Grey water, grey area

The global shipping industry is attempting to digest the impact of upcoming regulations on the sulphur cap and ballast water management systems. It’s now time for the industry to look to its contribution to “grey water”, according to a company specialising in wastewater management solutions.

ACO Marine has called for amendments to MEPC 227(64) which currently regulates what ships do with their black water (sewage) but has nothing to say on the matter of grey water.

Grey water – domestic waste other than sewage – is largely unregulated. Yet it can form the larger percentage of water discharged overboard by ships. On the other hand, sewage, which is arguably less environmentally harmful, is subject to very stringent regulatory control.

There is a point of view that grey water is potentially more environmentally harmful than sewage. Black water, after all, is basically organic. But grey water can contain oils, fats, detergents, chemicals and greases, not to mention plastics.

Mark Beavis, managing director of ACO Marine says: “Scientific research has shown that even supposedly clean water contains significant amounts of microplastics and nanoplastics. Much of this results from the breakdown of larger plastic items. A lot has its origin in cleaning liquids and pastes, facial scrubs, toothpaste, shampoos and similar products. This is a relatively new phenomenon, but there is a move to ban the use of plastics in such products. Several countries, including the UK, have already prohibited the manufacture of toiletries and cleaning products containing plastic particles,” says Beavis.

“However, there is no international legislation to prevent the discharge of grey water waste into the oceans. Black water is regulated, but grey water is not. Some special areas – like the Baltic – have rules dealing with all types of waste from ships, but these are market-driven, not regulatory, as such.

“While MEPC 227(64) lays down requirements to limit the discharge of oils, there are no IMO standards for the separation of grease from galley water,” he says. “To my mind this is an oversight. The industry needs performance standards to work to, so that shipboard wastewater treatment systems can be optimised for effective grease separation.

“In the current absence of any performance standards, responsible manufacturers need, as a minimum, to match or exceed the land-based standards,” says Mr Beavis. “These are covered in DIN V4040-2/99, and rated at EN1825, or better still at EN1825+. These ratings define limits for lipoid content of any discharge from the separator.”

But grease traps require opening, emptying and cleaning, often on a daily basis, a task which is often not undertaken frequently enough, if at all. “The only viable solution is to fit fully-enclosed self-cleaning grease separation technology which can be maintained by ships’ engineers in the same manner as other machinery,” adds Mr Beavis.

Any ship has the potential to produce a large amount of harmful grey water which can, legally, be discharged overboard. In the case of cruise ships, the problem is magnified many times over. It is not merely influenced by the number of persons onboard – water temperature, operational periods of galleys and laundry rooms, density of galley water, detergent content and several other factors all need to be taken into consideration when specifying a complete wastewater treatment system.

Compared with the vast quantities of grease, detergent and plastic waste deposited in the sea via rivers and other discharge sources, the contribution of ships’ waste seems small – literally a drop in the ocean. But just as shipping is about to take positive action on its relatively small carbon footprint, the industry needs to have effective, demonstrable and enforceable limitations to its discharge of waste water, grey as well as black.

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