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Membrane Water Treatment   Volume 8, Number 4, July 2017, pages 337-353
Effect of solids retention time on membrane fouling in membrane bioreactors at a constant mixed liquor suspended solids concentration
L. Hao, S. N. Liss and B. Q. Liao

Abstract     [Full Text]
    Membrane fouling at different solids retention times (SRT) (7, 12 and 20 days) was studied under well-controlled conditions in a laboratory-scale aerobic submerged membrane bioreactor under constant biomass concentration using a synthetic high strength wastewater. An increase in SRT was found to improve membrane performance and this correlated to changes in the total production of bound extracellular polymeric substances (EPS), and the composition and properties of bound EPS using X-ray photoelectron spectroscopy (XPS) and Fourier transform-infrared spectroscopy (FTIR) and floc sizes. A larger amount of total bound EPS was found at the lowest SRT (7 days) tested but the ratio of proteins (PN) to carbohydrates (CH) in bound EPS increased with an increase in SRT. Similarly, the quantity of soluble microbial products (SMP) decreased with an increase in SRT and the SMP PN/CH ratio increased with an increase in SRT. SMP concentrations positively correlated to the percentage of membrane pore blocking resistance. The quantity of total bound EPS and total SMP positively corresponded to the membrane fouling rate, while the PN/CH ratio in the bound EPS and SMP negatively correlated to the membrane fouling rate. The results show that both the quantity and composition of bound EPS and SMP and floc sizes are important in controlling membrane fouling.
Key Words
    membrane fouling; surface properties; solids retention time; extracellular polymeric substances; soluble microbial products
L. Hao and B. Q. Liao: Department of Chemical Engineering, Lakehead University, 955 Oliver Road, Thunder Bay,
P7B 5E1, ON, Canada
S. N. Liss: School of Environmental Studies and Department of Chemical Engineering, Queen

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