Test results on FT-30 eight-inch-diameter seawater and brackish water reverse osmosis elements

Abstract

Spiral-wound reverse osmosis elements formed of FT-30 membrane have been used for a variety of desalting applications around the world. The membrane was originally developed to satisfy the requirement for a true single-pass seawater membrane that would maintain its salt rejection characteristics while operating in a variety of seawater feeds. Later test results proved its applicability as a brackish-water desalting membrane as well, and FT-30 elements are now operating over a broad spectrum of feedwaters. ranging from tapwater to difficult industrial separations. The FT-30 membrane is noncellulosic and is of a thin-film composite configuration. It satisfies the main requirement of having high flux and excellent salt rejection, but in addition it is chemically stable, can operate over a broad range of pH, is partially resistant to chlorine exposure and shows good stability at high feedwater temperatures. These latter characteristics facilitate both acid and caustic cleaning, an important consideration under fouling conditions. Considerable field application experience has been obtained with FT-30 membrane elements over the past three years. This experience has given excellent results, although it has been limited to small elements -- the largest manufactured by FilmTec until recently was 4 × 21 inches and gave 600 gpd on seawater and 1200 gpd on brackish water. In early 1982 4- × 40-inch elements began to be produced and used commercially. Then in the summer of 1982, 8- × 40-inch elements were manufactured for the first time, meeting the design goals of single-pass seawater performance with product flows of over 5,000 gpd, and under brackish water conditions with flows of over 10,000 gpd. These large elements are now being tested on seawater and brackish water feeds in the MidEast, in England, in Florida, and in several other locations. Single-pass seawater performance data and brackish-water test results are presented. Eight-inch elements are now being produced in commercial quantities for use in large reverse osmosis installations.