Technical and Economical Evaluation of Desalination Processes for Potable Water from Seawater

At low pressure and temperature, water is easily vaporized under partial vacuum pressure. Desalination of seawater as source of potable water is globally considered as an applied reliable technology. At low temperature and pressure, the heat transfer process yield is higher than any normal process. Therefore, the rate of vaporization of seawater is much higher than any usual processes. The partial vacuum was generated by the steam passing through steam ejector. Multi effect desalination (MED) evaporators were employed and the vaporized mass steam from the seawater was used as steam for the next evaporator. In this process, for each kg of stream utilized about 2kg of pure condensate drinking water was obtained. Multi stage flash (MSF) desalination technology is the dominant technology in Persian Gulf area. Advanced technologies are applied for industrial use of water. Reverse osmosis (RO) is a membrane separation process operated at high pressure. Another membrane process is electro-dialysis (ED) which is used for desalination purposes. Total dissolved salts concentrations in seawater at inlet seawater and outlet stream of the desalination plant were 38 and 57 g/L, respectively. The concentrated brine solution can be separated from seawater for salt production. The market value for salt product from seawater is $30 per ton; that may assist to reduce the price of potable water to $0.44/m . The purpose of present work was to investigate the estimated costs of potable water per m ; for 3 3 several existing technologies with the aim of energy conservation for small, medium and large scale desalination plants to deliver potable water. The lowest price of $0.35/m of drinking water may be projected for the water 3 obtained from RO or freezing processes.