Independent study calls scrubber wash water environmental impact “negligible”

The Clean Shipping Alliance (CSA) 2020 last week welcomed the preliminary results of an independent study presented by Netherlands-based research organization CE Delft, which indicated that accumulated concentrations of exhaust gas cleaning systems (EGCS, “scrubbers”) wash water components were at very low levels and well below applicable regulatory limits.

The study was presented to international delegates of the 74th session of IMO’s Marine Environment Protection Committee (MEPC) on May 14th in London.

CSA 2020 said that, along with a similar study conducted by Japan’s Transport Ministry, it was expected that the CE Delft research would help fill important gaps in the scientific record.

The CE Delft research was carried out in collaboration with Netherlands-based applied research institute Deltares, using various versions of Deltares’ computer modelling system MAMPEC. Each version represented a common configuration of European ports, and the study assumed that multiple ships in each modelled port were using open loop scrubbers 24/7/365.

The study was sponsored by CLIA Europe and Interferry. It assesses 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).

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.

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.

CSA 2020 Executive Committee Member Poul Woodall, Director, Environment & Sustainability, DFDS, said: “So far, for 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. This is an encouraging start.” CE Delft will continue to assess the accumulated concentration of scrubber discharge water compounds in two more port configurations and compare the resulting concentrations against other standards. It will also compare the compound concentrations being discharged from ships in port with the background concentrations provided to ports by other sources, such as rivers. CSA 2020 Executive Committee Member Arne Hubregtse, Executive Board Member of Spliethoff Group, observed: “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.”

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