plan contains modules explicitly linked to the Victorian Curriculum. It has also been adapted into an excursion tour kit that can be used in conjunction with guided tours of Melbourne Water's Western and Eastern treatment plants, run by our Education team.

Download the full plan or individual activities below.


Activity 1: Treating Melbourne’s sewage

Students are introduced to Melbourne’s sewerage and the role of Melbourne Water’s Eastern and Western Treatment Plants. They define terms used in the sewage treatment industry, identify items and substances that are introduced to the sewerage system, create a flow chart of sewage treatment processes and calculate average daily volumes of annual sewage flow.

Duration: four period sessions

Activity 2: Sludge gas and biosolids – putting waste to work

ETP truck full of biosolids

Students investigate how materials traditionally thought of as waste products can be used to improve efficiency, lower costs and decrease the carbon footprint of sewage treatment. This activity focuses on the benefits of biogas production as a renewable energy source.

Duration: two period sessions

Activity 3: The nitrogen cycle at the sewage treatment plant

Students investigate the nitrogen cycle in the real-world context of a sewage treatment plant. They design an experimental investigation to test the effect of different nitrogen compounds on plant growth and draw conclusions about the importance of minimising nutrient levels in sewage treatment discharge into Port Phillip Bay and Bass Strait.


  • Two period sessions for research
  • One period session for design and set up of experiment 
  • Allow about one to two weeks for plants to grow and students to make measurements
  • One period session for analysis of results.

Staff at Eastern Treatment Plant

Activity 4: Dissolved oxygen and aquatic ecosystems

Students conduct an experiment to observe the effects of varying dissolved oxygen levels on the organisms present in pond water. They consider the implications for sewage treatment processes.

Duration: Two period sessions with at least 24 hours between them

Activity 5: From the sewer to the glass

Students investigate the processes necessary to treat water to a standard sufficient for human consumption, conduct an experiment to demonstrate osmosis and debate whether Melbourne should use suitably treated effluent to augment its domestic water supply.

Victorian curriculum links

  • VCSSU116: The values and needs of contemporary society can influence the focus of scientific research
    Science > Science understanding > Science as a human endeavour
  • VCSSU121: Ecosystems consist of communities of interdependent organisms and abiotic components of the environment; matter and energy flow through these systems
    Science > Science understanding > Biological sciences
  • VCSSU128: Global systems, including the carbon cycle, rely on interactions involving the atmosphere, biosphere, hydrosphere and lithosphere
    Science > Science understanding > Earth and space sciences
  • VCGGK144: Different types and distribution of environmental changes and the forms it takes in different places
    Geography > Geographical knowledge > Environmental change and management
  • VCGGK145: Environmental, economic and technological factors that influence environmental change and human responses to its management
    Geography > Geographical knowledge > Environmental change and management



WTP covered anaerobic digestion lagoons

What is sewage?

Discover more about sewage, then read the benefits of 'poo power' harnessed by the treatment process. Watch our videos on the treatment process here. 


Western Treatment Plant

Western Treatment Plant virtual tour

Learn more about this world-class facility with our new virtual tour, with stunning 360-degree views you can access anytime, anywhere. 

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