Keywords: DeSOx, ship exhaust gas, MgO, seawater, desulphurisation, washwater effluent, water quality analysis, washwater discharge criteria, water pollution, ship pollution prevention, sulphur dioxide emissions, chloride ions, sulphate ions, nitrate ions, suspended solids, magnesium hydroxide, magnesium sulphite, COD, chemical oxygen demand, total oil content, turbidity, shipping
Study on washwater effluent quality discharged by ship exhaust gas DeSOx system with magnesium and seawater desulphurisation method
The latest convention of ship pollution prevention was carried out by the International Maritime Organization (IMO), which requires that sulphur dioxide emissions from ships around the world must be further reduced. A novel wet scrubber system with MgO and seawater (M&S) as desulphuriser was proposed to deal with the new convention. The quality of the washwater effluent discharged by M&S DeSOx system has not been studied systematically yet. This paper used a variety of methods to analyse the effluent, including chemical method, spectrophotometry and X–ray diffractometer. The effluent was detected to contain a large amount of chloride, sulphate and nitrate ions, and the mass fraction of chloride ion was as high as 3.2%. The main components of suspended solids were magnesium hydroxide, magnesium sulphite, and silicon dioxide. In the effluent, COD, SS, total oil content and turbidity were above the limitation set by the washwater discharge criteria. Based on the analysis of the effluent quality, the sulphite, nitrite, PAHs and total oil content were regarded as the main factors affecting COD.