Abstract
This study investigated filtration behaviors of polysaccharides solutions, both alone and in mixture with proteins, in the short-time constant flux filtration with the focus on factors affecting the transmembrane pressure (TMP) increase rate, the irreversible filtration resistance, and the membrane rejection behavior. The results showed that the TMP increase rates in the short-time constant flux filtration of alginate solutions were significantly affected by the calcium addition, alginate concentration, and flux. Although the addition of calcium resulted in a decrease in the TMP increase rate, it was found that the irreversible fouling developed during the filtration increased with the calcium addition, implying that the double-sided effect of calcium on membrane filtration and that the TMP increase rate observed in the filtration does not always reflect the irreversible membrane fouling development. It was also found that for the filtration of solutions containing mixed alginate and BSA, alginate exerted a dominant effect on the TMP increase rate and the membrane exhibited a reduced rejection to both alginate and BSA molecules compared to that in the filtration of the pure alginate or BSA.
Highlights
The applications of membrane bioreactors (MBR) technology in municipal and industrial wastewater treatment have been expanded in recent years
Measurement of zeta potential will aid in prediction of long-term colloidal stability of the macromolecules in the concentration polarization (CP) layer formed on the membrane surface
This study showed that for the short-time constant flux filtration of alginate solutions, the transmembrane pressure (TMP) time profiles can be characterized by a non-linear TMP rise, followed by a linear
Summary
The applications of membrane bioreactors (MBR) technology in municipal and industrial wastewater treatment have been expanded in recent years. Membrane fouling still remains a critical factor affecting the capital and operational costs of MBRs. In the case of wastewater treatment, mixed liquor contains flocculated bioactive suspended solids, colloidal and soluble microbial products (SMP) as well as dissolved inorganic substances. Current fouling control strategies such as air scouring and flux regulation are proven to be effective to control cake formation and concentration polarization in MBRs. SMPs that are mainly composed of polysaccharides and proteins, are regarded as a major foulant affecting long-term membrane fouling in MBRs under air scouring and controlled flux condition [1,2,3].
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