ElectroSAnMBR

A technical overview of the ElectroSAnMBR project for ship bilge water

Ships generate a steady stream of oily wastewater below deck, known as bilge water, that accumulates in the lowest part of the hull from engine drippings, condensation, leaking pipes, lubricating oils, fuel spills, and routine wash-down activities. Across busy corridors such as the approach lanes to Sydney Harbour, the Port of Melbourne, and the shipping channels off Gladstone, this oily mixture represents one of the most persistent pollution pressures facing Australian coastal waters. When bilge water is discharged without adequate treatment, hydrocarbons, heavy metals, solvents, and high concentrations of biodegradable organic matter enter harbours and open sea, threatening fisheries, tourism, and the long-term health of ecosystems like the Great Barrier Reef.

The ElectroSAnMBR research initiative addresses this problem by merging three proven wastewater treatment concepts into a single submerged unit. Backed by the European Union Horizon 2020 programme, the project consortium is engineering a system that uses electrolysis, anaerobic digestion, and membrane filtration simultaneously to break down oily compounds, reduce chemical oxygen demand, and deliver an effluent that meets stringent discharge standards. The work carried out across multiple European laboratories is designed to produce a compact, energy-efficient reactor suited to vessels of every size, from coastal ferries servicing Sydney commuters to large commercial tankers calling at Fremantle.

The bilge water challenge for modern shipping

Bilge water rarely arrives at a treatment system as a single, well-defined contaminant. Instead, the fluid is a complex emulsion containing lubricating oils, diesel residues, hydraulic fluids, solvents used in machinery cleaning, anti-seize compounds, and traces of bilge sludge. In cold Australian waters south of Tasmania or in the tropical currents around the Torres Strait, temperature swings change the viscosity and behaviour of these oils, making separation harder for conventional oil-water separators. Marine engineers have long relied on gravity-based coalescers and absorbents, but these methods struggle with emulsified hydrocarbons, dissolved organics, and the very fine droplets that persist after mechanical treatment.

The limits of these legacy systems matter because the pollutant load in untreated bilge water is significant. Chemical oxygen demand can climb well above 10,000 mg per litre in heavily contaminated tanks, and free oil phases often exceed several thousand milligrams per litre. When such streams reach coastal receiving waters near aquaculture zones along the New South Wales south coast, they create oxygen depletion, smother benthic habitats, and introduce bioaccumulative compounds into the food chain. Australian regulators, port authorities, and vessel operators have therefore been searching for treatment technologies capable of deeper, more consistent pollutant removal than mechanical separators alone can provide.

Three technologies working in one reactor

The defining feature of the submerged anaerobic electrochemical membrane bioreactor is the way it stacks three processes into one vessel. Anaerobic digestion uses microorganisms that thrive without oxygen to convert dissolved organic matter into biogas, primarily methane and carbon dioxide. Electrolysis applies a low direct current across electrodes immersed in the same chamber, generating oxidising species and small bubbles that help break down stubborn hydrocarbons and lift fine oil droplets to the surface. A submerged membrane module then physically separates the treated water from the biomass and any remaining solids, producing a clear permeate without the need for a separate clarification tank.

The consortium is testing electrode materials that resist fouling in saline environments, membrane chemistries tailored to oily feedwaters, and biofilm communities capable of degrading aliphatic and aromatic hydrocarbons at ambient temperatures, all aligned with the project's core objectives around reactor design, energy balance, and pollutant removal efficiency. The result, in principle, is a system that handles variable loads, recovers energy from the organic fraction, and produces an effluent suitable for reuse in deck washing or even in auxiliary engine cooling loops.

Step-by-step removal of oils and chemical oxygen demand

The treatment train inside the ElectroSAnMBR begins as bilge water enters the reactor and mixes with an established consortium of anaerobic bacteria. As organic compounds are metabolised, intermediate fatty acids are produced and converted into biogas, while electrochemical reactions at the anode generate hydroxyl radicals and other oxidants that attack recalcitrant hydrocarbons. The simultaneous release of hydrogen at the cathode supports further biological activity, creating a synergistic loop that accelerates degradation. Gas bubbles produced by both biology and electrolysis help coalesce fine oil droplets, which rise to a surface layer that can be skimmed off mechanically.

Downstream of the biological and electrochemical zones, the membrane barrier retains biomass and any residual suspended solids, allowing clarified water to pass through under gentle vacuum pressure. The system targets a substantial reduction in chemical oxygen demand, often reaching removal efficiencies that would otherwise demand two or three separate reactors. Researchers are documenting these outcomes in detail, and the latest project findings show how operating parameters such as current density, hydraulic retention time, and membrane flux can be tuned to match the composition of bilge water from different vessel classes, including the mixed traffic seen at busy Australian container terminals.

Australian ports, regulations, and environmental priorities

Australia enforces strict controls on ship-sourced pollution through the Australian Maritime Safety Authority and the Protection of the Sea (Prevention of Pollution from Ships) Act 1981, which gives domestic effect to the International Convention for the Prevention of Pollution from Ships. Discharge of oil-contaminated bilge water inside designated port limits, including Port Botany, the Port of Brisbane, and Geelong, is effectively prohibited unless treated water meets tight oil-in-water thresholds. The Australian and New Zealand Guidelines for Fresh and Marine Water Quality provide a further layer of guidance for environmental protection, and port operators frequently require additional monitoring and reporting before granting discharge permissions.

These regulatory expectations are reinforced by community concern about the health of iconic marine environments. The Great Barrier Reef Marine Park Authority maintains its own zoning plan with marine park exclusion zones for vessel operations, and incidents in other Australian waters have raised public awareness of the cumulative impact of small chronic discharges. State agencies in Western Australia, South Australia, and Queensland have invested in harbour monitoring buoys and lab capacity, partly in response to the growth of offshore oil and gas logistics around Dampier and the Bass Strait. Within this environment, advanced treatment technologies attract interest from naval logistics planners, the Royal Australian Navy's environmental compliance teams, and commercial fleet owners servicing Australia's long coastline.

Research milestones and upcoming experimental phases

The ElectroSAnMBR project is organised into a series of interconnected work packages covering reactor design, membrane development, biological community characterisation, electrochemical optimisation, and pilot-scale demonstration. Early laboratory work focused on selecting electrode geometries and membrane pore sizes that can tolerate the salinity and surfactant content typical of bilge water. Current phases involve long-duration trials with synthetic and real ship-generated feedwaters, supported by analytical work tracking gas composition, fouling rates, and effluent quality. The project team includes specialists in environmental engineering, electrochemistry, membrane science, and marine microbiology, drawn from partner universities and research institutes across Europe.

Future work will move toward larger pilot reactors that can be evaluated in conditions closer to those found in harbour-side treatment facilities. Integration with onboard power systems, automated monitoring, and remote data reporting are all on the roadmap. Because the technology is being designed for modular installation, shipyards and retrofitters in Australia could eventually adapt it for harbour craft, offshore support vessels, and the support fleet that services the country's extensive network of regional ports.

Practical guidance for ports, ship operators, and regulators

Stakeholders evaluating advanced bilge water treatment options can focus their attention on a few practical priorities:

Researchers, regulators, and ship operators across Australia and the wider Indo-Pacific are invited to follow the project's progress, share operational data from their own fleets, and contribute to discussions on next-generation bilge water treatment. As pilot trials advance and demonstration units move closer to harbour-side testing, the consortium is building the partnerships needed to translate laboratory findings into working systems on real vessels, supporting cleaner harbours and stronger protection for the marine environments that Australians value so highly.