The invention relates to clarifying apparatus, such as settling tanks, provided with a bridge member which rotates in a horizontal plane above the suspension of solids being treated in the tank. The tank is free of any central supporting column for the bridge member and the bridge is supported at least at one end by the outer wall of the tank. A bridge support member, rigid with the tank, extends over the tank above the rotatable bridge member and provides a central pivot for rotation of the bridge member. The bridge support member may extend diametrically across the tank and may support the bridge member.