Study indicates scrubber wash water has little impact in ports

Written by Nick Blenkey
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CSA 2020 Executive Committee Member Poul Woodall, Director, Environment & Sustainability, DFDS

The Clean Shipping Alliance (CSA) 2020 says that the preliminary results of an independent study indicate that accumulated concentrations of residues from exhaust gas scrubber wash water are at very low levels and well below applicable regulatory limits.

CSA 2020 Executive Committee Member Poul Woodall, Director, Environment & Sustainability, DFDS, said: “So far, for all parameters considered, the equilibrium concentrations are indicating annualized 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.”

The study has been sponsored by CLIA Europe and Interferry is being carried out by CE Delft, a Netherlands based independent research and consultancy organization specializing in environmental issues.

The initial findings were presented to delegates at last month’s 74th session of IMO’s Marine Environment Protection Committee (MEPC in London.

The research was carried out by CE Delft in collaboration with Deltares, a Netherlands based independent institute for applied research, and used three versions of Deltares’ state-of-the-art dynamic computer modeling system MAMPEC. Each version represents a common configuration of European ports, and the study assumes that multiple ships in each modeled port are using open loop scrubbers around the clock throughout the year.

The ongoing 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).

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 found 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.

According to the study’s sponsors, 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, said: “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.”

Ian Adams, Executive Director, CSA 2020, added: “Many of the those attending MEPC74 recently will have heard these preliminary results from the CE Delft study, which appear to be building on the scientific evidence showing no environmental impact to the marine environment from ships using exhaust gas cleaning systems to meet IMO 2020 guidelines.
“While there is no debate surrounding the technology’s air emissions-busting capability, we hope that the CE Delft study, along with other recently published scientific research, will help answer remaining questions surrounding the environmental impact of scrubber wash water.”

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

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