A fluid purifying module including a monolithic container, a pretreatment filter, and a selectively permeable membrane treatment cartridge, respectively housed in an external cylindrical space and an internal cylindrical space of the container, communicating with each other via one or more passages in the vicinity of one axial end of the container. The external space communicates at the same end as the opposite axial end with a first connector orifice for feeding fluid to be purified to the pretreatment filter, and the internal space communicates separately, at the same end as the aforementioned axial end, with a second connector orifice for evacuating from the module a flow of permeate (purified fluid) and with a third connector orifice for evacuating from the module a flow of retentate (residual fluid).