Abstract: A spiral wound module assembly comprising: a permeate collection tube, at least one membrane envelope wound about the permeate collection tube, an outer module housing, and at least one acoustic transducer located adjacent to the permeate collection tube. Several embodiments are disclosed including a stand-alone probe adapted for insertion into the permeate collection tube. In several other embodiments, one or more transducers are secured to the inner surface of the permeate collection tube.

Abstract: The present invention pertains to an apparatus and method for treating a solution of high osmotic strength, especially seawater and solutions of greater than 20 bar osmotic pressure, by passing the solution through a vessel containing spiral wound reverse osmosis or nanofiltration elements. The vessel contains at least three elements in series and at least two of these elements have standard specific fluxed that differ by at least 50%. The invention allows a more even flux distribution within a filtration system to be obtained, and it may advantageously be combined with variations en element construction and feed spacers.