Sewage and sewage treatment

We all make sewage, but often give little thought to where it goes, how its treated, or even, how it can be recycled.

Image shows operator Peter Skelton overlooking large treatment tanks at the Black Rock Water Reclamation Plant. Peter is wearing high-visibility safety clothing. In the background another operator is hosing down some equipment.

Another day at the 'office' for Black Rock Water Reclamation Plant operator Peter Skelton

What is sewage?

Sewage isn't just from the toilet. Waste water from your shower, bathtub, washing machine, dishwasher, kitchen sink and toilet is all considered sewage.

A typical 4-person household produces around 400–500 litres of sewage every day.

Liquid waste from business and industry is also part of the sewage stream. Industrial sewage is commonly known as trade waste.

Homes and businesses in Geelong produce around 50 million litres of sewage daily.

Sewage is 99.8% water.


Sewage or stormwater?

Stormwater is not sewage.

Stormwater is rainwater that collects on your rooftop and street, and is usually collected in gutters and underground pipes. Stormwater typically travels through creeks and rivers to the sea.

Barwon Water does not treat stormwater. In our region, stormwater is managed by local councils.


Greywater and blackwater

Waste water from your laundry and bathroom is often called greywater. Greywater can often by reused immediately, for instance on your garden.

Waste water from your toilet is sometimes called blackwater. Blackwater is not suitable for domestic reuse without a dedicated treatment system.


Sewage or sewerage?

"Sewerage" refers to the network: the sewerage system.

"Sewage" refers to the actual wastewater inside the pipes.



The sewerage system

The sewerage system consists of the pipes, pumping stations and treatment facilities that collect and treat sewage.

Our sewerage system comprises 11 water reclamation plants, over 170 sewage pumping stations, and more than 2200 kilometres of sewage pipes.


Water reclamation plants

We own and operate water reclamation plants in:

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

The Black Rock plant is the largest, and treats sewage from the greater Geelong region.

The Northern Water Plant, adjacent the Geelong Refinery in North Shore, is the newest facility.

Under contract, we also manage (but do not own) the Barwon Prison wastewater treatment plant in Lara.



Sewage treatment

Our water reclamation plants reclaim water from sewage so it can be recycled or discharged with no negative impact on the environment.

Our plants use a mix of biological, chemical and mechanical processes.



Pre-treatment involves removing objects such as paper, gravel, plastics, bottles, nappies and most identifiable solids.


Biological breakdown

Naturally-occurring bacteria and other micro-organisms use the sewage as a food source.

This process reduces the amount of suspended solids and organic material by up to 98%.

Normal by-products are water and carbon dioxide.


Nutrient removal

Phosphorus and nitrogen are typically reduced by specialised microbes that break down nitrogen compounds into nitrogen gas and absorb phosphorus in their tissues.



To further clarify the treated water it may be filtered through a sand bed or through pores in a membrane.



Disinfection destroys pathogens (disease-causing organisms) that may be present in the treated water. Our plants use chlorine or ultraviolet light.


Recycling or discharge

Treated, disinfected sewage is known as recycled water. Where possible, this recycled water is used for a range of purposes, including irrigation sporting grounds, tree lots and farms.

Excess treated water is discharged to the ocean via a submerged pipeline. (Excess water from the Colac Water Reclamation Plant is discharged to Lake Colac.)



Septic tanks

We don't manage or regulate septic tanks (it's a local council function) 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. 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.