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 
Table 3) and PAHyne values from the on-line monitoring systems recorded during the sampling 
campaign by Schmolke et al. (2020) were all below the limit value 50 ug PAHypne/L. For instance, 
air emission measurements (Fridell and Salo, 2014; Winnes et al., 2018) from ships burning 
residual fuel oil showed PAHzgpa16 emission factors upstream the EGCS in the range 1.4 - 1.7 
g/MWh. If all the PAHs would end up in the EGCS discharge water and assuming 45 m?/MWh as 
specific flowrate, the concentration of PAHgra16 in the discharge water would be in the range 31 
- 38 Hg/L. This cannot be the case, since the scrubbing removal efficiency of PAH is around 50%, 
as shown by the air emission measurements downstream the EGCS (0.77 g PAHzra16/MWh) by 
Winnes et al. (2018). In the case of CL systems, the limits could be reached even without using 
the bleed-off treatment unit (Lahtinen, 2016). Thus, the current set limit value for PAHs does not 
represent any challenge for current EGCS, so that treatment of EGCS discharge water may not be 
required for compliance. 
[t is important to establish limit values to protect the receiving waters from the high amounts of 
PAHs and oil residues discharged. Linders et al. (2019) made a simple calculation for a worst- 
case scenario assuming all ships EGCS-fitted and determined that the total emissions of PAHs 
(59 Mt) would be 10 times higher than the worldwide PAHs emissions from all sources. 
Furthermore, a deficiency of the current “2015 EGCS Guidelines” is the missing definition for 
ohenanthrene equivalents. Actually, this is a term or measuring unit established and used only 
for these Guidelines. In the review of the documentation submitted to the relevant IMO 
Committees, no document was found justifying the use of phenanthrene as surrogate parameter. 
Nevertheless, it is known that phenanthrene was chosen as surrogate parameter for PAH due to 
its high concentration in discharge water, its high solubility and its lower volatility compared to 
naphthalene. Other PAHs are insoluble or too toxic, which might pose a health risk during 
calibration of the sensors. Further information regarding the use of phenanthrene equivalents as 
a unit for the measurement of PAHs is presented by EGCSA (2012). However, the relation of 
phenanthrene equivalents to PAHzpa16 OF oil content remains unclear (US EPA, 2011). One 
manufacturer of a PAHyne Online sensor requires the application of a factor of 6.2 to account for 
all PAHzgra16, When calibrating the sensor with phenanthrene only (TriOS Mess- und 
Datentechnik, n.d.). The optical sensors for PAHyne are only capable to measure dissolved 
compounds; particulate phase is not measured and creates interferences, so that it is advisable 
to report PAHpne turbidity-corrected (TriOS Mess- und Datentechnik, n.d.). In practice, 
depending on manufacturer and ship operator, PAHyne is reported as the raw measurement, 
turbidity-corrected and/or with multiplication factor (e.g. 6.2 for PAHgpa16). 
The PAHyne concept creates confusion by stakeholders in the discussions as well; studies tried to 
compare PAHyne measurements to PAHgpra16 Or understood PAHpne as a parameter that considers 
the toxic equivalence factors for different compounds (Linders et al., 2019). It should be 
mentioned that the drafted revision of the EGCS Guidelines (as noted in chapter 5.1) will 
introduce a definition for the phenanthrene equivalents based on the wavelengths of excitation 
and detection employed by the optical measuring devices. Nevertheless, the reliability of the 
measurements remains a pending topic as stated in chapter 7.4 and reported by US EPA (2011) 
and Linders et al. (2019). 
6.3 Turbidity, suspended solids and heavy metals 
The current “2015 EGCS Guidelines” and the drafted review set a maximum limit value of 25 
FNU (or NTU) for turbidity for the difference between the inlet and discharge concentrations. 
The turbidity discharge criterion is intended to minimize the release of suspended particulate 
matter, including heavy metals and ash. Bosch et al. (2009) mentioned that turbidity was taken 
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