Abstract:
The wide spread application of forward osmosis (FO) awaits substantial investigation in the
development of novel draw solutions. When surfactant monomers aggregate above the critical
micelle concentration (CMC) and Krafft temperature (Tk), micelles are formed. Micellar
solutions were evaluated as novel draw solutions for FO systems. It was found that the micellar
solutions generate stable water fluxes, independent of declining draw solution concentration,
around their CMCs. The reverse transport of different micellar solutions was found to be 53-268
times lower as compared to the sodium chloride, at similar molar concentrations. Upto 95 %
recovery of micellar solutions with energy efficient methods like ultra filtration (UF) or Krafft
temperature swing is another advantage. Microbial toxicity effects of the reverse transported
micellar draw solutions were studied using isolated microbial species and mixed activated
sludge. Micellar solutions were recommended for use in the forward osmosis membrane
bioreactor (FO-MBR) but with concentrations above CMC. Different operational parameters for
improving the efficiency of the FO-MBR were also optimized. A draw solution concentration of
2 M was found most suitable since the higher concentrations invited extensive concentration
polarization (CP) which caused a net water flux decline. Cross-flow velocity was optimized to
circulate the feed solution (sludge) in FO-MBR and the optimized value was 300 mL/min,
because greater velocities caused a breakdown of flocs to encourage severe membrane fouling.
Micellar fouled FO membranes were found to show 100 % flux recovery after cleaning with
Ethylenediaminetetraacetic acid (EDTA) solution. It was discovered that the major transport of
organic contaminants and draw solute, across the FO membrane, occurs in the first hour of
operation of the FO-MBR. In short, micellar solutions can be considered as a reliable draw
solution to the development of FO system
