TEXTE Environmental Impacts of Exhaust Gas Cleaning Systems for Reduction of SOx on Ships — Analysis of status quo 
Report compiled within the framework of the project ImpEx 
systems; except for pH, but dilution is allowed in that case so that effects on regional 
acidification are not prevented. In the case of CL systems, the turbidity limit value does 
represent a restriction; thus, water treatment prior discharge is required. Since 2008, the EGCS 
Guidelines ask for a review of the discharge criteria as soon as more data on the contents of the 
discharge water and its effects become available taking into account any advice given by 
GESAMP. Within that review, the use of PAHyne as surrogate parameter for oil content should be 
clarified and the effectiveness of the turbidity criterion to prevent discharges of heavy metals 
should be addressed. 
Finally, previous and current research activities were reviewed and summarized. Studies with 
sampling campaigns on board reported logistic challenges as well as missing and unsuitable 
sampling points. Results from chemical analyses of discharge water showed generally higher 
concentrations of pollutants in CL systems than in OL systems, despite a more efficient water 
treatment being applied. Vanadium and nickel are the metals with the highest enrichment in 
discharge water. 
Studies focused on ecotoxicological analysis indicated that CL discharge water show higher 
toxicity than OL discharge water. However, when considering the flowrates, OL discharges 
represented a higher risk to marine ecosystems. Even the water treatment prior discharging in 
CL systems showed no significant reduction of toxicity effects. Results from whole effluent 
toxicity (WET) tests indicated species-specific responses to EGCS discharge water and 
demonstrated that the single-pollutant approach alone is not sufficient for the environmental 
risk assessments of EGCS discharge water. The latter might be explained by cumulative or even 
synergistic toxicity effects and by unknown pollutants present in EGCS discharge water. 
Environmental risk assessments, based on the ratio between Predicted Environmental 
Concentration and Predicted No-Effect Concentration (PEC/PNEC approach), presented 
different and opposing conclusions. The approach and methodology applied, considerations for 
determining PEC values and selected safety factors to establish PNEC values should be taken 
into account when evaluating the conclusions. 
Other national and international research projects being carried out in parallel to the ImpEx 
project and covering the assessment of EGCS discharge water were identified and generally 
described. Possible synergies with these projects are sought. 
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