Yuma Area Office
Yuma Desalting Plant Operations
Reverse Osmosis
Multi-leaved reverse osmosis membranes used at the Yuma Desalting Plant are like an envelope sealed on three sides, with the open end wrapped around a perforated hollow pipe, or product water tube. Each membrane has three layers. The top layer is fabric (dacron sailcloth or pellon) coated with a material called cellulose acetate; the middle layer is a plasticized tricot (or knitted fabric); and the bottom layer is another sheet of cellulose acetate-coated fabric. Membranes are wound around the perforated hollow tube with a loose mesh called a brine spacer which is inserted between the envelopes. The rolled-up membranes are called membrane elements. These elements are loaded into fiberglass pressure vessels, which are large cylinders capped at the end. In the reverse osmosis process, pressurized salt water flows across the membrane surface of the cellulose acetate. The pressurized water causes water molecules to diffuse through the membrane, leaving the larger salt ions, and some salt-laden water molecules, behind. Once through the membrane, the desalted water is trapped within the cellulose acetate envelope, and it travels along miniscule grooves in the plasticized tricot toward the center of the element. There, it empties into the product water tube through evenly-spaced holes.
Reclamation is exploring ways of improving the reverse osmosis process. We are investigating different methods of preserving, storing, and rejuvenating membranes after they have been manufactured and/or used. We are also looking at new ways of filtering or cleaning water as much as possible before desalting it. Ourresearch effort also involves improving operational procedures to find a better way to desalt the water. Through this research, Reclamation hopes to reduce desalting costs and increase the safety and environmental compatibility of desalting technology.
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