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 
States are effectively bound to consider them according to Regulation 4.3 of MARPOL Annex VI 
when approving the use of EGCS as an equivalent. 
The focus of the “2015 EGCS Guidelines” is the SOx air emissions compliance. However, 
Regulation 4.4 of MARPOL Annex VI states that “equivalent methods shall endeavour not to 
impair or damage the environment, human health, property, or resources”. Based on that and on 
the environmental concerns of the EGCS discharge water, several requirements for the release of 
EGCS discharge water were developed and described under paragraph 10 of the “2015 EGCS 
Guidelines”. These include discharge criteria, continuous monitoring, data recording and 
adequate disposal of residues (sludge) ashore. The EGCS discharge water limit values for 
relevant parameters are summarised in Table 2, 
Table 2: Discharge water quality criteria as described in section 10.1 of the “2015 EGCS 
Guidelines” (Resolution MEPC.259 (68)) 
Parameter | Discharge criteria 
IH 
PAH 
Turbidity/Suspended 
Particle Matter 
Nitrates 
Water additives and other 
substances 
> 6.5 (but ApH < 2 during maneuvering and transit is allowed) or, 
> 6.5 (measured in four meters distance from the point of discharge) 
< 50 uWg/L PAHpne (Nnormalized at 45 twater/MWh) above the inlet water 
concentration and measured after any water treatment equipment but prior 
any water dilution or other reactant dosing unit. 
< 25 FNU (or 25 NTU) above the inlet water concentration and measured 
after any water treatment equipment but prior any water dilution or other 
reactant dosing unit. 
< 60 mg/L (normalized at 45 twater/MWh) at discharge or < associated with 
12% removal of NOx from the exhaust, whichever is greater. 
Special assessment, and, if necessary, additional discharge criteria should be 
established. 
The “2015 EGCS Guidelines” were revised by the IMO PPR. During PPR 7 (February 2020) a draft 
of an updated version (“2020 EGCS Guidelines”) was finalized with a view to adoption and 
approval by MEPC 75. Due to the COVID-19 pandemic, MEPC 75 was postponed (initially 
planned for April 2020) and the agenda was shortened, so that the revised EGCS Guidelines 
could not be adopted as planned. Relevant changes, as proposed by the “2020 EGCS Guidelines”, 
for the EGCS discharge water requirements are as follows: 
> Use and definition of new term “discharge water” instead of “washwater discharge” 
> Use and definition of new term “EGCS residue” instead of “washwater residue”. 
> Definition of “Z2-hour period” used for monitoring of several parameters. 
> Definition of “phenanthrene equivalent” for measurement of PAHs. 
Nitrates discharge data is to be presented as the difference between concentrations in the 
inlet water and in the discharge water. 
> Establishment of requirements for discharge water from temporary storage. 
> Establishment of permissible deviations of the discharge water monitoring equipment. 
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