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 
EGCS discharge water depends on several variables including EGCS design and operation, fuel 
and lube oil composition, engine load and conditions (quality of combustion), water treatment, 
water background concentrations and chemicals added. These variables can be grouped, so that 
three different pollutants sources are identified: the exhaust gas, the inlet water and the EGCS 
itself including the water processing (US EPA, 2011). For example, the corrosion of the system 
material may contribute to the presence of metals in the discharge water (Den Boer and Hoen, 
2015). Another factor affecting the concentration of pollutants is the water flowrate. In ports, 
harbours and estuaries, where the continuous engine power is considerably lower, some 
systems operate with reduced flow and some ships do not use EGCS at all in ports. Other 
systems operated at constant flow will obviously discharge a cleaner effluent (MEPC, 2008b), or 
more correctly, diluted pollutant concentrations at such conditions. At the end, the pollutants 
load discharge might be more relevant to evaluate environmental impacts than their discharge 
concentration. There are concerns about the environmental impact of EGCS, because of the 
amounts and components of the EGCS discharge water (Lange et. al, 2015). 
2.5 Current developments on the EGCS technology 
EGCS experts and manufacturers (Riviera and EGCSA, 2020) have expressed that the technology 
is already mature. However, current research and development activities are being carried out, 
for instance, to enhance particulate removal and CO, capture from the exhaust gas (Riviera and 
EGCSA, 2020; IOW, 2020). In the treatment of EGCS discharge water, there is still room for 
improvements, so that new filter and membrane types are being tested (Riviera and EGCSA, 
2020). For instance, the Flensburg University of Applied Sciences is currently carrying out a 
oroject to test a membrane plant for the treatment of bleed-off in CL systems (HS Flensburg, 
2020). Actually, most of the current developments on scrubber water treatment are focused on 
dleed-off from CL systems. The relatively great volume flowrates from OL systems make the 
technical feasibility of water treatment very complex. In fact, water treatment units in OL 
systems are uncommon. In this regard, the company Prime Lake has completed a pilot test using 
electro-aeration for elimination of harmful contaminants in water from OL systems (Hakirevic, 
2020). 
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