**3.6 Absorption and adsorption**

Physicochemical sorption involved in absorption and adsorption processes can eventually separate the oil from the bilge water. Absorption occurs when two discrete physical states of substances are fused together. Meanwhile, in adsorption, molecules adhere onto the surface of different phase [16]. Both absorption and adsorption involved absorbent sorption media and adsorbent, respectively. The oil is separated by pumping the bilge water through these media until their maximum sorption capacity is achieved, which then the oil is removed. Certain used media are possible to be regenerated onboard; meanwhile, some are regenerated or disposed of onshore. Somehow, the regenerated media is replaced once it is exhausted, where it can no longer absorb or adsorb the oil molecules. Having a few advantages which include low capital and operating cost as well as compact treatment unit, these two sorption techniques are suitable for vessels with less than 400 gross tonnages [16]. **Table 1** summarizes the comparison of the oil–water separation techniques.
