Microbial toxicity effects of reverse transported draw solute in the forward osmosis membrane bioreactor (FO-MBR)

• Published in: Journal of membrane science Vol. 429; pp. 323 - 329
• Main Authors: Nawaz, Muhammad Saqib, Gadelha, Gabriela, Khan, Sher Jamal, Hankins, Nicholas
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15.02.2013; Elsevier
• Subjects: ammonium bicarbonate; ammonium salts; artificial membranes; bioreactors; calcium chloride; Chemistry; Colloidal state and disperse state; Draw solution; Escherichia coli; Exact sciences and technology; Forward osmosis; General and physical chemistry; magnesium; Membranes; microbial communities; Microbial toxicity; molecular weight; osmosis; oxygen; potassium; Reverse solute transport; sodium; solutes; sulfates; Surfactants; toxicity; Draw solution; Forward osmosis; Surfactants; Microbial toxicity; Reverse solute transport; Membrane reactor; Toxicity; Membrane; Osmosis; Solutes; Surfactant
• ISSN: 0376-7388; 1873-3123
• DOI: 10.1016/j.memsci.2012.11.057

Reverse transport of draw solute in an FO-MBR system can affect the microbial community and treatment efficiency. Eight commonly used inorganic draw solutes and four novel surfactant draw solutes were investigated for toxicity to Escherichia coli. A bench scale FO set-up with a flat sheet membrane was installed to measure the specific reverse solute transport (Js/Jw). Five different concentrations (0.005, 0.01, 0.025, 0.5 and 0.1M) of all 12 draw solutions were prepared. E. coli micro-organisms were allowed to react with these solutions for 16h at 35°C and agar plates were developed, incubated and bacterial colonies were counted. Chlorides of calcium and magnesium depicted more support to growth as compared to sodium and potassium. However, all four chlorides may be used without inhibitory effects in the FO-MBR. Ammonium bicarbonate solution could only be used with a pledge of oxygen. Sulfate salts of ammonium, sodium and potassium can potentially be used in the FO-MBR. Surfactants are suitable alternatives; due to the high molecular weight of micellar aggregates, they exhibit a value for Js/Jw which is 100–150 times lower than that for inorganic salts, but they should be used at concentrations above their critical micellar concentration (CMC). ► Draw solutes were investigated for toxicity to biomass in FO-MBR. ► NaCl, MgCl2, KCl, CaCl2, (NH4)2SO4, Na2SO4, K2SO4 are suitable for use in FO-MBR. ► NH4HCO3 can be used with high dissolved oxygen and adequate mixing in FO-MBR. ► Surfactants have 100–150 times low Js/Jw then inorganic draw solutes. ► Surfactants can only be used at concentrations above their CMC.