A comparison of the relative economics of sea water desalination by vapour compression and reverse osmosis for small to medium capacity plants

Abstract Lowest energy consumption is not necessarily the determining criterion for lowest cost sea water desalination. It is shown that at present-day market prices for plants, electrical energy and fuel oil, Vapour Compression plants with horizontal aluminium tubes—the “Ambient Temperature” Vapour Compression (ATVC)system—compares economically with Sea Water Reverse Osmosis (SWRO) even at the lowest net energy consumption achieved by the latter process by the use of high efficiency energy recovery turbines. This economic parity is shown to apply for plants of up to 4000 m3/day (1 mgd), and is shown to be maintained for future foreseeable developments resulting in reduced energy consumptions and more efficient plants. It is also indicated that more areas for potential improvements are available for ATVC, than for SWRO, which may result in more favorable economics for the former process in the future.