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 
as monitoring value because it is a simple method for on-line analysis; however, they remarked 
that: 
1. Turbidity is not a direct method of determining the number of exhaust particles that 
end up in the EGCS discharge water. 
There is no direct correlation between turbidity and particle concentration. 
Turbidity is strongly dependent on the particles size in the water (smaller particles are 
likely to have significantly less influence on the measured turbidity than larger ones). 
Studies are required to find a correlation between turbidity and concentrations of 
suspended solids, metals and ash in the EGCS discharge water before this criterion can 
be considered a surrogate of those pollutants. 
As highlighted in chapter 7.4, no research works were found examining the relation between 
turbidity, suspended solids, organic pollutants and metals. It is crucial to work on determining 
whether turbidity can be used as a surrogate parameter to protect receiving waters from metals 
discharges. Even though the turbidity values in the EGCS discharge water are far below the 
limits of the EGCS Guidelines, a considerable amount of metals is released that could pose a risk 
to the environment (US EPA, 2011). Further, the majority of the metals are found in the 
dissolved fraction (and not in particulate form), presumably due to the acidic conditions and 
high levels of chloride in the water (see chapter 7.4). 
This limit value does not represent any challenge for OL systems and can be complied without 
water treatment (see Table A-4). On the other hand, because the set limit value is not 
normalized, for CL systems it represents a restriction and water treatment (no dilution) prior 
discharge is required. To this regard, Lahtinen (2016), commented that because turbidity limit is 
not related to the specific flowrate (limit value is not normalized), the same criteria are valid for 
small and large volume flows with totally different impacts on receiving waters. In practice, most 
of the CL systems are equipped with a water treatment unit for the bleed-off, while OL systems 
normally do not include water treatment and if included, treating only a part of the discharge 
flow leading to lower treatment efficiency than in CL systems. After comparing pollutant 
concentrations and volume discharge flows in OL and CL systems, Teuchies et al. (2020) 
reported lower total discharge of pollutants from CL operation than from OL operation (6 times 
for metals and 183 times for PAHSs). 
Local conditions and regulations for metals should be also considered. Table 4 presents a review 
on local regulations on wastewater for discharge of metals (Lahtinen, 2016), proposed limit 
values for EGCS discharge water (Norway and Finland, 2006) and measured metal 
concentrations found in the reviewed research studies (summarized in Table A-4). Based on 
information presented in Table 4 and the uncertainties in turbidity as a surrogate parameter, it 
might be convenient to established limit values for metals of environmental concern in EGCS 
discharge water, for instance for vanadium, nickel, copper and zinc, to safeguard the 
environmental protection of the receiving waters. 
Table 4: 
Limit values for metals from wastewaters set in local regulations, proposed limit 
values for EGCS discharge water as in document MEPC 55/4/7 and typical metal 
concentrations found in EGCS discharge water 
Compound | Proposed limit values ® 
(H8/L) 
Local limit values ” | Measured concentrations © 
Tier 1 | 
Tier 2 ' 
Tier 3 
| HSY | 
SV P95 | 
ADEC1 | ADEC2 
OL 
CL 
Chromium | NA | 
NA 
NA | 
100 | 50 
<0.9-31 
9 — 14 000 
Copper | 
ag | 
4| 2000| 
200 
] 87 | 130 | 
1-—-260 
10 —2400