Background
Grey water is defined by the International Maritime Organization (IMO) as drainage from dishwashers, galley sinks, showers, laundry, baths and washbasin drains. It is a known source of contaminants to the marine environment and has been identified as a vector for microplastics in the oceans.
Currently, MARPOL Annex IV explicitly excludes grey water from the definition of sewage. Nevertheless an amendment of MARPOL to include the handling of grey water has become imperative, as more countries have introduced local or regional restrictions prohibiting the discharge of grey water, which may lead to delays or detentions of ships.
New restrictions are frequently annouced, such as the newly adopted US Vessel Incidental Discharge Act (VIDA) that defacto will make it necessary to fit a new ship with a grey water holding tank when within 12 nautical miles from land. It is expected that VIDA will enter into force in 2026.
BIMCO encourages shipowners to introduce voluntary operational measures to reduce both the amount of grey water and the sources of contaminants in it, including microplastics.
Some existing ships do have the capacity to collect and hold grey water for discharge and/or subsequent treatment. Other existing ships lead grey water from the galley and showers into their sewage treatment systems before discharging it in the sea. However most cargo ships discharge the grey water directly via runoffs into the sea. Fragmented piping and tank systems on existing ships make it extremely difficult to collect grey water for discharge to reception facilities ashore.
New ships can manage grey water for example by the following options:
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fitting a holding tank that enables retention of grey water whilst the ship is within a certain distance from land
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fitting a holding tank enabling discharge of grey water to a port reception facility when engaged in short sea trade
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leading grey water through a combined sewage and grey water treatment system with or without biotreatment
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using a grey water evaporator system.
BIMCO is actively monitoring the discussions on the potential ban of discharging grey water in sensitive sea areas where science determines that there is a particular negative impact on the marine environment.
BIMCO’s Position Statement
- BIMCO believes that due to the increasing number of local or regional grey water discharge restrictions, new ships should be built with means to prevent pollution from grey water reflecting the number of persons on board and the ship’s trade
- BIMCO supports the development of international goal-based regulations for new ships on the handling of grey water
- BIMCO is of the view that major conversions to existing ships for the management of grey water will be impracticable due to design and hull integrity limitations
- BIMCO is of the opinion that for existing ships, regulations on minimisation of contaminants and microplastics from grey water should be introduced in a pragmatic and practical way
- BIMCO supports voluntary intiatives that can reduce pollution such as microplastics filters on washing machines and the use of minimal-toxic and phosphate-free products as well as non-harmful biodegradable products
- BIMCO encourages states to ensure that sufficient reception facilities are available in their ports before introducing grey water regulations.