The disc separator is specially used for the two-phase and three- phase separation. The two-phase separation is to separate the suspended solid from liquid or two liquids which have the different specific gravity and are immiscible. The three-phase separation is to separate the two immiscible liquid phases and a phase of solid at the same time. 1. Liquid solid separation (i.e. separation of bottom concentration suspension), which is called clarification operation, that is two-phase separation.2. Liquid-liquid separation (or liquid-liquid-solid) separation (i.e., the separation of emulsion) is called separation operation,that is three-phase separation.