using results obtained f.mn qec&.ing experience of sea water concentration performed on large scale electrodialyzers in conjunction with technology for the continuous production of ion-exchange nenbranes, we have developed a nev type large scale electrodialyzer. This electrodialyzer has a high desalination ability and an efficient large capacity, and its perfo-ce is very effective. under nonaal operating conditions this electrodialyzer has a desalination ratio (concentration ratio of feed water to product) of 13.3 -desalinating percentage 92.5tand has a capacity of 5,370 n3/day. It features low scale fornation, lw electric power consrnption (1.1 l&T/m3 to desalinate a salt concentration of 3,000 ppm to 500 ppml and ease of naintenance, resulting in reduced plant construction and -ng costs. 1hTF.CDUCl'IO.Y Electrodialysis is recognized as an econonlcal process for desalinating brackish uater and has already been extensively employed. It is, however, still under development, and further inprovements canbe expected in thefuture ln pXtiCul~, electmdfalyzers have in the past heen design& .~+~wlly by various cocpanies and institutes in confonsity with the restrictions inposed by the material properties and size of the ion-exchange neobrane. which arc deternined by the particular manufacutring pmcess. And fmmtheoutset, no consideration whatsoever has been given to the question of how an electrodialyzer should essentially be designed. Currently e&sting electrcdfalyzers canbe roughly classified as sheetflovtypeor tortuouspathtype.