Abstract: An electrodeionization polarity reversal apparatus is employed for the removal of dissolved salts from liquids. The preferred embodiment comprises the use of a fluid permeable filler of an equinormal mixture of anion and cation exchange material in both the ion-depleting and ion-concentration chambers while employing periodic symmetrical polarity reversal.

Abstract: An improved spiral-wound pressure membrane sorbent bed module is disclosed comprising a central permeate conduit around which said spiral is wound, said module also comprising a collection means for each membrane envelope in said module, said collection means communicating with the interior of said envelope along a substantial fraction of one edge of a permeate spacer in said envelope, all said collection means conveying permeate to the interior of said central permeate conduit at substantially the same cross-section of said conduit, the interior of said conduit containing sorbing means.

Abstract: Method and apparatus are disclosed for improving the anodic life of an electrode in an electrodialysis stack which electrode comprises at least in part an area which is anodic during at least part of the duty time of said stack, which stack also comprises an electrode compartment (chamber, cell, space) containing said electrode, a counter-electrode in a counter-electrode compartment and interior compartments between said electrode compartment and said counter-electrode compartment, which method and apparatus comprises:(a) introducing into said electrode compartment (and means therefor) a solution capable of forming a film on said area which is anodic during at least part of the operating time of said stack, which film is characterized by being electronically conducting and substantially refractory anodically, and(b) causing a film derived at least in part from said solution to be formed on said area which is anodic during at least part of the duty time of said stack (and means therefor) said film characterize