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 
specific flowrate. In the EGCS Guidelines, oil content is not used as discharge criteria, as is the 
case for bilge water discharges, because oil discharge monitoring systems are based on UV-light 
scattering technology, which is not sensitive enough for the oil concentrations in EGCS discharge 
water. The regulation of PAH discharges to indirectly restrict oil discharges was originally 
proposed by United Kingdom (2006) because: 
1. Ithas been demonstrated that the monitoring of PAHs provides a direct surrogate to 
the monitoring of oil content. 
The instruments available to monitor PAHs have resolutions to parts per billion (ppb) 
levels and are insensitive to interference from the varying nature of sea water. 
United Kingdom (2006) assessed other regulations restricting oil discharges (such as MARPOL 
Annex I), typical amounts of other sources of oil discharges (such as oil platforms, bilge water 
and air emissions from ships) and currently available technology for water treatment; and 
considered reasonable to set the maximum content of oil in EGCS discharge water at 1 ppm. 
Relating the oil content to PAHs leads to a recommendation to set the maximum continuous 
PAHs concentration at 15 ppb (ug/L). This is based upon a specific flowrate of 45 m?*/MWh as 
originally suggested and was also drafted for the EGCS Guidelines (BLG 12/6/Add. 1). The limit 
value of 15 ppb PAH was related to the US EPA PAH16 according to US EPA Method 610. After 
reviewing the documents submitted to IMO for the development of the EGCS Guidelines, it 
remains uncertain how the current limit of 50 ppb was selected (refer to BLG 12/17 Annex 6, 
where the recommendation of the working group in BLG 12/6/Add. 1 was modified). 
Norway and Finland (2006) suggested to set tiered limit values for total hydrocarbons and PAHs 
see Table 3) in closed waters and no restrictions in the open sea, as proposed in the study of 
Buhaug et al. (2006). At a certain point (United States, 2007) limit values of 15 ppm and 5 ppm 
for oil discharges where suggested for a ship when moving and stationary, respectively. Those 
values were suggested taking as basis the MARPOL Annex I criteria (15 ppm for bilge water). 
The proposed limit values would lead to unacceptable high emissions if considering that the 
bilge water discharges from a ship can range 0.01 - 13 m?/d (CE Delft and CHEW, 2017), while a 
medium size ship with an OL system would discharge 13000 m*/d EGCS discharge water. 
Table 3: 
Compound 
THC (ppm) 
Proposed tiered limit values for total hydrocarbons and PAHs in EGCS discharge 
water as in document MEPC 55/4/7 and typical concentrations found in EGCS 
discharge water 
Tier 7 
Tier ” 
Tier 3 
| Measured 
concentrations ? 
4.5 
0.45 
0.045 
0.10—0.39 9 
PAH (ug/L) 450 | | 5 | 0.5 — 24 
THC, total hydrocarbons {in this report comparable to oil content); PAH, polycyclic aromatic hydrocarbons. Limit values are 
based in a specific flowrate of 44 m?/MWh. 
Source: adapted from Norway and Finland (2006). 
i) As reviewed from different research works and summarized in Table A-4. The values presented correspond to the range 
of concentrations found in OL systems and are not normalized to 44 m’/MWh. 
ii) In Table A-4 given as “Oil content” and includes measurements of THC and hydrocarbon oil index (depending of the 
study) 
ill) Here, the measurements of PAHepA16 are considered. It is unclear which PAH are considered for the proposed limit 
values. 
In fact, the oil content in EGCS discharge water from OL systems is in the range 0.1 - 0.4 mg/L 
(see Table 3, THC range), far below 15 ppm. PAHera16 concentrations range 0.5 - 24 ug/L (see