Sponsored by CLIA Europe and Interferry, the study is assessing the accumulated impact of exhaust gas cleaning systems on the water quality in various common port configurations by evaluating the concentration of nine metals and 16 polycyclic aromatic hydrocarbons (PAH).

Specifically, the study was presented in the MEPC 74 in London, May 14, with the aim of providing information of the current debate regarding the environmental impact of open loop scrubbers on the marine environment, and particularly on ports and harbours.

The study was conducted by CE Delft and Deltares, using three versions of up-to-date computer modelling system MAMPEC. Each of the versions used in the study present that a variety of ships use open loop scrubbers annually, all the time.

In addition, CE Delft researchers used wash water samples taken from the scrubber tower outlet of cruise ships, bulk carriers and ferries prior to any buffering or other wash water after-treatment processes.

In the first model, the researchers resulted to the fact that

For most of the compounds considered in the specified reference scenario and not considering wash water after-treatment, multiple ships using open-loop EGCSs may increase the equilibrium concentration in the port by 0% -0.01% of the annual average new Environmental Quality Standard expected to go into force in the EU in 2021, as part of a new Water Framework Directive.

Only in their assessment of concentrations of Naphthalene, Nickel, Benzo(a)pyrene, and Fluoranthene did the researchers find a slight increase in the equilibrium concentrations, though still only between 0.02% and 0.2% of the maximum annual average Environmental Quality Standard specified for 2021.

In light of these results, CSA 2020 Executive Committee Member Arne Hubregtse, Executive Board Member of Spliethoff Group, commented

These initial findings are very promising and suggest that those ships operating open-loop EGCS will have near zero impact on the quality of harbour waters.

Moreover, the researchers believe that CE Delft study will complete a similar study that was conducted by Japan’s Transport Ministry, and will fill the gaps.

CSA 2020 Executive Committee Member Poul Woodall, Director, Environment & Sustainability, DFDS, added that 'all parameters considered, the equilibrium concentrations are indicating annualised contributions on the parts per trillion scale, which we understand are actually too small to be detected by existing laboratory equipment.'

CE Delft will keep on assessing the accumulated concentration of scrubber discharge water compounds in two more port configurations and compare the resulting concentrations against other standards, while also comparing the compound concentrations being discharged from ships in port with the background concentrations provided to ports by other sources, such as rivers.

Concluding, CE Delft expects to complete and publish the study this summer.