Dialysis in double-pass cross-flow rectangular membrane modules with external recycle for improved performance Ho-Ming Yeh
Abstract; Full Text (671K) .	pages 75-89.	DOI: 10.12989/mwt.2011.2.2.075

Abstract
The predicting equations for mass transfer rate in cross-flow rectangular dialyzers with double flow and recycle, have been derived by mass balances. The recycling operation has two conflicting effects. One is the desirable effect of the increase in fluid velocity, resulting in an increased mass transfer coefficient. The other is the undesirable effect of the reduction in concentration difference due to remixing, resulting in decreased mass-transfer driving force. In contrast a single-pass device without recycling, considerable improvement in mass transfer is achieved if the cross-flow rectangular dialyzer of same size is operated with double pass and external recycling. It is concluded that recycle can enhance mass transfer, especially for larger reflux ratio.

Key Words
dialysis; external recycle; cross-flow; rectangular module; performance improved

Address
Energy and Opto-Electronic Materials Research Center,Department of Chemical and Materials Engineering,
Tamkang University Tamsui, Taipei County, Taiwan 251

Separation and flux characteristics in cross-flow ultrafiltration of bovine serum albumin and bovine hemoglobin solutions Ruey-Chang Hsiao, Chia-Lin Hung, Su-Hsia Lin and Ruey-Shin Juang
Abstract; Full Text (1718K) .	pages 91-103.	DOI: 10.12989/mwt.2011.2.2.091

Abstract
The flux behavior in the separation of equimolar bovine serum albumin (BSA) and bovine hemoglobin (HB) in aqueous solutions by cross-flow ultrafiltration (UF) was investigated, in which polyacylonitrile membrane with a molecular weight cut-off (MWCO) of 100 kDa was used. BSA and HB have comparable molar mass (67,000 vs. 68,000) but different isoelectric points (4.7 vs. 7.1). The effects of process variables including solution pH (6.5, 7.1, and 7.5), total protein concentration (1.48 and 7.40

Key Words
separation; bovine serum albumin; bovine hemoglobin; cross-flow ultrafiltration; specific cake resistance.

Address
Ruey-Chang Hsiao:Department of Chemical and Material Engineering, Lung Hwa University of Science and Technology,
Taoyuan 333, Taiwan
Chia-Lin Hung and Ruey-Shin Juang:Department of Chemical Engineering and Materials Science, Yuan Ze University, Chung-Li 32003, Taiwan
Su-Hsia Lin:Department of Chemical and Materials Engineering, Nanya Institute of Technology, Chung-Li 320, Taiwan

Multi-Dimension Scaling as an exploratory tool in the analysis of an immersed membrane bioreactor A.Bick, F.Yang, S.Shandalov, A.Raveh and G.Oron
Abstract; Full Text (1388K) .	pages 105-119.	DOI: 10.12989/mwt.2011.2.2.105

Abstract
This study presents the tests of an Immersed Membrane BioReactor (IMBR) equipped with a draft tube and focuses on the influence of hydrodynamic conditions on membrane fouling in a pilot-scale using a hollow fiber membrane module of ZW-10 under ambient conditions. In this system, the cross-flow velocities across the membrane surface were induced by a cylindrical draft-tube. The relationship between cross-flow velocity and aeration strength and the influence of the cross-flow on fouling rate (under various hydrodynamic conditions) were investigated using Multi-Dimension Scaling (MDS) analysis. MDS technique is especially suitable for samples with many variables and has relatively few observations, as the data about Membrane Bio-Reactor (MBR) often is. Observations and variables are analyzed simultaneously. According to the results, a specialized form of MDS, CoPlot enables presentation of the results in a two dimensional space and when plotting variables ratio (output/input) rather than original data the efficient units can be visualized clearly. The results indicate that: (i) aeration plays an important role in IMBR performance; (ii) implementing the MDS approach with reference to the variables ratio is consequently useful to characterize performance changes for data classification.

Key Words
aeration; cross-flow velocity; draft tube; Immersed membrane bioreactor; membrane fouling; multi-dimension analysis.

Address
A. Bick: Department of Industrial Engineering and Management, Jerusalem College of Technology, 21 Havaad Haleumi St., Jerusalem, 91160 Israel
F.Yang, S.Shandalov and G.Oron: J. Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Kiryat Sde Boker, 84990, Israel
A.Raveh: The school of business administration, The Hebrew University, Jerusalem, Israel

Development of a robust bench-scale testing unit for low-pressure membranes used in water treatment Haiou Huang, Kellogg Schwab and Joseph G. Jacangelo
Abstract; Full Text (8343K) .	pages 121-136.	DOI: 10.12989/mwt.2011.2.2.121

Abstract
A bench-scale test has recently been proposed as a predictive tool to minimize the scope of pilot-scale testing or to optimize the operation of full-scale membrane filtration systems. Consequently, a bench-scale testing unit was developed for this purpose and systematically evaluated in this study. This unit was capable of accommodating commercially available, low pressure, hollow fiber (LPHF) membranes with various configurations for testing under conditions comparable to real-world applications. Reproducibility of this unit in assessing membrane fouling and microbial removal efficiency of LPHF membranes was tested and statistically comparable results were obtained. This unit serves as a useful apparatus for academic researchers and utilities to evaluate the performance of LPHF membranes used for water treatment.

Key Words
bench scale membrane testing unit; low pressure; hollow fiber membrane; membrane fouling; membrane integrity; virus removal.

Address
Haiou Huang, Kellogg Schwab and Joseph G. Jacangelo: Johns Hopkins University, Center for Water and Health, Baltimore, MD 21205, USA