Abstract

Performance of two inorganic divalent salts (CaCl2, and MgCl2) and two organic salts (CH3COONa and Mg(CH3COO)2) was compared with commonly used NaCl in an osmotic membrane bioreactor (OMBR) integrated with membrane distillation (MD) system. The system was investigated in terms of salinity buildup, flux stability, draw solution (DS) recovery and contaminants removal efficiency. Results indicated that organic DS not only lessen the salt accumulation within the bioreactor but also increase the pollutants removal efficiency by improving biological treatment. Among all draw solutions, NaCl and CaCl2 produced rapid decline in water flux because of high amount of salt accumulation in bio-tank as compared to other salts. The DCMD system successfully recovered all organic and inorganic draw solute concentrations as per OMBR requirement. Membrane flushing frequency for MD system followed the order as Mg(CH3COO)2 > CH3COONa > CaCl2 > MgCl2 > NaCl. More than 90% removal of COD, NH4+-N, and PO43−-P was achieved in the permeate for each salt because of the dual barriers of high retention membranes i.e., FO and MD.

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