**Abstract**

Discharging accumulated bilge water from the ship is very important in order to maintain its stability and safety. However, the bilge water that contains contaminants, including waste oils and oily wastes, must be treated prior discharging to the sea. The International Convention for the Prevention of Pollution from Ships (MARPOL) has set strict oil discharge limit in order to minimize sea pollution. Thus, an efficient oil–water separator must be installed to separate the oil from the bilge water. This chapter introduces and discusses the working mechanisms, as well as advantages and disadvantages of the available oil–water separation techniques for bilge water treatment, which include gravitational, centrifugation, flotation, coagulation and flocculation, biological processes as well as absorption and adsorption.

**Keywords:** bilge water, oil/grease, oil–water separation, centrifugation, flotation, coagulation and flocculation, biological
