The solid-bowl decanter centrifuge is characterized by a horizontal conical bowl containing a screw conveyor that rotates in the same direction. Feed slurry enters at the center and is spun against the bowl wall. Settled solids are moved by the screw conveyor to one end of the bowl and out of the liquid for drainage before discharge, while separated water forms a concentric inner layer and overflows an adjustable dam plate. The helical screw conveyor pushing the deposited slurry operates at a higher rotational speed than the bowl.

A solid-bowl screw centrifuge was used to separate various types of algae (Mohn, 1980). Fed with an algal suspension of 2% solids, the separated algal slurry was able to attain 22% solids concentrations. Although the reliability of this centrifuge seems to be excellent, the energy con­sumption is too high. An attempt to concentrate an algae feed of 5.5% solids derived from a flotation process by a co-current solid-bowl decanter centrifuge was not successful (Shelef et al., 1984). Subsequently, algae slurry concentration was improved to 21% TSS by reducing the scroll speed to 5 rpm (Shelef et al., 1984). The solid-bowl decanter centrifuge was recommended for use concurrently with polyelectrolyte coagulant to increase the efficiency.