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The current and the near-term thermal converters and the long-range fast breeders for seawater desalination are analyzed based on the fundamental principles, present technology and future development of nuclear reactors. By using the available data of light-water reactors, the trends of current and near-term thermal converters and long-range fast breeders are predicted and discussed. The unit plant cost, and the total nuclear power cost (consisting mainly of the fixed charge, the fuel cycle cost and the operating, maintenance cost) versus the cumulative and the net plant capacity (or reactor size) are respectively shown by curves. The first and the equilibrium core costs and the plant thermal efficiency versus the cumulative plant capacity are illustrated. The comparison of water cost versus net plant capacity and plant load factor for the single-purpose and the multipurpose nuclear desalting plants are also given. The feasibility and development of nuclear agro-industrial complexes and the vertical tube evaporators for desalting seawater technology are briefly discussed.

Multi-stage flash distillation and multiple effect boiling distillation are not entirely different processes, but the two ends of a continuum. The defining variable in the continuum is the rate of brine circulation relative to distillate product. The multi-stage flash “end” is characterised by morphological simplicity as compared with the MEB end which is morphologically complex. This simplicity is obtained at the cost only of increased circulation, i.e. pumping power. No water cost improvement is obtainable from the MEB system except by increasing performance ratio well beyond that achieved by multi-stage flash up to date. Multi-stage flash systems can be designed to give higher performance ratios also, and it is to this end that effort should be directed with greater acumen All argument for reversion to the MEB system is based on the assumption that in the VTE film boiling embodiment assured high heat transfer coefficients can be obtained and maintained in practice.

This study investigates economies associated with size of New England water utilities. Regression analysis techniques were applied to annual water cost and production data reported in the American Directory of Water Utilities (1968-1969). Modest economies of size in the production of water were found. Because in large communities more water is used per person, total cost increases at a slightly faster rate than population increases, but per unit costs of producing water decline. Substantial economies occurred when the number of customers was held constant and volume of water per customer increased. This study indicates possible economies when two or more of the many very small utilities combine activities to form a larger unit and by encouraging present customers to use more water.

The historical record of the cost of pumping groundwater in Arizona is examined. Measures used are the cost per acre-foot per foot of lift, the cost per acre-foot, the water cost per acre for important crops, and the total water cost per farm for representative general crop farms. Costs are presented in actual dollars and dollars adjusted by GNP implicit price deflators. Whereas pumping depths have been rising rapidly, costs per acre-foot per foot of lift have been falling, adjusted costs per acre-foot have been almost constant, and per acre costs and total farm costs relative to both total costs and total returns have fluctuated throughout the time period examined, sometimes being lower but often being higher than costs at the present time.

Dry-type cooling towers offer a solution to power plant siting problems related to thermal pollution and water supply. Dry cooling towers are being used successfully with steam electric generating plants in other countries (particularly in Europe) and in the United States. At present, only two small dry cooled electric generating units are operating in the United States but plans for a 200-mw dry cooled generating unit in Wyoming have been announced recently. The advantages of the dry cooling tower can be realized at a relatively low cost even if certain offsetting economies are not considered. All or part of the cost penalty related to dry cooling may be offset by fuel cost savings, water cost savings, transmission savings, or other savings resulting from the flexibility in plant siting permitted by the use of dry cooling systems.

Tig. 2. Economic Repair Point as a Function of Water Cost THE losses MATTER has received of a great water-system deal of losse has received a gr at deal of attention especially during the Northeast drought of 1961-66. Then, the paucity of water made some people aware that losses from major city systems, such as New York City's, were quite large and could constitute a major potential source of "new water." Data on the extent of municipal-system losses are difficult to find. The

RIASSUNTO La produzione di acqua dolce dall'acqua marina ha avuto inizio nell'era moderna con l'affermazione della propulsione navale a vapore. Il susseguente sviluppo della desalinizzazione dell'acqua marina per fornire acqua dolce sulla terraferma ha di necessita seguito lo stesso principio economico. E da attendersi che la desalinizzazione si affermi sempre piu per entrambi gli scopi. Nei primi tempi della desalinizzazione in impianti a bordo delle navi, una societa scozzese raggiunse una posizione eminente, e gran parte del contributo del Regno Unito allo sviluppo in questo settore avvenne attraverso di essa. Le prime esperienze erano tutte connesse con i sistemi di ebollizione mediante apparecchi a multiplo effetto. Notevoli anche le ricerche tendenti a impedire il formarsi di incrostazioni. Tali studi condussero alla costruzione del primo impianto di desalinizzazione sulla terraferma, ed ebbero il loro culmine con la realizzazione dei grandi impianti di Aruba e di Curacao negli anni 1955–57. In quegli stessi anni venne affermandosi il processo di evaporazione a piu stadi, che permette di ridurre drasticamente il costo dell'acqua dolce. Questo processo ha in seguito progredito rapidamente; ricerche per migliorarlo sono tuttora in corso in tutto il mondo. Oggi l'interesse e puntato, oltre che sulla distillazione, sull'elettrodialisi e su altre tecniche. L'A. discute nei particolari quanto sopra esposto, e indica le linee di sviluppo e i possibili risultati futuri. ABSTRACT The artificial production of fresh water from sea water began in the modern era with the coming of steam in marine propulsion. The subsequent development of desalination of sea water for fresh water supply on land has necessarily followed the same economic principle. We may expect to see desalination used more and more throughout the world. In the early days of ship board desalination plant, a Scottish company held quite a prominent place and much of the U. K. contribution to the development of this field was made through this industry. The early work was all concerned with the boiling system of distillation and considerable work was done to improve the thermodynamics of this by using multiple effects. There was also a substantial amount of work done on research into methods of preventing scale formation. Such knowledge led to the establishment of the first land based distillation plants. These reached their peak realisation in the installations in Aruba and Curacao, installed in the period 1955/57. These same years, however, saw the inception of the multi-stage flash process which dramatically reduced the water cost. Subsequent development of this process has been rapid and research to improve it still further is now active all over the world. Interest is active not only on distillation but on electrodialysis and other possible techniques. The paper covers in detail most of the matters summarised above, with indications of the new lines of work and the possible future outcomes. RESUMe La production de l'eau douce a partir de l'eau de mer est commencee dans l' âge moderne par l'emploi de la vapeur dans la propulsion des navires. La subsequente diffusion du dessalage de l'eau de mer pour fournir l'eau douce aux populations de la terre a suivi, par necessite, le mcme critere economique. Il faut s'attendre a ce que le dessalage s'affirme de plus en plus pour ces deux necessites. Aux premiers temps du dessalage effectue dans les installations a bord des navires, une societe ecossaise atteint une situation eminente et c'est pour la plupart grâce a elle que le Royaume Uni contribua au developpement de ce secteur. Les premieres experiences avaient ete effectuees toutes par les systemes d'ebullition a L'Aide d'appareils a effet multiple. A remarquer aussi les recherches pour empecher la formation d'incrustations. Ces etudes eurent pour resultat la construction de la premiere installation terrestre de dessalage et aboutirent a la realisation des grandes installations d'Aruba et de Curacao en 1955–57. Pendant ces mcmes annees s'affirma le processus d'evaporation a plusieurs etages, qui permet de reduire nettement le cout de l'eau douce. Ce processus a fait ensuite de progres considerables; dans le monde entier on est encore en train d'effectuer des recherches pour L'Ameliorer. L'interet se porte, maintenant, sur la distillation aussi bien que sur l'electrodialyse et sur d'autres techniques. L'A. examine en detail ce qu'il a expose ci-dessus et indique les nouveaux criteres de travail ainsi que les possibles futurs resultats.