Analysis And Treatment Of Wastewater From Shipborne Magnesium Base-seawater Flue Gas Desulfurization

The pollution caused by sulfur dioxide discharged from shipborne flue gas increases with the development of shipping continuously. In order to meet the stringent requirements set down by the International Maritime Organization (IMO) on the shipping environment, more and more attention is paid to the research on shipborne flue gas desulfurization. However there has been relatively little research on shipborne desulfurization wastewater treatment. It is urgent to analyze and treat wastewater from shipborne flue gas desulfurization.When the main engine of the ship is being the normal operation, a self-made wet-method flue gas desulfurization (FGD) equipment with MgO-seawater as desulfurizer was applied on a container ship. When the desulfurization efficiency is more than90%, the wastewater sample was taken and the relevant water quality indicators of 《Exhaust gas cleaning system guide (2009)》(MEPC.184(59) resolution) was analyzed. According to the characteristics of the wastewater, a method of pre-aeration and activated carbon adsorption was applied to treat the wastewater.The main characteristics of the yellow and slightly pungent alkaline wastewater were obtained as follows:the value of pH was8.87, the turbidity was50.2FTU, the contents of sulfite, suspended solids(SS), CODOH-KI, polycyclic aromatic hydrocarbons (PAHs), nitrite and nitrate were10.21mg/L,1.471×104mg/L,224mg/L,370.6μg/L,1.56mg/L and9.28mg/L, respectively. The wastewater has high contents of sulfite and chloride, and the contents of COD, SS and PAHs are greater than the values in the seawater turbidity sewage discharge standard and the exhaust gas cleaning system (EGC) in the wash water discharge standards related indexes.The results of wastewater treatment by pre-aeration and activated carbon adsorption were as follows:after the wastewater (250mL) aerated by1.5h and2h, the sulfite conversion efficiency was29.6%and29.7%respectively. The latter was only 0.1%greater than the former. From the economic point of view, the aeration time of1.5h is reasonable. The contents of CODOH-KI, PAHs, nitrite and nitrate were decreased to1lOmg/L,52.5μg/L,1.43mg/L and9.50mg/L respectively, and the value of pH was7.56, when1.5g activated carbon was used to treat the wastewater (50mL) in the aeration time of1.5h. The indicators meet all requirements of Exhaust Gas Cleaning System Guide (2009)(MEPC.184(59) resolution). The saturated adsorption capacity of PAHs/activated carbon is44.85μg/g.