An apparatus, system and method for pumping gaseous fluid are described. The gas separator of the invention homogenizes at least a portion of produced well fluid and vents unhomogenized gas, improving the efficiency and decreasing the downtime of the assembly. A system for pumping gaseous fluid from an underground well includes a gas separator, the gas separator including an impeller configured to homogenize at least a portion of a gas and a liquid in a pumped fluid to obtain homogenized fluid, the impeller including a top side open to the diffuser and a truncated vane located at a mid-pitch location between at least two untruncated vanes starting from a bottom side of the impeller, and a gas separation chamber downstream of the impeller, the gas separation chamber configured to vent an unhomogenized gas, and a centrifugal pump arranged to receive the homogenized fluid from the gas separation chamber.