State-of-the-art of reverse osmosis desalination

Throughout the world, water scarcity is being recognised as a present or future threat to human activity and as a consequence, a definite trend to develop alternative water resources such as desalination can be observed. The most commonly used desalination technologies are reverse osmosis (RO) and thermal processes such as multi-stage flash (MSF) and multi-effect distillation (MED). In Europe, reverse osmosis, due to its lower energy consumption has gained much wider acceptance than its thermal alternatives. This review summarises the current state-of-the art of reverse osmosis desalination, dealing not only with the reverse osmosis stage, but with the entire process from raw water intake to post treatment of product water. The discussion of process fundamentals, membranes and membrane modules and of current and future developments in membrane technology is accompanied by an analysis of operational issues as fouling and scaling and of measures for their prevention such as adequate cleaning procedures and antiscalant use. Special focus is placed on pre-treatment of raw water and post-treatment of brine as well as of product water to meet drinking and irrigation water standards, including evaluation of current boron removal options. Energy requirements of reverse osmosis plants as well as currently applied energy recovery systems for reduction of energy consumption are described and cost and cost structure of reverse osmosis desalination are outlined. Finally, current practices of waste management and disposal as well as new trends such as the use of hybrid plants, i.e. combining reverse osmosis with thermal processes and/or power generation are addressed.