Currently there are no IMO standards for the separation of fats, oils and grease from galley water, despite the treated water having to comply with the MEPC 227(64) regulation, which does not allow the discharge of any oils.
Mark Beavis, the Managing Director of water treatment specialist ACO Marine, said: “Galley water should be free of waste sludge, fats, oils and greases before it enters the treatment process otherwise biological overloading and system blockages can occur, causing system failure and possible pollution.
“Although there are standards in place for the discharge of treated sewage and bilge water, the industry should develop treatment standards for galley water which would, in the long term, prevent oily galley water being discharged directly overboard or bypassing the treatment system altogether.”
Until performance standards are in place, Beavis said grease separator manufacturers and operators need to take the environmental initiative themselves.
“Manufacturers should as a minimum look to match, or exceed, the land-based regulations for grease separator performance covered in the DIN V4040-2/99 and rated at EN1825, or better the EN1825+, which define the limits for lipoid content of any discharge from the separator. Earlier pre-conceived notions that simple grease traps were sufficient have been proven incorrect; they do not take into account neutrally buoyant substances or more dense solids which can spill over into the discharge side of the unit.”
ACO Marine has published a White Paper to offer guidance on how to specify grease separation plant in order to optimise the wastewater treatment process. 
Beavis furthered: “Of the entire ‘hotel’ wastewater generated onboard ships (toilets, sanitary, laundry and galley), galley water is the most difficult to manage and treat effectively. Yet it is often the one most overlooked. Fats, oils and greases are the single biggest contributing factor to wastewater treatment system failure, regardless of the treatment technology used.
“Early provision in the ship design for the correct grease separation technology will ensure reliable operation, and lowest risk, to the wastewater treatment system as a whole and ensure a vessel’s legislative compliance,” he said.
ACO Marine has probably the largest share of the cruiseship market for grease separation technologies with operators including all the major brands. Its Lipator and Lipatomat grease separation systems have been installed by many of the leading passenger ferry, offshore, superyacht and naval vessel builders.
Vira Maritime