AbstractThe productivity of ion exchange processes is usually limited by the diffusional process. The use of very fine mesh resins (down to 10–25 microns diameter) in very thin (ca 3–9 mm) beds supported on a microfiltration membrane of three micron pore diameter is described. These systems were used to process a simulated wastewater containing 4000 ppm of NaCl, plus some calcium and magnesium chlorides, as well as 0.2 ppm each of the metal ions Cu, Ni, Pb, Zn, and Cr (III). Regeneration with dilute HCl produced a concentrate of 1/1000 the volume of the feedwater trea