Development of Improved Membranes for ROWPU Spiral-Wound Elements

Mobile reverse osmosis water purification units (ROWPU) have been used by the military for nearly 15 years. Although many improvements have been made in membrane, element, and unit operation during this period, several membrane problems remain that impair operational efficiencies. The membranes used in these systems possess intrinsic deficiencies that limit both element storage life and the operational life of the ROWPUs during field operations. specifically, these are: (1) fouling by suspended solids due to membrane surface roughness, (2) fouling by microorganisms due to chemical characteristics of the membrane surface, (3) membrane instability at elevated temperatures during both element storage and operation, and (4) chemical instability of the membrane which adversely affect the life and long-term performance of ROWPU elements. This Phase I program is designed to rectify these major membrane deficiencies by determining the feasibility for selection of monomers, both amines and acid chlorides, by computer modeling. Modeling will project the design, construction, properties, performance and interactions of the molecular Systems. The objectives are to locate aliphatic and aromatic monomers, when combined and reacted, will produce chemically and thermally stable membrane surfaces that are smooth to minimize fouling. Membrane surface roughness will be determined by Atomic Force Microscopy. Potential use of the proposed membrane improvements by the Federal Government, as well as U.S. membrane companies, should provide considerable cost savings in element replacement and increased efficiency in system operation due to minimized fouling and less frequent need for membrane cleaning. Effects of long-term storage also will be minimized.