A method of retrofitting a filter plate including a filtration zone and a frame surrounding the filtration zone for use in a filter press. The frame of the filter plate is altered to removably receive a filtrate cartridge, the filtrate cartridge constructed and arranged to facilitate flow out of a filtration chamber of the filter press associated with the filtration zone to a discharge port. The filtrate cartridge is inserted in the frame. Related filter plates and filter presses are also disclosed.