Press Information

World's First 3-Stage RO Desalination Plant, Built by MHI, Begins
Supply of Highly Pure Water to Oil-Refining and Petrochemical Plant
In Rabigh, Saudi Arabia


Tokyo, May 29, 2008 - Mitsubishi Heavy Industries, Ltd. (MHI), has completed the construction of the world's first 3-stage reverse osmosis (RO) desalination plant in Rabigh, the Kingdom of Saudi Arabia. Employing the arrangement to serially connect three RO membrane units, this plant has an advantage in the construction of desalination plants, which produce low chloride ion concentrate water from seawater. MHI's new RO desalination plant requires shorter construction period and uses less energy in desalination compared with multistage flash evaporating method plants that have been widely used in the Middle East but require more energy for evaporation.

The new desalination plant, which has begun to supply water, is capable to supply 7,000 tons of high-quality and high-purity desalinated water per hour. The plant was delivered to the Independent Water, Steam and Power Project (IWSPP) company, which name is Rabigh Arabian Water & Electricity Company (RAWEC), that was jointly established by Marubeni Corporation, JGC Corporation, Itochu Corporation and Arabian Company for Water and Power Development Ltd. (ACWA Power), a local independent power producer. RAWEC will supply industrial-use water to Rabigh Refining and Petrochemical Co. (PetroRabigh), one of the world's largest joint ventures in integrated oil-refining and petrochemicals. PetroRabigh is equally owned by Saudi Aramco, a Saudi state oil company, and Sumitomo Chemical Co., Ltd. of Japan. Leveraging the commencement of operation of the world's first commercial 3-stage RO desalination plant, MHI will aggressively explore business opportunities stemming from the needs for desalination to highly pure water .

MHI succeeded in the commercialization of the 3-stage RO desalination plant using the company's abundant expertise accumulated in seawater desalination technology. The first stage RO membrane units are used to reduce chloride in seawater to produce brine water with 550mg/liter chloride ion concentration. The second and third stage RO membrane units further reduce the chloride ion concentration of brine water to 5mg/liter.

The evaporation method, which is conventionally used to produce highly pure water with less than 5mg/liter chloride ion concentration, is not energy efficient due to the method requiring thermal heat energy for vaporization and is thus less environmentally-friendly than the RO method. By applying the enhanced reliable RO membranes and developing a stable 3-stage direct coupling RO membrane process, MHI made it possible to introduce an epoch-making method to the future seawater desalination market including those for high pure water required in the petrochemical plants. Comparing with multistage flash evaporating method plants, MHI’s RO desalination plants have a remarkable advantage in construction period, construction cost and operation cost.

About MHI Group

Mitsubishi Heavy Industries (MHI) Group is one of the world’s leading industrial groups, spanning energy, smart infrastructure, industrial machinery, aerospace and defense. MHI Group combines cutting-edge technology with deep experience to deliver innovative, integrated solutions that help to realize a carbon neutral world, improve the quality of life and ensure a safer world. For more information, please visit or follow our insights and stories on