This report is submitted in fulfillment of Contract No. SAph 76690 ... Feb. 1, 1965. "EPA 842-R-67-001." "February 1967."

"A bench-scale experimental study was made to determine the practicality of partially demineralizing municipal wastewater by eletrodialysis. Using filtration alone and filtration followed by carbon adsorption as pretreatments, long-term runs were made with a municipal secondary effluent to determine scaling and fouling effects of the water upon the electrodialysis membranes. During these runs a study was made to determine how high a ratio of product rate to concentrate rate could be obtained without forming scale on the membranes. Some fouling of anion membranes occurred with filtration and carbon adsorption pretreatment; without carbon adsorption, fouling was much worse. Scale formation was not a problem at product to concentrate ratios of less than then. At time much higher ratios were obtained without difficulty. The results of these runs indicated that the total operating cost for a 10-mgd electrodialysis treatment plant might be less than 10 [cents] per 1,000 gal. Information is presented on the relative selectivity of the membranes for common ions in wastewater. Included are data on the long-term runs in which actual wastewater was used, and some data on laboratory prepared solutions. A theoretical discussion of selectivity is included."--Page ix.