Surfactant-Enhanced, Low-Pressure Membrane Desalination

Supply of potable water is essential for the individual soldier in hostile, marine, or wilderness environments. Chemical warfare agents and natural infectious bacteria can render water unusable unless filtered and/or disinfected, and high salinity cannot be tolerated by humans. Mainstream proposes to test the feasibility of ultrafiltration (UF)/nanofiltration (NF) surfactant-enhanced ion rejection for compact desalination. The advantages of UF/NF over heavily researched RO systems is operating pressure, which translates to reduced size and weight. Above the critical micelle concentration of surfactants, charged aggregates form in solution and at the membrane surface to bind/reject opposite charged species. Process have only been demonstrated with UF for a limited number of anions and cations with up to 99% rejection, but the technology has yet to be considered or applied to desalination. The surfactant-facilitated process has the potential for removal of heavy metal ions and also organic impurities by the same mechanism. Like RO, UF and NF will also disinfect the water stream since the molecular weight cutoff is still below that of bacteria and most endotoxins and pyrogens. The Phase I effort will culmiate in a proof-of-concept feasibility demonstratio of a 1-liter water purification system.