Reverse Osmosis Desalination: Thermodynamic Restriction and Process Economics

Reverse osmosis (RO) membrane desalting is a leading technology for the production of potable water from saline water. Water production cost in a typical RO desalination plant consists of the cost of energy, equipment, membranes, labor, maintenance, chemicals, brine management, and financial charges. The energy consumption per volume of produced permeate (i.e., the specific energy consumption or SEC) may be a significant portion of the cost of RO desalting, depending on applied pressure requirements. In order to reduce process energy consumption and decrease the volume of generated concentrate stream (primarily for inland water desalination), product water recovery must be optimized while keeping the overall water production cost at a reasonable level. To meet this challenge, a multi-pronged approach to improving the efficiency of reverses osmosis desalination is needed. Overall, the analysis from this study suggests that significant reduction in the cost of RO water desalination can emerge from the development of membranes of greater fouling and scaling resistance, the optimization of process configuration and control schemes (e.g., to account for feed salinity fluctuation [6] and even temporal fluctuation of electrical energy purchasing price), utilization of low-cost renewable energy sources, as well as more effective and less-chemical intensive feed pretreatment and brine treatment

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