The bridge-supported clarifier pictured above is used for primary wastewater treatment. After large objects and grit have been screened out of the water, raw wastewater is fed into the primary clarifier. In this stage, floating material and material that easily settles out will be removed, resulting in a homogeneous effluent that can be further treated biologically in the secondary clarifier, and a sludge discharge that can be treated or processed.
In column support thickeners, such as the one shown below, the drive and raking mechanisms are attached to a central column. The feed usually enters through an overhead pipe supported by an access bridge that leads to the center column.