Study: Accumulated Scrubber Washwater in Ports Leaves Low Environmental Impact

Ian AdamsIan Adams, Executive Director, CSA 2020. Image Courtesy: CSA 2020.

Accumulated concentrations of exhaust gas cleaning systems (EGCS) washwater components are at very low levels and well below applicable regulatory limits, the preliminary results of a new study show.

Conducted by Dutch research organization CE Delft, the study has been welcomed by the Clean Shipping Alliance (CSA) 2020.

The study, presented to international delegates of the 74th session of the International Maritime Organization’s (IMO) Marine Environment Protection Committee (MEPC) in London on May 14, will help inform the current debate regarding the environmental impact of open loop scrubbers on the marine environment, and particularly on ports and harbors, according to CSA 2020.

Along with a similar study conducted by Japan’s Transport Ministry, it is expected that the CE Delft research will help fill important gaps in the scientific record.

The research, carried out by CE Delft in collaboration with Deltares, an independent institute for applied research in the Netherlands, uses three versions of 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.

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

CE Delft researchers used washwater samples taken from the scrubber tower outlet of cruise ships, bulk carriers and ferries prior to any buffering or other washwater 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 washwater 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.

“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,” Poul Woodall, CSA 2020 Executive Committee Member and DFDS Director, Environment & Sustainability, said.

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.

“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,” Arne Hubregtse, CSA 2020 Executive Committee Member and Spliethoff Group Executive Board Member, commented.

“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,” Ian Adams, Executive Director, CSA 2020, noted.

“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 washwater.”

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

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