The impact of scrubber discharge on the water quality in estuaries and ports

Abstract

Background: The International Maritime Organization (IMO) has set limits on sulphur content in fuels for marine transport. However, vessels continue to use these residual high sulphur fuels in combination with exhaust gas cleaning systems (EGCS or scrubbers). Next to high sulphur, combustion of these fuels also results in higher emissions of contaminants including metals and PAHs. In scrubbers, exhaust gases are sprayed with water in order to remove SOx, resulting in acidic washwater with elevated contaminant concentrations discharged in the aquatic ecosystem. The number of vessels with scrubbers is increasing rapidly, but knowledge on washwater quality and impact are limited. Results: The scrubber washwater is found to be acidic with elevated concentrations of e.g. zinc, vanadium, copper, nickel, phenanthrene, naphthalene, fluorene and fluoranthene. Model calculations on the effects of scrubber discharge under scenario HIGH (20% of vessels, 90th percentile concentrations) on the water quality in harbor docks showed a decrease in pH of 0.015 units and an increase in surface water concentrations for e.g. naphthalene (189% increase) and vanadium (46% increase). Conclusions: The IMO established sulphur regulations to mitigate the impact of high sulphur emissions of the maritime sector. However, the use of open loop scrubbers as an abatement technology will not reduce their contribution to ocean acidification. In addition, different types of scrubbers discharge washwater that is acute toxic for aquatic organisms. However, washwater is diluted and the compounds for which a large increase in surface water concentrations was calculated in the Antwerp (Belgium) harbour docks (Naphthalene > Phenanthrene > Fluorene > Acenaphthene > Vanadium) were not the compounds that already exceed their respective Water Quality Standards (WQS). Nevertheless, the WQS of several ‘priority hazardous substances’ (Water Framework Directive) are already exceeded in the docks and the Scheldt estuary. Since these hazardous substances are also identified in the washwater, scrubber washwater discharge should be discouraged in coastal waters and estuaries with large ecological value.

Severe Toxic Effects on Pelagic Copepods from Maritime Exhaust Gas Scrubber Effluents

“…Comparing to a list published by Teuchies and colleagues, our closed-loop EGSEs seem to contain PAHs at concentrations several times higher than the average ship, whereas heavy metal concentrations are slightly lower (except for Hg). 43 In our open-loop EGSE, PAH concentrations are close to the average, whereas metal concentrations seems lower than average, except Hg which was five times higher than average. 43 …”

“… 43 In our open-loop EGSE, PAH concentrations are close to the average, whereas metal concentrations seems lower than average, except Hg which was five times higher than average. 43 …”

“…While the intentions of the IMO may have been to find an environmentally sound solution to the sulfur problem, scrubbers effectively just function to move pollution from the atmosphere to the sea, thereby creating a suite of new unwanted environmental problems. 43 Moreover, allowing the use of scrubbers also economically incentivizes increased use of residual heavy fuel oils high in PAHs and heavy metals, with an accompanying increased environmental toll, instead of development of fuels with less environmental impact.…”

Polycyclic aromatic compounds (PACs) in oily wastewater from shipping with a focus on scrubber water

“…Despite the fact that the scrubber water has been used to wash the gases of combusted HFO (pyrogenic origin), there are several characteristics in the PAC ingerprint more resembling a petrogenic than a pyrogenic pro ile. This might be caused by an incomplete combustion of the HFO and/or the presence of oil from other oil sources, e.g., lubrication oil, in the scrubber water (Teuchies et al 2020).…”

A Novel Approach to Reduce the Environmental Footprint of Maritime Shipping

“…Recently several studies have raised concerns about a negative impact on the marine environment where authors pointed out how these guidelines look inappropriate and claimed for stricter regulations to control, in particular, for the emissions of persistent pollutants as PAH and heavy metals from seawater scrubbers (Turner et al 2017(Turner et al , 2018Ytreberg et al 2019;Dulière et al 2020). Teuchies et al (Teuchies et al 2020) showed that scrubber washwater emissions should be discouraged in areas with high levels of pollutions since the amount of emitted pollutants sum to the already polluted background. This conclusion holds true, however, for all the existing sources of pollutants active in that area.…”