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CONTENTS
Volume 5, Number 1, January 2014
 

Abstract
A pilot-scale hybrid membrane bioreactor (HMBR) for real municipal wastewater treatment was developed by adding biofilm carriers into a conventional membrane bioreactor, distribution and dynamic changes of the extracellular polymeric substances (EPS) and their roles in membrane fouling were investigated. The results showed that the concentrations of loosely bond EPS (LB-EPS) and tightly bond EPS (TB-EPS) in activated sludge, carrier biofilm and sludge cake layer have been increased significantly with the running time of HMBR, during operation of the HMBR, EPS demonstrated positive correlations with membrane fouling. Compared to TB-EPS, LB-EPS showed more significant correlations with sludge physical properties and specific resistance to filtration (SRF) in HMBR, and thus demonstrated that LP-EPS have a stronger potential of fouling than TB-EPS. It was also found that a lower organic loading in HMBR could result a significant increase in EPS concentration, which would in turn influence membrane fouling in HMBR. This critical investigation would contribute towards a better understanding of the behavior, composition and fouling potential of EPS in HMBR operation.

Key Words
extracellular polymeric substances (EPS); membrane fouling; hybrid membrane bioreactor (HMBR); wastewater treatment

Address
(1) Aining Zhang, Zhe Liu and Yongjun Liu: Xi'an University of Architecture and Technology, No. 13 Yanta Road, Xi'an, 710055, China;
(2) Yiping Chen: Institute of Earth Environment, Chinese Academy of Sciences, No. 10 Fenghui South Road, Xi'an, 710075, China;
(3) Peter Kuschk: Helmholtz Centre for Environmental Research-UFZ, Permoserstr 15, D-04318 Leipzig, Germany.

Abstract
Reverse Osmosis (RO) desalination has gained wide and increasing acceptance around the world as a straightforward undertaking to alleviate the alarming water crisis. An enhanced monitoring of the quality of the water feeding in seawater RO (SWRO) plant through the application of an effective pretreatment option is one of the keys to the success of RO technology in desalination plants. Over the past 10 years, advances in ultrafiltration (UF) membrane technologies in application for water and wastewater treatment have prompted an impetus for using membrane pretreatment in seawater desalination plants. By integrating SWRO plant with UF pretreatment, the rate of membrane fouling can be significantly reduced and thus extend the life of RO membrane. With the growing importance and significant advances attained in UF pretreatment, this review presents an overview of UF pretreatment in SWRO plants. The advantages offered by UF as an alternative of pretreatment option are compared to the existing conventionally used technologies. The current progress made in the integration of SWRO with UF pretreatment is also highlighted. Finally, the recent advances pursued in UF technology is reviewed in order to provide an insight and hence path the way for the future development of this technology.

Key Words
reverse osmosis; desalination; pretreatment; ultrafiltration; integrated membrane system; fouling; seawater

Address
(1) W.J. Lau, P.S. Goh and A.F. Ismail: Advanced Membrane Technology Research Centre (AMTEC), Universiti Teknologi Malaysia, 81310 UTM, Skudai, Johor, Malaysia;
(2) S.O. Lai: Chemical Engineering Department, Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, Jalan Genting Kelang, 53300 Kuala Lumpur, Malaysia.

Abstract
Papermaking tobacco sheet is an important reclaimed process for cigarette making. Traditionally, the pressure driven membrane was often used to isolate the effective compounds from the tobacco sheet extract. However, this method is difficult to remove small ionic compounds. Besides, membrane fouling is a major problem for effective use of these pressure driven membrane technologies. In this study, the electrodialysis process is used to removal the chloride ions and nitrate ions, thus the smoking quality of papermaking tobacco sheet extract can get improved. Three types of electrolytes (Na2SO4, NaCl and HCl) are chosen to prevent the generation of precipitation. The results indicate that 0.1 mol/L HCl at current density of 30 mA/cm2 is the optimal condition for the electrodialysis process. The removal rates of the Cl- and NO3- in tobacco sheet extract are 97% and 98.4%, respectively. The electrodialysis process cost was estimated to be 0.11 $/L. Naturally, electrodialysis is not only technological feasible, environmental-friendly and economical-attractive for tobacco extract treatment.

Key Words
papermaking tobacco sheet; tobacco extract; electrodialysis; ion-exchange membranes

Address
(1) Zenghui Zhang, Chenxiao Jiang and Yaoming Wang: Laboratory of Functional Membranes, School of Chemistry and Materials Science, University of Science and Technology of China, Hefei, Anhui,230026, People's Republic of China;
(2) Zenghui Zhang and Yue Zhao: Nano Science and Technology Institute, University of Science and Technology of China, Suzhou, Jiangsu, 215123, China;
(3) Shaolin Ge: China Tobacco Anhui Industrial Co., LTD, Hefei, Anhui,230088, People's Republic of China.

Abstract
A series of microporous PVDF membranes were prepared by isothermal immersionprecipitation of PVDF/TEP casting dopes in both soft and harsh coagulation baths. Morphologies of the membranes

Key Words
microporous membrane; PVDF; membrane distillation

Address
(1) Hsu-Hsien Chang, Chih-Hao Tsai, Hao-Cheng Wei and Liao-Ping Cheng: Department of Chemical and Materials Engineering, Tamkang University, New Taipei City, 25137 Taiwan;
(2) Liao-Ping Cheng: Energy and Opto-Electronic Materials Research Center, Tamkang University, New Taipei City, 25137 Taiwan.

Abstract
In this study, a theoretical model for the transport phenomena in an Air Gap Membrane Distillation used for desalination was developed. The model is based on the conservation equations for the mass, momentum, energy and species within the feed water solution as well as on the mass and energy balances on the membrane sides. The rarefaction impacts are taken into consideration showing their effects on process parameters particularly permeate flow and thermal efficiency. The theoretical model was validated with available data and was found in good agreement especially when the slip condition is introduced. The rarefaction impact was found considerable inducing an increase in the permeate flux and the thermal efficiency.

Key Words
water desalination; membrane distillation; air gap membrane distillation; slip velocity

Address
(1) Nizar Loussif: École Nationale d\'Ingénieur de Monastir, Université de Monastir, Monastir, Tunisie;
(2) Nizar Loussif: Unité de Recherche Matériaux, Energie et Energies Renouvelables,
Faculté des sciences Gafsa, Université de Gafsa, 2100 Gafsa, Tunisie;
(3) Jamel Orfi: Department of Mechanical Engineering, College of Engineering, King Saud University, Riyadh, Saudi Arabia.


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