A band screen conversion apparatus for filtering water comprising a structural frame and a conventional endless loop of screens mounted for movement in a circuitous path defining two vertical generatrices through which the water may flow in a dual-flow configuration. Extending outwardly and forwardly from each side of the structural frame is a curving, gull wing arcuate baffle having a ledge which engages a vertical guide track defined by the side wall of the foundation. An upstream flow deflector plate extends across the width and height of the band screen apparatus, with a plurality of support struts extending outwardly and rearwardly from the front of the flow deflector plate and connected to the front edges of the arcuate baffles via brackets which are similarly engaged within the guide tracks thus transferring the differential loads directly to the well guide tracks and side walls. A pair of directional fins are pivotally mounted at the rear of the band screen apparatus which may be locked in one of several preselected orientations, including a retracted position for installation where the directional fins do not project outwardly from the structural frame.