Effect of Permeate Flux and Tangential Flow on Membrane Fouling for Wastewater Treatment

Abstract

Well-controlled membrane filtration experiments were performed to systematically investigate the effect of permeate flux and tangential flow (crossflow) on membrane fouling. Results were analyzed by the resistance-in-series model where the reason for flux decline was subdivided into adsorption, concentration polarization, and reversible and irreversible fouling. A synthesized paper mill wastewater with mainly lignin and 2-chlorophenol, biological suspension (activated sludge), and their mixture were used as feed solutions for ultrafiltration (30 000 Da) and microfiltration (0.3 µm) at different concentrations. The filtration experiments demonstrated that permeate flux declined faster with increasing feed concentration and membrane pore size and with decreasing tangential flow. The biological suspension rather than wastewater quality was a major cause for permeate flux decline in membrane bioreactors. In the absence of permeate flux, filtration resistance by foulants adsorption was negligible, as compared to total filtration resistance in the presence of permeate flux. It was also shown that tangential flow had almost no effect on the decline rate of permeate flux at pseudo steady state. Membrane cleaning results revealed that, in the absence of tangential flow, permeate flux decline was dominantly caused by reversible fouling. On the other hand, tangential flow caused slightly higher irreversible fouling due to higher permeation drag, as compared to the case of absence of tangential flow. Autopsy of fouled membranes suggested that the irreversible fouling layer was initially formed by pore blocking of small particles followed by strong interaction of fouling layer with mainly dissolved materials and by fouling layer compaction due to permeation drag.

Department(s)

Civil, Architectural and Environmental Engineering

Keywords and Phrases

Bioreactors; Filtration; Flow of fluids; Fouling; Mathematical models; Pore size; Wastewater treatment; Water quality; Autopsy; Filtration resistance; Membrane bioreactor; Permeate flux; Resistance-in-series model; Tangential flow; Membranes

International Standard Serial Number (ISSN)

1383-5866

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2005 Elsevier Limited, All rights reserved.

Publication Date

01 Sep 2005

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