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Research Project

Assessing Pollutants in Scrubber Discharge Water from Ships

In This Report, You’ll Learn About

  • The socioeconomic and environmental concerns surrounding the use of scrubber systems on board commercial ships
  • The highlights, limitations, and conclusions of previous assessments of scrubber discharge water
  • The substances (and their concentrations) found in scrubber discharge water, how they vary by scrubber type and operations, and how they compare against current Canadian water quality guidelines
  • Key findings and recommendations related to scrubber discharge water monitoring and analysis, controlling the pollution from scrubber discharges, and effectiveness of the current International Maritime Organization (IMO) guidelines

Project Summary

In this two-step project, Clear Seas first worked with partner Serco Canada Marine to research and document the use of exhaust gas cleaning systems, commonly known as scrubbers, to reduce sulphur emissions from ships. Building on the results of this initial work, Clear Seas conducted further research to expand the literature search and source additional data for a detailed exploration of scrubber discharge water and the pollutants it contains.

This research initiative contributes new findings to the debate on the impact of scrubber discharge water, and supports effective planning, use and regulation of scrubber systems in Canadian waters and beyond. By taking an in-depth look at the data and analytical methods used across a range of studies to support diverse conclusions on scrubber impacts, this work also identifies nuances and differences between the available assessments and brings clarity to conflicting views on the acceptability of scrubbers from an environmental standpoint.

Key Takeaway

The evidence from this study supports the conclusions of policy makers and local regulatory bodies who are restricting the discharge from scrubbers in confined waters like estuaries, harbours, and anchorages. Learn more about scrubbers and why their use is contentious and restricted in some coastal areas, here.

Result Highlights

Although the discharge of low pH in scrubber water can be managed at the point of discharge or by relying on dilution in the receiving waters, the contribution of scrubber wash water to ocean acidification remains a point of concern.

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This research provides further evidence supporting the hypothesis that low pH conditions cause leaching of metal components in the scrubber system (pipes and fittings).

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While concerns about scrubbers have been focused on open-loop systems, the intermittent release of the concentrated bleed-off water from closed-loop systems are also of concern.

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Research Team

Clear Seas team member Jennifer Steele

Jennifer Steele

Director of Research Operations (on leave), Clear Seas

Clear Seas team member Paul Blomerus

Paul Blomerus

Executive Director, Clear Seas