Effects of surfactant addition to draw solution on the performance of osmotic membrane bioreactor

Abstract

This study investigated the effects of surfactant addition to the draw solution on the performance of osmotic membrane bioreactor (OMBR). Forward osmosis (FO) tests were conducted with the addition of sodium dodecyl benzene sulfonate (SDBS), a representative surfactant, to both inorganic and ionic organic draw solutions, including sodium chloride (NaCl), sodium acetate (NaOAc), and sodium propionate (NaPro), to determine the desirable draw solution for OMBR operation. Results show that SDBS impacts were more notable for inorganic draw solution in comparison to its ionic organic counterparts at the same osmotic pressure (60 bar) in FO operation. In specific, SDBS addition up to 5 mM considerably reduced the reverse diffusion of NaCl draw solute (approximately 69.7%) with insignificant impact on water flux. Thus, salinity build-up in the bioreactor could be effectively mitigated when SDBS was added to the NaCl draw solution in OMBR operation. This mitigation led to stable sludge characteristics and biological treatment to sustain OMBR performance regarding water production (approximately 10 L/m2h) and contaminant removal (e.g. over 90% for pharmaceutically active compounds).