Resource 5

Melbourne's sewerage system ¹

Melbourne produces enough sewage each year to fill 140,000 Olympic-sized swimming pools; that is about 350,000 million litres! Sewage from kitchens, bathrooms, laundries and toilets ends up in the sewerage system - pipes, tunnels, pumping stations and treatment plants deal with this enormous amount of sewage.

There are about 18,100 km of sewer pipes under the streets of Melbourne. Small sewer pipes, which are about 10 cm in diameter, collect sewage from our homes. They join up to collecting sewers, which then join to the main sewers and eventually to trunk sewers. The Western Trunk Sewer, which carries sewage to the Western Treatment Plant, is 4.5 m in diameter and 22.5 km long. That's a big pipe!

The sewerage system of the greater Melbourne area
The sewerage system of the greater Melbourne area.

How does sewage get to the treatment plants?

A combination of gravity and pumping is used to take the sewage to the treatment plants. For most of the way it flows downhill like ordinary water, but Melbourne Water also has pumping stations which can pump the sewage uphill. The Brooklyn pumping station, which can pump 17,600 L of sewage a second, raises the sewage 16.5 m to the head of the trunk sewer, from where it runs downhill towards Hoppers Crossing. Another pumping station pumps the wastewater 27.5 m uphill, and from there it runs downhill to Werribee.

I live in Sunshine. Where is the sewage from my home treated?

You are part of the Western sewerage system and your wastewater is treated at the Western Treatment Plant. The treated sewage from the Western Treatment Plant empties into Port Phillip Bay.

A small amount of sewage is treated at local treatment plants owned by the three retail water companies (City West Water, South East Water and Yarra Valley Water).

Questions

  1. What is the difference between sewerage and sewage?
  2. Look in a street directory and decide which sewerage system the following suburbs are connected to: Port Melbourne, Richmond, Sandringham, Beaumaris, St Albans, Essendon, Coburg and Ascot Vale.
  3. Sewage reaches the treatment plant by a combination of gravity and pumping. Can you explain these methods?
  4. Estimate how much sewage the Brooklyn pumping station can pump in 24 hours.
  5. Workers in the sewage system sometimes talk about 'low tide'. What do they mean by this and at what time in the day or night do you think it occurs?

¹ Based on an activity from: Keith McTaggart and Paul Saddler 1993, Flushing Dunnies, Melbourne Water and Science Teachers Association of Victoria.