As regards the olive pomace, today two kinds of process are mainly used to separate oil from olive pastes: the three-phase centrifugation system, which produces a relatively dry solid waste named three-phase pomace and a large volume of olive mill waste waters, and the two-phase system in which the extraction water injection is carried out only in the final vertical centrifugation step, reducing by one-third on average the volume of liquid effluent
[9].