ULTRAFILTRATION PLANT

UF Description 

In a GREENSIGN UF the hollow fibers are only 1.3 mm O.D. x 0.7 mm ID and are made from H-PVDF polymer ( H=hydrophilic). These fibers have high resistance to chemicals, heat, and fouling, and are mechanically strong. In the modular design, the hollow fibers are bundled inside a PVC shell, ranging in size from 6.5” to 8.9” OD. These modules are positioned vertically on a skid to form a UF rack that can be pre-piped and pre-wired and ready for installation on-site. (Note: Dow UF is shown for the sake of consistency throughout this discussion. Other brands of UF will vary in design and procedures.) In addition to the hollow fiber modular design, UF is also sold in flat sheet, spiral-wound, plate-and-frame, tubular module, and loose fiber bundle configurations.

Since the filtration flow path in a Dow UF hollow fiber is outside-to-inside, the contaminants from the feed will accumulate on the outside of the fibers, much like a cartridge filter that is familiar to all water purification. The purified water will flow through the center of the hollow fiber to be collected at the top of each module as filtrate. The outside-in flow as opposed to inside-out has the advantage that the contaminants have more area on the outside of the fiber on which to accumulate, thereby extending the run time between backwashes and cleanings. Also, with flow on the outside and with a vertical design, an air-scour bubbling (upward through the shell on the outside of the fibers) can be used to shake particles loose from the fibers prior to backwash cleanings. So, unlike a cartridge filter in which the elements have to be replaced when they are loaded with contaminants, the UF has permanent elements (hollow fibers) that can be cleaned by backflushes, air scouring, and eventually by stronger CIP operations. This gives the UF a long service life, finer filtration, and much less maintenance than a replaceable filter element.