Environmental impacts of grey water discharge from ships in the Baltic Sea

Discharge of grey water from ships is today unregulated in most sea areas, including the Baltic Sea. Annually, an estimated 5.5 million m³ grey water is emitted to the Baltic Sea with largest contribution from RoPax (4.25 million m³) and cruise ships (0.65 million m³). In total 44 different contaminants in grey water was identified and sorted into the sub categories organic compounds (28) and metals (16). Zinc and copper had the highest average concentrations with yearly inputs of 2.8 tons (zinc) and 1.5 tons (copper). 159 tons of nitrogen and 26.4 tons of phosphorus were estimated to be discharged to the Baltic Sea annually. An environmental risk assessment of contaminants, performed at a shipping lane in the Baltic Sea, showed the risk for adverse effects from grey water to be low. Nitrogen and phosphorus input from grey water contributes to 0.25% of the exceedance of, for the Baltic Sea set, eutrophication target.