Effects of membrane orientation on permeate flux performance in a submerged membrane bioreactor Tsun Ho Lee and Stephanie Young
Abstract; Full Text (2063K) .	pages 141-149.	DOI: 10.12989/mwt.2012.3.3.141

Abstract
The aeration provided in a Submerged Membrane Bioreactor (SMBR) improves membrane filtration by creating turbulence on the membrane surface and reducing membrane resistance. However, conventional hollow fiber membrane modules are generally packed in a vertical orientation which limits membrane scouring efficiency, especially when aeration is provided in the axial direction. In the present research, 3 innovative hollow-fiber membrane modules, each with a different membrane orientation, were developed to improve membrane scouring efficiency and enhance permeate flux. Pilot testing was performed to investigate the permeate flux versus time relationship over a 7-day period under different intermittent modes. The results indicated that the best module experienced an overall permeate flux decline of 3.3% after 7 days; the other two modules declined by 13.3% and 18.3%. The lower percentage of permeate flux decline indicated that permeate productivity could be sustained for a longer period of time. As a result, the operational costs associated with membrane cleaning and membrane replacement could be reduced over the lifespan of the module.

Key Words
hollow fiber membrane; membrane orientation; permeate flux; membrane fouling; submerged membrane bioreactor; membrane replacement, operation, and maintenance; commercialization; membrane technology

Address
Faculty of Engineering and Applied Science, University of Regina, Regina, Canada

Gas sparged gel layer controlled cross flow ultrafiltration: A model for stratified flow regime and its validity Vivek Khetan, Ashish Srivastava and Sirshendu De
Abstract; Full Text (2053K) .	pages 151-168.	DOI: 10.12989/mwt.2012.3.3.151

Abstract
Gas sparging is one of the techniques used to control the concentration polarization during ultrafiltration. In this work, the effects of gas sparging in stratified flow regime were investigated during gel layer controlling cross flow ultrafiltration in a rectangular channel. Synthetic solution of pectin was used as the gel forming solute. The liquid and gas flow rates were selected such that a stratified flow regime was prevalent in the channel. A mass transfer model was developed for this system to quantify the effects of gas flow rates on mass transfer coefficient (Sherwood number). The results were compared with the case of no gas sparging. Gas sparging led to an increase of mass transfer coefficient by about 23% in this case. The limitation of the developed model was also evaluated and it was observed that beyond a gas flow rate of 20 l/h, the model was unable to explain the experimental observation, i.e., the decrease in permeate flux with flow rate.

Key Words
air sparging; stratified flow; gel layer; mass transfer coefficient; permeate flux

Address
Department of Chemical Engineering; Indian Institute of Technology, Kharagpur, Kharagpur – 721302, India

Modification of polyamide reverse osmosis membranes seeking for better resistance to oxidizing agents Lucinda F. Silva, Ricardo C. Michel and Cristiano P. Borges
Abstract; Full Text (3843K) .	pages 169-179.	DOI: 10.12989/mwt.2012.3.3.169

Abstract
One of the major limitations in the use of commercial aromatic polyamide thin film composite (TFC) reverse osmosis (RO) membranes is to maintain high performance over a long period of operation, due to the sensitivity of polyamide (PA) skin layer to oxidizing agents, such as chlorine, even at very low concentrations in feed water. This article reports surface modification of a commercial TFC RO membrane (BW30-Dow Filmtec) by covering it with a thin film of poly(vinyl alcohol) (PVA) crosslinked with glutaraldehyde (GA) to improve its resistance to chlorine. Crosslinking reaction was carried out at 25 and 40oC by using PVA 1.0 wt.% solutions at different GA/PVA mass ratio, namely 0.0022, 0.0043 and 0.013. Water swelling measurements indicated a maximum crosslinking density for PVA films prepared at 40oC and GA/PVA 0.0043. ATR-FTIR and TGA analysis confirmed the reaction between GA and PVA. SEM images of the original and modified membranes were used to evaluate the surface coating. Chlorine resistance of original and modified membranes was evaluated by exposing it to an oxidant solution (NaClO 300 mg/L, NaCl 2,000 mg/L, pH 9.5) and measuring water permeability and salt rejection during more than 100 h period. The surface modification effectively was demonstrated by increasing the chlorine resistance of PA commercial membrane from 1,000 ppm.h to more than 15.000 ppm.h.

Key Words
reverse osmosis; polyamide active layer; surface modification; chlorine resistance; poly(vinyl alcohol)

Address
Lucinda F. Silva and Ricardo C. Michel : IMA/UFRJ, Federal University of Rio de Janeiro, 21941-598, Rio de Janeiro, RJ, Brazil
Cristiano P. Borges : PEQ/COPPE/UFRJ, Federal University of Rio de Janeiro, 21941-970, Rio de Janeiro, RJ, Brazil

Progresses in membrane and advanced oxidation processes for water treatment Khulbe K.C., Feng C.Y., Matsuura T. and Ismail A.F.
Abstract; Full Text (398K) .	pages 181-200.	DOI: 10.12989/mwt.2012.3.3.181

Abstract
At present water crisis is not an issue of scarcity, but of access. There is a growing recognition of the need for increased access to clean water (drinkable, agricultural, industrial use). An encouraging number of innovative technologies, systems, components, processes are emerging for water-treatment, including new filtration and disinfectant technologies, and removal of organics from water. In the past decade many methods have been developed. The most important membrane-based water technologies include reverse osmosis (RO), ultrafiltration (UF), microfiltration (MF), and nanofiltration. Beside membrane based water-treatment processes, other techniques such as advanced oxidation process (AOP) have also been developed. Some unconventional water treatment technology such as magnetic treatment is also being developed.

Key Words
water treatment methods; waste-water; membranes for water treatment; advanced oxidation process (AOP); nanoparticles; pollutants

Address
Khulbe K.C.*, Feng C.Y.and Matsuura T. : Industrial Membrane Research Institute, Chemical and Biological Engineering Department, University of Ottawa, On., K1N 6N5, Canada
Ismail A.F.: Advanced Membrane Technology Research Center (AMTEC), Universiti Teknologi Malaysia, 81310 Skudai, Johor, Malaysia

Development of membrane blend using casting technique for water desalination A. EL-Gendi, S.S. Ali, S.A. Ahmed and H.A. Talaat
Abstract; Full Text (8922K) .	pages 201-209.	DOI: 10.12989/mwt.2012.3.3.201

Abstract
Membrane separation technologies have some of advantages are considered a better alternative to traditional methods. Research of novel membranes is very vital for covering the higher required of membrane in several purposes like water desalting technology. In this work polyamide-6/ cellulose acetate (PA-6/CA) blend membrane was developed according to the wet phase inversion system. The structures of the prepared membranes were examined by scanning electron microscopy (SEM). SEM images showed uniform particles distribution in the prepared membranes. Moreover, SEM images revealed that the membranes have relatively uniform surface (PA-6/CA). PA-6/CA blend membranes systems are evaluated by using synthetic NaCl solution. The separation performance showed that salt rejection increased with increasing of heat treatment of the casted films and it was improved with increasing of operating pressure.

Key Words
membrane blend; casting; desalination; polyamide; cellulose acetate

Address
National Research Center, Chemical eng., El Buhouth St., Dokki, Cairo, 12311 Egypt