The Process and Water Quality Specialists
Understanding and selecting an appropriate desalting process train for a specific application is complicated with an assortment of desalination membrane technologies offered in today's market. Designing a reliable desalting system requires a technical firm that applies fundamental principles of water quality and chemistry to properly engineer a cost effective design.
Desalination membranes have become an important process in water purification and water reuse; transforming previously unavailable waters into a valuable resource. In water treatment today, desalination membranes are being widely applied for treating brackish surface waters, groundwaters, reclaimed wastewater and seawater to create new water sources, or restore degenerated water sources. Today, there are three types of membrane processes used to remove dissolved solids from water: reverse osmosis (RO), nanofiltration (NF), and electrodialysis (ED).
Two fundamental driving forces are used in these desalination membrane systems: pressure and electric potential. In pressure driven systems (RO & NF), the feed water is pressurized to exceed the osmotic pressure and water passes through the semi-permeable membrane; while dissolved solids are rejected and remain on the feedwater side, eventually concentrating into a brine solution. The systems driven by electric potential (ED) apply voltage to opposite ends of a membrane stack; one positive terminal and one negative. The charged ions are attracted to the terminal with the opposite charge (i.e. Na+ migrates toward the negative terminal and Cl- migrates toward the positive terminal). So, while the pressure driven system selectively passes water and retains dissolved salts, the electrically driven system extracts the dissolved salts and retains the water. Either way, the water and salts are separated producing low salinity water.