Microplastic Pollution in Ship-Sourced Wastewater: Assessment of Pollution Load Risk for Ballast and Bilge Water

The rapid development of maritime transport also causes a number of negative environmental impacts. One of these problems is marine pollution caused by the operation of ships. Pollution from ship sewage includes ballast water (BAL-W) and bilge water (BIL-W), which are regulated under International Convention for the Prevention of Pollution from Ships Annex IV. Both BAL-W and BIL-W samples were analysed in the study. Many of the microplastic (MP) particles detected in the BAL-W samples were micro sized, while the majority of MPs found in the BIL-W samples were macro (>0.5 mm) and micro (1 μm-<5 mm) in size. The findings show that MPs constitute the majority (53%) of the plastics analysed, followed by 25% mesoplastics and 11% nanoplastics (NPs). Plastics with a size class of 50-300 μm were most abundant in both BAL-W and BIL-W. For BAL-W and BIL-W sources, the average MP sizes were calculated to be 0.025-4.99±0.050 mm and 0.05-0.1±0.050 mm, respectively. Rubber/commercial (PNEU), polyethylene (PET) terephthalate, polystyrene (PS), and polyoxymethylene (POM) were the most abundant polymer types found in the BIL-W samples, accounting for 47.82%, 10.86%, 9.78%, and 6.55%, respectively, while PNEU and PE were the most abundant polymer types found in the BAL-W samples, accounting for 22.91% and 7.98%, respectively. The pollution load index was calculated 7.75 (Hazard Category IV) and 12.17 (Hazard Category V) for BAL-W and BIL-W waters. It is now clear that the BAL-W management system needs to be evaluated to eliminate MP pollution due to the presence of polymers in BIL-W and BAL-W.