Although most separators are two-phase in design separating the gas and liquids, they can be built three-phase to separate natural gas, liquid hydrocarbons, and free water.

The design of the three-phase separator is the key to the successful running of an anaerobic granular-sludge expanded-bed (EGSB) reactor.

A modified UASB system with a new type of gas-liquid-solid separator was investigated with regard to its feasibility for the anaerobic treatment of brewery waste.