Operating experience of the Dhekelia seawater desalination plant using an innovative energy recovery system

Dhekelia Desalination Plant in Cyprus has been in operation for 7 years. It includes eight 5,000 m3/d seawaterreverse osmosis trains operating with Mediterranean seawater with a TDS content of 41,800 ppm, with water temperature ranging from 17°C to 32°C. The energy recovery system originally installed at the plant is the Francis turbine, which, at the time, was considered one of the most efficient and economical devices on the market. Since then, however, market forces to reduce operational costs, by cutting down energy consumption, led to the advent of new energy recovery systems. Today several systems are in operation which reduce the RO energy consumption. Apart from the versions of the Francis turbine and Pelton wheel they include the hydraulic turbocharger, work exchanger and pressure exchanger, all harnessing the pressure energy of the brine. In our effort to be competitive for the years to come we decided to convert our existing energy recovery system from Francis turbines to the pressure exchanger. This paper outlines how it was decided to go ahead with the pressure exchangers, and gives comparisons with other energy recovery methods, and describes our operating experience with the pressure exchangers.