SUMMARY In SWRO desalination process industries, the reduction of energy consumption constitutes one of the major thrust areas of research. The cost of energy in SWRO process is usually about 30 to 50% of the total production cost of water and can be as much as 75 % of the operating cost, depending on the cost of electricity. Excepting Jeddah and Al-Birk, all the SWCC SWRO plants are equipped with one or other type of energy recovery devices, which are utilized to recover an otherwise wasted energy in the reject. These energy recovery devices (ERD) are of varying efficiencies and their ability to recover the wasted energy is different in each case. ERD performance is very much dependant on the operating parameters such as flow as well as pressure, which of course is influenced by the feed water temperature. This report describes in detail the performance of several ERD systems used in various SWCC SWRO plants and compares their efficiencies with regard to the operation conditions for a period of one year and its effect on total energy saving and total power consumption by the high pressure pump in addition to the energy loss occurring in the process stream of SWRO plants. The average overall efficiency of ERD ranged from 3.2% for Haql to a maximum of 65% for Yanbu plant. Whereas the energy saving made of total energy consumed by the high pressure pump by ERD ranged from a meager 1.5% at Haql to a maximum value of 27.4% observed at Ummlujj. The average power consumed by the high pressure pump was in the range of lowest for Yanbu at 5.56 kWh/m 3 and highest was observed for Ummlujj plant of 7.93 kWh/m 3 . However, it was observed that a substantial amount of energy is lost by throttling that ranged from 6.4% the lowest
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