Algae Dewatering with Different Draw Solutions and Cross Flow Velocities Using Forward Osmosis (FO) Flat Sheet Membrane

Forward osmosis (FO) is an innovative membrane separation technology which has been used in wastewater treatment and food processing, and can be extended to algae dewatering for further bioproduct processes. Experimental trials on algae dewatering using a FO system have already been initiated (e.g., NASA OMEGA project). The FO system can reduce the volume of water containing algae o assists consecutive biomass processes. While FO can reduce energy consumption and produce diluted draw solutions (DS) that can directly be used for irrigation or desalination. The objective of this study is to evaluate FO as means of algae dewatering in terms of different Cross flow velocity (CFVs) and different types of draw solutions (NaCl, KCl and NH4Cl). The DSs used in this study were selected based on availability and their ability to be used without regeneration. CFV was used as a main variable in controlling biofouling formation and concentration polarization. A semi-permeable aquaporin ployethersulfone (PES) FO membrane with an active surface area of 0.00125 m2 was used for the dewatering algae water and concentrate Chlorella vulgaris. It was found that, as a CFV increased, a membrane flux was slightly increased with less noticeable biofouling. For 1 M of DS concentrations, NH4Cl showed a higher flux than NaCl and KCl. The aquaporin PES FO membrane used in this study was compatible with the three DSs with fluxes ranging from 4-6 L/m2˙h. The extended experiment demonstrated a low flux loss of 0.018 L/m2˙h.