**2. Impact of bilge on marine pollution**

The regulation stipulated by the International Maritime Organization (IMO) highlighted on the oil content of the bilge water discharged to the sea. The International Convention for the Prevention of Pollution from Ships (MARPOL 73/78) has set the maximum limit of 15 mg/L for the oil content in the wastewater to be discharged to the sea. According to the US EPA (2008), passenger ships produce the highest amount of bilge water with huge difference as compared to the other types of ships. This is due to their more complex constructions and support for crowds of passengers [9].

Typically, the small volumes of treated bilge water are released above the water line and instantly diluted in the sea water. Hence, the obvious effects of oil spill is most likely not going to occur. However, a long-term effect might happen to the marine living organisms around the shipping lanes. The negative consequences that will take place may be due to the excessive concentration of biodegradable compounds, including oil, as well as continuous increment of nondegradable compound concentration such as metals [11].

Other than that, surfactant is one of the significant chemicals contained in the bilge water. The mixtures of oil and surfactants may cause higher toxicity since the oil and surfactants alone are toxic themselves. This may be due to the synergistic effects or the crude oil that has been dissolved, causing it to be consumable for the exposed organisms [12–15].
