Part 1 of this series compared spiral-wound electrodeionization(EDI) with more traditional plate-and-frame EDI. The plate-and-frame design is similar in construction to a plate heat exchanger with multiple fluid chambers sandwiched between a set of endplates (and electrodes). Within there are a series of cation and anion ion-exchange (IX) membranes. The spiral-wound design uses a pressure vessel more similar to reverse osmosis membranes.
This article examines the serviceability and EDI module life of the spiral-wound design. IX resin, feedwater requirements, power consumption, module pairing, and performance are among other topics that will be addressed.
Serviceability and Module Life
The spiral-wound EDI module offers the only serviceable EDI system in the market as the replacement of resins and/ or membranes is possible at anytime while reusing the housings, end caps, and titanium anode without difficulty reseal-ing. This unique feature dramatically reduces the operating cost by extending the useful life of the spiral-wound EDI modules. Therefore, reducing the high replacement cost for the conventional EDI modules can lower operating costs. The fact that resin replacement can be done in place of module replacement for about 1/10th of the cost of plate-and-frame stacks offers a reduction of operating costs over the life of the spiral-wound EDI module.