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1 , An electrodialysis cell consists of a sand~ich of alternating cation and anion permeable membranes. Upon the application of an electric current, the positively charged ions (such as sodium) pass through the cation permeable membranes and the negatively charged ions (such as chloride), move in the opposite direction and pass through the anion permeable mem- branes. The ~ater in the center chamber of each membrane sandwich is thus depleted of salt ~hi1e the water passing through the intervening pairs is enriched. Last year, Coalinga, California, installed a small 28,000 gallon per day plant utilizing this process to convert their brackish well water to fresh and thus were able to cut their ~ater bill to $1.45 per thousand gallons. This process ~i11 be tested in the third demonstration plant which ~i11 be located at Webster, South Dakota. The plant will be designed to produce 250,000 gallons of fresh water per day. The cost of the converted ~ater ~i11 be somewhat less than $1.00 per thousand gallons. The fourth demonstration plant will be located at Ros,,'ell, Ne<< Mexico. It will utilize a forced-circulation vapro-compression distillation system designed to produce 250,000 gallons of fresh <<ater per day. , In a forced-circu1ation vapor-compression plant the saline water is .t'__.......~ ..... ...\..___._t.. ~ .....t... _ \....._..:1, ~ ._.!..\.. ____ ~_ __.3 'l._.... l.~.r__ ~_^_......:........ .F.......... -..---- -t" _....~...O'. ... ............... ...................J .......... .....r..... ......~ ........- "__0.- ----0--.0 --~... . the top of the tubes. The vapor is pumped off, and compressed, thus raising its temperature, and returned to the heating side of the evaporator tubes as the principal heat source of the plant. This process achieves very high heat use efficiency requiring only a small amount of supplemental heat to start the plant and to offset normal heat losses. lVith this system a pound of fuel oil <<ill produce 200 or more pounds of distilled water as compared to a single-effect distillation system <<here a pound of fuel will only produce about 15 pounds of distilled water. The fifth demonstration plant will be located at a yet to be selected site on the east coast. It ~i11 utilize a freezing process. An ice crystal is pure water, but when sea water freezes the salt crystals are trapped be- tween the ice crystals. The problem is to economically separate the pure water ice crystals from the salt. Last October we began operating a 15,000 gallon per day pilot plant at the Carrier Corporation Plant in Syracuse, New York, In this pilot plant an ice brine slush is formed by spraying pre-cooled sea water into a vacuum chamber. The slush is pumped into a tall column where the ice floats to the top through a dOWllward current of water that washes it free of salt. The ice is scraped into a tank where coils containing the incoming sea water cause it to melt and which in turn cools the sea water before it is sprayed into the vacuum chamber. G-7