Water bubbles

New Study: Scrubber Wash Water Has Negligible Environmental Impact

A new independent CE Delft study is to fill important gaps in the scientific record of exhaust gas cleaning systems (EGCS, or “scrubbers”). Preliminary result of the study is that accumulated concentrations of scrubbers' wash water components are at very low levels and well below applicable regulatory limits. 

The study, conducted by CE Delft, a research organisation in the Netherlands specialising in environmental issues, is to help inform the current debate regarding the environmental impact of open loop scrubbers on the marine environment, and particularly on ports. A similar study is being conducted by Japan’s Transport Ministry.

Ian Adams, Executive Director, Clean Shipping Alliance (CSA) 2020, added: '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.'

Dynamic Computer Modelling System

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

Impact of Scrubbers on Water Quality

Sponsored by CLIA Europe and Interferry, the ongoing study assesses 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 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.

Environmental Quality Standard

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 to 0.01 per cent 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 per cent of the maximum annual average Environmental Quality Standard specified for 2021.

Near Zero Impact

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.'

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.'

More Port Configurations to Be Researched

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.

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

Author: Mariska

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