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 
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Alkyl-PAHs were also present in the discharge water in significant levels, It is known that 
alkyl-PAHs, nitro-PAHs and other derivatives are found in much higher levels and some of 
them are more toxic than the parent-PAHs and PAHzg»ra16 (Linders et al., 2019). 
Results from the on-line monitoring on board presented irregularities and discrepancies 
when compared to laboratory or in situ parallel measurements. 
Water treatment after scrubbing reach different levels of efficiency depending on the 
substances and applied technology. Particulate-associated and compounds with higher 
molecular weight were efficiently removed. The use of flocculant agents and their poor 
removal might influence the discharge water composition and toxicity negatively. 
DD 
Pollutant levels in discharge water were compared to limit values in international and local 
regulations: 
Discharge water was generally compliant with IMO requirements and other limit values 
from land-based discharge regulations. 
For some substances, concentrations exceeded the comparably stricter EQS. However, 
they do not apply to single-source discharges, since dilution, environmental fate and 
zurrent environmental concentration should also be considered. 
Directive 2010/75/EU and other regulations do not include limit values for vanadium, 
which is the metal with the highest concentration in the discharge water. 
7.4.3 Ecotoxicological effects 
Based on the results of the abovementioned studies the following general observations and 
conclusions can be stated regarding ecotoxicological effects of EGCS discharge water: 
> 
CL discharge water exhibited higher toxicity effects than OL discharge water. CL systems 
require lower water flows and the water is recirculated; thus, pollutants are present in a 
more “concentrated” form. When considering the higher water flows resulting in a higher 
mass flow of pollutants, however, OL discharges represent a higher risk to marine 
ecosystems. 
Water treatment prior discharging in CL systems showed no significant reduction of toxicity 
effects. 
The single pollutant approach alone is not adequate for the environmental risk assessment 
of EGCS discharge water. Toxicity effects were observed in equivalent concentrations far 
below the reported toxicity thresholds for substances present in EGCS discharge water. This 
issue can be explained by: 
The occurrence of pollutants or toxic compounds in the EGCS discharge water that have 
not been analysed and identified yet. 
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