A rotary vessel for a filter assembly has a rotor body rotatable about an axis of rotation and a spigot with a non-circular cross-section and integral with or coupled to the rotor body. The spigot extends away from the rotor body along the axis of rotation and engages with a bearing. The spigot facilitates transfer of rotary motion between the rotor body and the bearing. A filter assembly has a housing with a main body and a closure member separably attachable to the main body. The rotary vessel is disposed inside the housing. The closure member retains the rotary vessel inside the housing and is separable from the main body to permit removal of the rotary vessel from the housing. The spigot integral with or coupled to the rotor vessel engages with a bearing of the filter assembly to rotatably support the rotary vessel in the housing.