The Warrnambool Sewage Treatment Plant treats sewage and industry waste from Warrnambool, Allansford and Koroit.

During the treatment process, naturally occurring bacteria and micro-organisms consume the sewage in large tanks. They completely break down the original organic solids and reduce contaminants.

Treated effluent is then decanted and discharged to the ocean into an area of high wave energy, known as a mixing zone. This helps it to mix with the sea water, minimising any harm to the environment.

During the decant process we remove the remaining organic material, known as sludge, from the bottom of the treatment tanks. The sludge comprises dead micro-organisms and a small number of active micro-organisms. It also contains inert solids (e.g. sand) that have come through the sewer.

We de-water this sludge onsite using a high-speed rotating centrifuge and then transport the de-watered sludge to our specialised facilities where it’s dried and composted. This drying or aging process takes three years, satisfying EPA guidelines. It’s then known as biosolids, a product ready for beneficial reuse as soil conditioner. The material is then spread on broad-acre agriculture, pasture and cropping properties.

The plant helps to minimise ocean pollution by treating the domestic sewage and industrial waste generated by Warrnambool, Allansford and Koroit. Once treated, the effluent is discharged into the ocean according to EPA guidelines and licence conditions.

We also work with other authorities such as the Catchment Management Authority, and Warrnambool City Council to plan for, and manage, the potential environmental impacts of ongoing development in and around Warrnambool.

The upgrade project is increasing the capacity of the Warrnambool Sewage Treatment Plant to meet the future needs of housing and economic growth in the region. It will also improve the quality of treated effluent discharged into the ocean.

Our Effluent Management Strategy is planning for the long-term future – the next 50 years. There are many options to manage the treated effluent. We need to decide which options will best serve the priorities of community and stakeholder while keeping water bills affordable.

The preferred approach for the future management of treated effluent from the plant will depend on a range of factors such as the demand for recycled water and advances in technology. We expect this will be a longer-term project over the next decade.

Most of the treated effluent is currently discharged into the ocean. A very small amount is reused to wash down screens and for general cleaning, including some of the equipment on site.

We’re considering multiple long-term options to manage effluent in the future and these are not intended to be stand-alone.

They may include enhanced screening, further disinfection, enhanced nutrient removal, an extended outfall, and treatment at the original source of the trade/industrial waste.

Understanding community and stakeholder expectations during this first round of engagement (August 2024) will help us choose the best long-term options.

We'll then share further information during Stage 2 engagement later in 2024 or early 2025

Historically, there was no centralised sewerage system in Warrnambool. Residents and businesses had to make individual arrangements for the disposal of human waste and the maintenance of reasonable levels of sanitation.

Plans to sewer the city began in the early 1930s and three years later, nearly 600 homes were connected to the sewerage system and an ocean outfall had been built. There was no screening or treatment of the sewage before it was discharged to the ocean.

In 1992, the first screening plant was installed upstream of the ocean outfall to prevent coarse material and rubbish from being discharged to the ocean.

In 1996, the Warrnambool Sewage Treatment Plant was constructed and, for the first time, effluent discharged to the ocean from Warrnambool’s residential, commercial and industrial customers underwent secondary treatment.

The inlet screening plant was upgraded in 2004 and an automatic tertiary screening system was installed on the effluent channel in 2020.

The treated effluent that is now discharged to the ocean must meet the conditions of the Environment Protection Act 2017 and our Environment Protection Authority (EPA) licence requirements.

Treated effluent is discharged into a mixing zone in the ocean at the shoreline cliff, south of the Warrnambool Sewage Treatment Plant, about 350 metres east of the Shelly Beach rock pools, 400 metres east of the sandy section of Shelly Beach, and around 1.7 kilometres west of Stingray Bay.

Treated effluent is discharged into a mixing zone in the ocean at the shoreline cliff, south of the Warrnambool Sewage Treatment Plant, about 350 metres east of the Shelly Beach rock pools, 400 metres east of the sandy section of Shelly Beach, and around 1.7 kilometres west of Stingray Bay.

Due to the risk of exposure to e-coli and enterococci, we advise people not to swim, dive, fish or be in the water within 300 metres of the ocean outfall. Signs are in place along the walking trail to indicate the area where the mixing zone is located.

As mentioned, Warrnambool’s sewerage system was first constructed in the 1930s and has historically discharged to the ocean.

The industrial waste that comes from major industries has a high salt concentration and is therefore suitable for discharge to the ocean once it’s been treated. It’s not suitable for sustainable irrigation systems or for residential dual pipe schemes without the use of a desalination process.

We’ve previously commissioned investigations into possible large-scale reuse applications, and sought expressions of interest from third parties for recycled water. However, these processes did not identify any feasible applications at the time.

