Sewage is the wastewater from our homes, businesses and industry. It’s 99.8% water, so it can be recycled and reused in a number of ways.

Wastewater from your shower, bathtub, washing machine, dishwasher, kitchen sink and toilet is all considered sewage.

Liquid waste from businesses and industries is also part of the sewage stream, and is known as trade waste.

In total, around 50 million litres of wastewater enters our sewerage system daily.

Sewage or sewerage?

Sewage refers to wastewater. Sewerage refers to the infrastructure (like pipes, pumps and plants) that transport and treat it.

So sewage flows through sewerage pipes. The English language is confusing, isn’t it?

Our sewerage system

Sewerage systems consist of the pipes, pumping stations and treatment facilities that collect and treat sewage.

Our system includes 11 water reclamation plants, more than 170 sewage pumping stations, and more than 2,200 kilometres of pipes.

Our water reclamation plants reclaim water from sewage, so that it can be recycled or discharged safely to the environment. We operate plants at:

  • Anglesea
  • Aireys Inlet
  • Apollo Bay
  • Bannockburn
  • Birregurra
  • Colac
  • Connewarre (Black Rock water reclamation plant)
  • Lorne
  • North Shore (Northern water plant)
  • Portarlington
  • Winchelsea

The Black Rock water reclamation plant is the largest of our facilities, and treats sewage collected from the greater Geelong region. The Northern water plant, adjacent to the Geelong Refinery in North Shore, is our newest facility. Both plants produce high quality Class A recycled water.

Sewage treatment

Our reclamation plants treat wastewater using a combination of mechanical and biological processes:

  1. Pre-treatment involves the removal of objects such as paper, gravel, plastics, bottles, nappies, and more.
  2. Naturally-occurring bacteria and other micro-organisms use sewage as a food source. The biological breakdown process reduces the amount of suspended solids and organic material by up to 98%. Normal by-products of this process include water and carbon dioxide.
  3. Nutrient removal reduces levels of phosphorus and nitrogen using specialised microbes that break down nitrogen compounds into nitrogen gas, and absorb phosphorus in their tissue.
  4. To further purify the treated water, it may undergo additional filtration through a sand bed or through pores in a membrane.
  5. Disinfection using chlorine and/or ultraviolet light destroys pathogens (disease-causing organisms) that may be present in the treated water.

Treated and disinfected sewage is known as recycled water. Where possible, this water is repurposed, for example, as irrigation for sporting grounds, tree lots and farms.  All of our facilities produce Class C recycled water, or better. Higher quality (Class A) recycled water is available for residential use through a dedicated ‘purple pipe’ network.

Excess treated water is discharged to the ocean via a submerged pipeline or, in the case of the Colac Water Reclamation Plant, into Lake Colac.


The sewage treatment process utilises billions of microscopic bacteria and other organisms to break down and digest sewage to produce recycled water.

In these nutrient-rich conditions, the microbes eat, multiply and die. This organic matter accumulates at the bottom of the treatment tanks, which are regularly drained and dried. The resulting products are known as biosolids.

Biosolids have a range of uses, most notably as a nutrient-rich fertiliser. Dried biosolids can also be used as a sustainable, greenhouse-friendly alternative fuel.

Producing biosolids

Our Black Rock Water Reclamation Plant creates almost 140 tonnes of biosolids every day. The wet biosolids travel via a raised conveyor to an adjacent drying facility.

Our other plants produce biosolids in smaller quantities, which are periodically transported to the thermal dryer at the Black Rock plant.

The thermal drying process produces small biosolid pellets, which are suitable for immediate use as fertiliser, and reduces the greenhouse gas emissions previously associated with the transport and storage of biosolids.

Septic tanks

We don’t manage or regulate septic tanks (it’s the responsibility of local councils) but we do treat septic waste. Contractors pump out septic tanks and deliver the effluent to our reclamation plants for treatment.

Septic tanks require regular maintenance. If you own a septic tank, we recommend you:

  • inspect your septic system at least once a year
  • check your sludge levels and pumps regularly
  • have your tank pumped out by an accredited contractor at least once every 3 years
  • minimise the amount of food scraps, fats and oils in your septic system
  • don’t add grease, paint, nappies or feminine hygiene products to your septic tank
  • avoid strong detergents, cleaners and bleach that can destroy the micro-organisms that break down waste products in your tank
  • ensure your septic tank and disposal field are accessible and not built over.

We may not accept poorly managed or contaminated septic waste.

For more information on septic tanks and how to manage your septic waste system, please contact your local council.

Pressure sewer systems

A pressure sewer system is a network of sealed pipes and small, below-ground pump stations at some connected properties. The pump stations collect household sewage and pump it to the sewer main, located in the street.

Pressure sewer systems are used in certain areas because of topography, the unsuitability of ground conditions and/or cost of a conventional sewerage system.

Learn more about pressure sewer systems