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 harbour 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 acutely 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.

中文翻译：

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洗涤塔排放物对河口和港口水质的影响

背景

国际海事组织（IMO）对海洋运输燃料中的硫含量设定了限制。但是，船舶继续将这些残留的高硫燃料与废气清洁系统（EGCS或洗涤塔）结合使用。除了高硫，这些燃料的燃烧还会导致更高的污染物排放，包括金属和多环芳烃。在洗涤器中，用水喷射废气以去除SOx，从而在水生生态系统中排放出污染物浓度升高的酸性洗涤水。带洗涤塔的容器数量正在迅速增加，但是有关洗涤水质量和影响的知识有限。

结果

发现洗涤器洗涤水是酸性的，具有升高的浓度，例如锌，钒，铜，镍，菲，萘，芴和荧蒽。在情景高（20％的船只，浓度为90％的浓度）下，洗涤塔排放物对港口码头水质的影响的模型计算表明，例如萘的pH值降低了0.015个单位，地表水浓度却增加了（增加189％） ）和钒（增长46％）。

结论

IMO建立了硫法规，以减轻海事部门高硫排放的影响。但是，使用开环洗涤器作为减排技术不会降低其对海洋酸化的贡献。另外，不同类型的洗涤器排放的洗涤水对水生生物具有剧毒。但是，洗涤水被稀释了，在安特卫普（比利时）港口码头计算出的地表水浓度大大增加的化合物（萘>菲>芴> ena>钒）不是已经超过各自水质标准的化合物（WQS）。但是，码头和Scheldt河口已经超过了几种“优先有害物质”（水框架指令）的WQS。