Other than the high salt content, some of the other barriers to the commercial use of recycled water from the sewage treatment plant include:

• Alternative groundwater sources are plentiful and readily available for irrigation on public parks and in agriculture.
• The cost to produce recycled water at the plant would be much higher than the cost of water produced from other sources.
• There is no regulatory requirement to install dual pipe systems for non-drinking purposes such as toilet flushing, garden watering and car washing in new housing developments.
• Recycled water as a drinking water supply is not permitted in Victoria.

Our prices are not set to simply recover the operational and capital spend in any one year. They factor in a significant capital program and are calculated so that each customer pays their fair share. We recognise that customers today should not pay entirely for an asset that will last for 80 years, rather it will be paid for over time.

The way we set prices is heavily scrutinised and reviewed by our independent regulator, the Essential Services Commission.

We deliberately keep our water and sewerage service bills as stable as possible to avoid any shocks to customers. Our operational expenditure is generally quite stable and predictable, however our capital program can vary greatly from year to year.

We borrow money to fund any gaps between the money we receive and the money we pay. If the money we receive is more than we pay in a particular year, we’ll use the extra to pay down our debt.

We borrow money to fund any gaps between the money we receive and the money we pay. If the money we receive is more than we pay in a particular year, we’ll use the extra to pay down our debt.

Residential owners pay a fixed sewerage service charge to connect their property to our systems. Unlike water, there is no meter on their sewage pipe, so a residential bill is not affected by the volume that’s discharged. Tenants do not pay a sewerage charge.

Commercial and industrial customers pay a variable component for the trade waste they send us. So, the more waste that they send us, the more they pay. They’re also charged according to the quality of their waste – the poorer the quality, the more they are charged.

For some time, the bills paid by our industrial customers have risen by 2 per cent each year plus CPI. Our residential customer bills have been kept stable for some time.

The charges reflect the varying costs needed to treat the streams of waste, such as the different chemicals that are required and the electricity we use.

The sewage that flows from residential and business areas is transported through an expansive network of pipes and pump stations to reach the sewage treatment plant. These cost money to maintain and replace when necessary.

However, most commercial and industrial customers have their own specialised pre-treatment equipment and many are not as reliant on the entire sewerage network to transport waste to the plant. Industrial customers can also be required to contribute to or and pay for assets constructed specifically for them.

This information is not currently available. We'll know more as we continue our investigations and gather more information which we'll share in 2025.

Throughout this process, we’ll be seeking priorities and feedback from our community and stakeholders. This includes what is important when considering management options over the next 50 years.

The choices we make today will have various social, environmental and financial results for all Warrnambool residents and businesses over the next 50 years.

Nutrient-rich organic materials that look, smell and feel like dark, rich organic soil. Biosolids are created from the sludge which is a by-product of the sewage treatment process. We recycle 9,500 tonnes of biosolids for use as soil conditioner on farmland every year.

The liquid which is produced after sewage and industrial waste goes through the treatment process and the sludge solids are removed.

A pipe where the treated effluent is discharged into the ocean. For the Warrnambool Sewage Treatment Plant, the ocean outfall is located south of the plant, between Thunder Point and Shelly Beach.

Everything that enters the sewerage system from bathrooms, toilets, kitchens, laundries and drains. It is 99.6 per cent water. The remaining 0.4 per cent is biodegradable pollutants, plastics and small inert solid particles.

The infrastructure that collects and transfers the sewage and industrial waste to a sewage treatment plant.

Waterborne waste (other than sewage) produced by industry and businesses that is discharged through our sewerage network. Trade waste often contains substances that have to be carefully disposed of such as chemicals, grease, fats and oils. It needs to be properly managed as blockages and overflows can create serious health and safety hazards and disrupt the treatment process.

We have three types of trade waste customers:

• Business customers discharge small quantities of trade waste to our sewerage system that's a similar nature to domestic sewage. They don't require a pre-treatment device.
• Commercial customers generate trade waste that is a different strength or composition to domestic sewage. This means they need to install pre-treatment equipment (e.g. a grease trap or cooling pit) before they discharge to our network.
  
• Industrial customers generate a complex flow and/or load of trade waste. This requires a higher degree of monitoring, extra equipment, and more advanced pre-treatment before discharge.
  

Solid materials that are screened out during the treatment process and directed to landfill. They include materials such as cotton buds, dental floss, wipes, sanitary products, plastics and, grit and sand.

We direct 130 tonnes of waste products to landfill every year.

The Warrnambool Sewage Treatment Plant treats sewage and trade waste so it’s safe to discharge into the ocean mixing zone. It was commissioned in 1996 and is located between Thunder Point and Shelly Beach, about one kilometre east of Shelly Beach, and 1.7 kilometres west of Stingray Bay.