A processing apparatus and method combines thin channel and nozzle technology, as well as cascading processing solution flow. The processing apparatus includes a base member that defines at least one opening which has a longitudinal axis that extends at an angle with respect to a horizontal axis, and at least one rack member which is removably insertable in the at least one opening. When inserted in the at least one opening, a processing path is defined between an inner surface of the opening and an outer surface of the rack member. The openings are configured so as to provided for a compact arrangement and the rack members are removable in a manner which facilitates maintenance and repair.