The ORUR01Handler should be able to handle OBX segments coming in with a datatype of ED. At this time, it simply throws an error and sends the HL7 to the error queue.
There is no need to do anything special here except for save the value in the transient complexData property on the rendered observation. ObsService.saveObs() will do the work of calling the related concept's handler to handle the data and fill in the persisted valueComplex property. We need to test this mechanism through the ORUR01Handler, because it may require hydrating concepts for observations.