On 6 September 2026, Melbourne Water published a profile of the Western Treatment Plant (WTP) at Werribee, describing the site as a world leader in environmentally-friendly sewage treatment and outlining how a 150 megalitre per day shortcut nitrogen removal facility there is set to reshape the plant's resource-recovery role. The profile frames the WTP — roughly the size of Phillip Island — as both a working farm and an internationally recognised wetland, while tying its expansion directly to Melbourne's growth and to a net-zero-by-2030 ambition Melbourne Water.
The WTP receives about half of Melbourne's sewage and treats more than 200,000 million litres of sewage each year using a low-cost, low-energy process, with sewage flows projected to almost double by 2050 Melbourne Water. The new 5 West Nutrient Removal Plant (5W NRP), delivered with engineer Jacobs and contractor BMD, adds shortcut nitrogen removal via the nitrite shunt — one of the world's first full-scale deployments of the pathway Jacobs.
Key takeaways
- WTP at Werribee treats more than 200,000 million litres of sewage a year, about half of Melbourne's load Melbourne Water.
- Melbourne Water projects sewage flows could almost double by 2050, framing the 5W NRP as a long-horizon capacity play Melbourne Water.
- The 5W NRP is sized at 150 ML/d — about 15% of Melbourne's wastewater — and is designed to cut carbon for nitrogen removal by ~40% and energy demand by ~30% Jacobs.
- Five 85 m precast, post-tensioned bioreactor tanks are arranged in a circular "donut" around 45 m clarifiers, cutting concrete use by ~50% Jacobs.
- WTP was added to the Victorian Heritage Register in 2021 and its wetlands were listed under the Ramsar Convention in 1983 Melbourne Water.
What happened: profile and a new nutrient line
Melbourne Water's 6 September profile casts the Werribee site as a circular-economy asset, not just a sewage works: farmland irrigated with recycled water produces pasture and livestock fodder, while more than 300 bird species have been recorded across its permanent wetlands, including the critically-endangered orange-bellied parrot and the growling grass frog Melbourne Water. The site — originally the Werribee Sewage Farm, established in the early 1890s — was placed on the Victorian Heritage Register in 2021 and declared a Ramsar wetland in 1983 Melbourne Water.
The functional story is the 5W NRP. Jacobs developed the process design basis from a 2017–2020 SCNR trial at WTP, then delivered detailed design, value engineering and construction/commissioning support with contractor BMD, and is still providing operational support Jacobs. The shortcut nitrogen removal pathway stops nitrification at nitrite, converting ammonia straight to nitrogen gas and skipping the full nitrite-to-nitrate step Jacobs.
What it means for capacity, carbon and concrete
Headline performance targets reported by Jacobs: ~40% less carbon needed for nitrogen removal, ~30% lower energy demand, and ~50% less concrete than a conventional layout thanks to the donut arrangement of five 85 m bioreactors around 45 m clarifiers — gains that also lower Scope 3 emissions Jacobs. The lower carbon demand allows Melbourne Water to keep using anaerobic primary treatment and divert more carbon to biogas for on-site renewable generation, supporting its net-zero-by-2030 target flagged in the WTP profile Melbourne Water. The 5W NRP has picked up industry recognition for innovation and excellence, with image credits going to Melbourne Water Jacobs.
Specification read: buyer view of WTP and the 5W NRP
Converting the reported numbers into buyer units: 150 ML/d equals 150,000 m³/day, and on a typical per-capita wastewater basis of roughly 150–250 L/person/day (general industry range, not from the sources), the 5W NRP is the equivalent of treatment capacity for a population of roughly 600,000 to 1,000,000 people. On its own, the 5W NRP covers about 15% of Melbourne's wastewater load Jacobs, while the wider WTP already handles about half of Melbourne's sewage at more than 200,000 million litres a year, or roughly 548,000 m³/day averaged across the year Melbourne Water.
The treatment train implied by the project runs screening → primary (anaerobic, deliberately retained to feed biogas) → biological nutrient removal via SCNR/nitrite-shunt activated sludge in the donut bioreactors → secondary clarification in the 45 m clarifiers → tertiary polishing and disinfection suited to a coastal discharge at Port Phillip Bay. This event bears specifically on the biological-nutrient-removal and aeration stages, where shortcut nitrogen removal and the donut layout deliver most of the energy and concrete savings Jacobs. For a procurement engineer, the practical signal is that large-diameter precast, post-tensioned concrete tanks are now a proven option for nutrient-removal bioreactors at the 100,000+ m³/day scale, and that the integrated approach suits a plant where co-digestion of food waste is on the roadmap Melbourne Water.
If your plant runs at roughly 50,000–150,000 m³/day of mostly domestic sewage with a typical municipal BOD around 180–300 mg/L and tightening nitrogen discharge limits — the buyer profile that fits a packaged Integrated Sewage Treatment line or an Underground Package Sewage Treatment Plant (WSZ Series) for smaller sites — the WTP profile and 5W NRP results are a benchmark for what shortcut nitrogen removal can deliver on carbon, energy and concrete use, and for the kind of Municipal nutrient-removal train a heritage-constrained, space-tight site can still accommodate.
FAQ
What is shortcut nitrogen removal and why does WTP use it? It is a biological process that converts ammonia to nitrogen gas via nitrite, skipping the full nitrification step, which cuts the carbon needed for nitrogen removal by ~40% and energy demand by ~30% at the 150 ML/d 5W NRP Jacobs. Melbourne Water keeps its anaerobic primary stage so more carbon can be diverted to biogas for on-site renewable energy Melbourne Water.
How much of Melbourne's wastewater does the 5W NRP handle and at what scale? The 5W NRP is sized at 150 ML/d (150,000 m³/day), about 15% of Melbourne's wastewater, while the wider WTP takes roughly half the city's sewage at more than 200,000 million litres a year Jacobs Melbourne Water.
What are the construction and sustainability pay-offs of the donut layout? Five 85 m precast, post-tensioned bioreactor tanks are arranged in a circle around 45 m clarifiers, cutting concrete use by ~50%, lowering construction cost and reducing Scope 3 emissions, while also improving site safety during construction Jacobs. On the energy side, Jacobs reports ~30% lower treatment energy demand for the shortcut nitrogen removal stage (general industry range for similar large municipal BNR retrofits: 6–18 months for detailed design to commissioning, not from the sources).
Who delivered the 5W NRP and what is the procurement signal? Jacobs provided detailed design, value engineering, construction/commissioning support and ongoing operational support, working with Melbourne Water and contractor BMD Jacobs. For buyers, the lesson is that large nutrient-removal upgrades can be packaged as design-plus-operational-support contracts, with the supplier staying on through commissioning to bed in a novel process (general industry range, not from the sources).