A solid-bowl screw centrifuge includes a rotatable drum having a horizontal axis of rotation, which drum surrounds a centrifuging space. Further included is a screw which is arranged within the drum, the screw being rotatable at a different speed relative to the drum. Further included is at least one liquid discharge sealed from its surroundings and at least one solid discharge in a tapering region of the drum. Also included is an immersion disk on the screw which disk lies between a liquid feed and the solid discharge and divides the centrifuging space into a discharge space between the immersion disk and the solid discharge, and a separation space between the immersion disk and the liquid discharge. The centrifuge includes a device for charging the separation space with a gas. A process for operating for the solid-bowl centrifuge is also disclosed.