Means by which reverse osmosis desalting costs can be substantially reduced well. before the year 2000

Abstract

Examination of the market, state-of-the-art in current practice, and a well documented recent study agree on cost for sea water desalting by reverse osmosis which is approximately $4.00 per thousand gallons of purified water produced. At this cost one generally only produces, reliably, water to meet the rather lenient purity standard of less than 1000 mg/l total dissolved solids after demineralization and conditioning if the recovery fractions and membrane replacement frequency are to have any degree of respectability and acceptability. The study predicts that future “fully developed costs” will be approximately $1.00 per thousand gallons of purified water, largely on the basis of a substantial investment in time and money for research and development over a period of many years. The thrust of this paper is that present technological product, process, and engineering capability can be used in high recovery full two-stage systems to reduce these costs by 40% to approximately $2.60 per thousand gallons of purified water produced, with such conditioned water meeting the 500 mg/1 TDS and the 250 mg/1 chloride ion upper limits. This thesis is examined and illustrated in detail in several iterations, including sea waters containing 35,000 and 42,000 mg/1 TDS respectively. The above approach produces substantial savings in power requirements, membrane replacement and pre-treatment capital and operating costs which far outweigh the added capital amounts to be amortized. These improvements can be realized starting now with minimum development cost or effort. Further cost reductions to be achieved thereafter by research and development effort are also considered.