Organic ionic salt draw solutions for osmotic membrane bioreactors

This investigation evaluates the use of organic ionic salt solutions as draw solutions for specific use in osmotic membrane bioreactors. Also, this investigation presents a simple method for determining the diffusion coefficient of ionic salt solutions using only a characterized membrane. A selection of organic ionic draw solutions underwent a desktop screening process before being tested in the laboratory and evaluated for performance using specific salt flux (reverse salt flux per unit water flux), biodegradation potential, and replenishment cost. Two of the salts were found to have specific salt fluxes three to six times lower than two commonly used inorganic draw solutions, NaCl and MgCl2. All of the salts tested have organic anions with the potential to degrade in the bioreactor as a carbon source and aid in nutrient removal. Results demonstrate the potential benefits of organic ionic salt draw solutions over currently implemented inorganics in osmotic membrane bioreactor systems.

► Organic ionic salt solutions were investigated as draw solutions for osmotic MBRs. ► Specific salt fluxes were up to six times lower than commonly used inorganic salts. ► Organic anions are degraded in the bioreactor and available for nutrient removal. ► A method was found for determining the diffusion coefficient of ionic salt solutions.