Chemical pollutants released in treated bilge water

Abstract

Bilge water is a complex cocktail of fresh- and seawater and of different organic and inorganic compounds. Each vessel produces between 50 to 7500 liters per day. Release of bilge water is regulated by IMO and the regulation is focusing on limiting the oil droplets in the bilge water below 15 PPM. New investigations into the composition of treated bilge water suggests that it contains more harmful substance's then just oil droplets. Especially different metals in concentrations above limit values. Samples of bilge water have been collected and investigated from six vessels in the Swedish merchant fleet, these samples are retrieved from two sampling points from each vessel. This, to be able to evaluate and compare the bilge water samples before and after that have been treated by an oil water separator. The results for treated bilge water, zinc is above the limit value by 124 times, nickel is 34 times over. This shows that metals exist in the bilge water, after treatment, and metals are above the limit value when it is released into the ocean. Quantities of surfactants are also released into the ocean with the bilge water, but these substances lack regulatory values. Because of the covid-19 pandemic samples were taken by the engineers onboard and not collected by the same engineers every time. This thesis only shows the results for six vessels and their separators all use the chemical method to treat the bilge water.