Abstract: The present invention features a device for treating liquid including a containment member comprised of rigid porous polymer configured to form a containment space. Nonbonded particulate media is disposed in the space in contact with and contained by the containment member. Pores in the containment member are characterized by pore paths and pore sizes effective to permit flow of liquid through the pores while preventing the media from traveling through the pores. The containment member may be in various shapes and include different numbers of components. One variation of the containment member includes first and second containment layers comprised of the rigid porous polymer, which are configured and arranged so as to form a space therebetween in which the media is contained. Another variation of the containment member includes first and second porous polymer tubes forming a space in which the media is contained. Also featured is a method of using the device.