0
MBR treatment plant delivered
0
of wastewater treatment capacity per day
0
automated control system
On Norfolk Island, reliable wastewater treatment is essential to everyday life. A small population and sensitive marine environment mean any disruption can quickly impact homes, farming and the surrounding coastline, making a dependable sewage treatment system critical.
By the time this project began, the island’s existing sewage treatment plant was no longer operating consistently, increasing the risk of discharge to the Marine Park and placing growing pressure on local operators.
Against this backdrop, Premise, now part of the Amey Group, delivered optioneering — the structured assessment of treatment options — followed by concept and detailed design for a new Membrane Bioreactor (MBR) sewage treatment plant, providing a more reliable and sustainable wastewater system for the island.
At a glance
- As part of the project, Premise, now part of the Amey Group, replaced a failing Rotating Biological Contactor plant with a new Membrane Bioreactor (MBR) facility
- To maintain continuous power in a diesel-reliant network, the design integrated solar, wind and 600 kWh battery storage, achieving N+1 resilience
- To address water quality and environmental risks, the plant incorporates treatment for per- and polyfluoroalkyl substances (PFAS), often referred to as “forever chemicals”, alongside reverse osmosis and effluent reuse
- The system is supported by automated control through SCADA (Supervisory Control and Data Acquisition)
What challenges arise when operating a failing sewage treatment system on a remote island?
As the condition of the Norfolk Island plant declined, the wastewater system came under increasing pressure as demand and environmental expectations increased. There was little tolerance for disruption, and any interruption would carry immediate consequences for essential services and the surrounding marine environment.
Maintaining operations became increasingly difficult. Local teams were required to manage faults and outages with limited access to specialist support, increasing operational pressure and response times.
This was compounded by a set of practical constraints that shaped how any solution could be delivered:
- An ageing Rotating Biological Contactor plant, providing limited treatment
- A remote island location and corrosive marine environment, requiring all materials to be shipped from mainland Australia
- A site located close to the airport runway, with strict Civil Aviation Safety Authority (CASA) height constraints
- A diesel-powered electricity network, where outages risk interrupting continuous treatment
- Limited access to specialist operators, placing reliance on a small local workforce
- High PFAS concentrations in influent, requiring on-island treatment as off-island disposal was not viable
These constraints meant the solution needed to work reliably within day-to-day island operations, without dependence on constant external support.
How do you design a resilient sewage treatment plant for island conditions?
In response to the complex set of challenges, Premise developed a design focused on reliability, simplicity and long-term operability in a constrained island environment. Drawing on in-house process engineering and hydraulics expertise, a structured optioneering process was used to assess and select the most appropriate treatment approach, balancing performance, constructability and operational needs.
Constructability and value for money were key drivers, given the need to ship materials to the island. With this in mind, the design brings together advanced treatment, energy and reuse systems into a single integrated solution aligned with the island’s operational realities.
The selected Membrane Bioreactor (MBR) design provides high-quality treatment through a compact and automated system. It integrates per- and polyfluoroalkyl substances (PFAS) treatment, renewable energy generation and water reuse to address the island’s specific constraints.
To deliver this, the wider system combines multiple treatment processes and supporting infrastructure:
- Packaged inlet works and conversion of existing balance tanks
- MBR treatment processes for high-quality effluent
- Sludge handling, including drying beds, a solar dryer and an incinerator
- Reverse osmosis for advanced treatment and water reuse
- Supporting infrastructure, including blower systems, chemical dosing, control and power facilities
- Off-site clean water storage and supporting assets enabling treated water reuse for farming and non-potable applications
The design reduces reliance on imported materials, specialist intervention and continuous diesel power, while ensuring the system can be operated confidently by local teams.
Key design features include:
- Reuse and rehabilitation of existing in-ground concrete tanks, reducing construction risk and minimising materials shipped to the island
- Equipment and pipework sized to allow future expansion, including additional membrane trains
- A central service corridor with above-ground pipework to improve maintenance access and vehicle movement
- Stainless steel sludge drying beds, ensuring reliable long-term operation without reliance on locally unavailable materials
- Consolidated buildings designed to meet Civil Aviation Safety Authority (CASA) height constraints and optimise use of the site footprint
- An on-site electrolytic chlorination (OSEC) system producing sodium hypochlorite from salt, water and electricity, reducing dependence on imported chemicals
The result is a system designed for reliable operation in a remote environment, supported by resilient power, advanced treatment and automated control.
Improving environmental protection, reliability and long-term resilience
Norfolk Island now benefits from a resilient, automated wastewater treatment system that improves effluent quality, reduces energy costs and supports long-term water reuse in a remote island environment.
The highly automated layout reduces operational demands, improving reliability, minimising downtime and reducing the long-term maintenance burden on Norfolk Island Regional Council. Local teams are able to operate the system with confidence, despite the island’s remote location.
This performance is underpinned by Premise’s detailed design, which transformed an ageing sewage treatment facility into a highly automated membrane bioreactor (MBR) system, addressing the island’s constraints while meeting regulatory and operational requirements. The facility achieves compliant effluent discharge standards and satisfies Civil Aviation Safety Authority (CASA) requirements.
The upgrade also delivers wider benefits for the island. A reliable supply of treated water supports local farming and non-potable reuse, reducing pressure on limited freshwater resources. At the same time, integration of renewable energy infrastructure reduces reliance on diesel generation, lowering operating costs and improving long-term financial sustainability.
Key performance outcomes include:
- Treatment capacity secured through to 2053, supporting future demand
- Power costs reduced from 72 cents per kilowatt hour (c/kWh) to 20 cents per kilowatt hour, lowering reliance on diesel generation
- Effluent quality improved to:
- 20 milligrams per litre (mg/L) Biochemical Oxygen Demand (BOD₅), indicating low levels of organic pollution
- 30 mg/L total suspended solids, indicating effective removal of particles from the water
- 15 mg/L total nitrogen
- 8 mg/L total phosphorus, protecting the surrounding Marine Park
- Up to 450 kilolitres per day (kL/day) of treated water available for reuse across the plant and local agriculture, providing an alternative water source in a resource-constrained environment
This provides Norfolk Island with a long-term, future-ready wastewater system designed for reliable operation in remote and resource-constrained environments. Premise, now part of the Amey Group, has delivered a resilient, connected solution that secures what’s critical and supports the communities it serves.