Special Issue "Membranes and Water Treatment"

Guest Editor
Dr. Chuyang Tang
School of Civil and Environmental Engineering, Nanyang Technological University, 639798, Singapore
Website: http://www.cee.ntu.edu.sg/AboutCEE/Faculty%20Directory/Pages/EWRE_cytang.aspx
E-Mail: cytang@ntu.edu.sg
Phone: +65 6790 5267
Fax: +65 6791 0676
Interests: water treatment; wastewater reclamation; desalination; membrane separation; nanotechnology; surface and interfaces

Dear Colleagues,

Membrane separation is playing an increasingly important role in water treatment, wastewater treatment, water reclamation, and desalination applications. Pressure-driven microfiltration (MF), ultrafiltration (UF), and nanofiltration (UF) are used to remove a variety of contaminants from water and wastewater. These membranes have also been widely applied in industrial applications for water recycling and process intensification. Membrane bioreactors (MBRs) have great potential for more efficient treatment of wastewater with greatly reduced land footprint. Reverse osmosis (RO) is the main stream desalination technology with significantly lower energy consumption compared to thermal based processes. RO has also been adopted in many countries and regions for wastewater reclamation. Other membrane processes, such as electrodialysis (ED), membrane distillation (MD), forward osmosis (FO), are also finding their competitive edge in seawater and brackish water desalination.

Over the last few years, we have been witnessing a surge in membrane research for water applications. New materials and fabrication technologies have been developed and applied to novel membrane synthesis and modification. Examples include carbon nanotube based membranes, nanocomposite membranes, and biomimetic membranes. Novel membrane processes have been developed, and improved plant designs have been implemented. New hybrid membrane (membrane + X) processes have been reported. Many studies have also reported the use of renewable energy in membrane processes, particularly in the field of desalination. New control technologies against membrane fouling have been developed. These major breakthroughs lead the way to greatly enhanced process efficiency, reduced energy consumption and treatment cost, and many new exciting possibilities. This Special Issue offers a perfect site to document state-of-the-art developments and innovations. Authors are therefore invited to submit their latest results; both original papers and reviews are welcome.

Dr. Chuyang Tang
Guest Editor

Submission

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are refereed through a peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Membranes is an international peer-reviewed Open Access quarterly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 300 CHF (Swiss Francs). English correction and/or formatting fees of 250 CHF (Swiss Francs) will be charged in certain cases for those articles accepted for publication that require extensive additional formatting and/or English corrections.

• water treatment
• wastewater treatment
• desalination
• membrane processes
• membrane synthesis and modification
• contaminant removal
• membrane fouling

Type of Paper: Article
Title: Strategic Co-Location in a Hybrid Process involving Desalination and Pressure Retarded Osmosis (PRO)
Authors: Victor S.T. Sim ^1,2, Qianhong She ^1,2, Tzyy Haur Chong ², Chuyang Y. Tang ^1,2,*, Anthony G. Fane ^1,2 and William B. Krantz ^2,3
Affiliations: ¹ School of Civil & Environmental Engineering, Nanyang Technological University, Singapore
² Singapore Membrane Technology Center, Nanyang Environment and Water Research Institute, Nanyang Technological University, Singapore
³ Chemical and Biological Engineering, University of Colorado, Boulder, CO, USA
Abstract: This paper focuses on a Hybrid Process that uses feed salinity dilution and osmotic power recovery from Pressure Retarded Osmosis (PRO) to achieve higher overall water recovery. This reduces the energy consumption and capital costs of conventional seawater desalination and water reuse processes. The Hybrid Process increases the amount of water recovered from the current 66.7% for conventional seawater desalination and water reuse processes to a potential 80% through the use of reclaimed water brine as an impaired water source. A reduction of 12% to 36.4% in energy consumption is projected via the Hybrid Process. The attractiveness is amplified by potential capital cost savings of 12.9% to 20% compared to conventional designs of seawater desalination plants. A decision matrix in the form of a customizable scorecard is introduced for evaluating a Hybrid Process based on the importance of land space, capital costs, energy consumption and membrane fouling. This study provides a new perspective for looking at processes not as individual systems but as a whole utilizing strategic co-location to unlock the synergies available in the water-energy nexus for more sustainable desalination.

Type of Paper: Review
Title: Advancement in the Electrospun Nanofibrous Membranes—Synthesis, Modifications and Application in Water Treatment
Author: S A A Nabeela Nasreen and Seeram Ramakrishna *
Affiliation: NUS Centre for Nanofibers and Nanotechnology, National University of Singapore, 2 Engineering Drive 3, 117576, Singapore
Abstract: Water, one among the major resource available in the world, is under serious concern due to many factors like pollution, technology. Removal of the contaminants from water is the current focus inorder to regain those available water resources. Many techniques and methods were applied so far to treat the waste water from various sources like industries, human sewage and water from agriculture. Many materials like nanoparticles, polymers, simple organic compounds, inorganic clay materials in the form of thin film, membrane, as prepared material were employed for the treatment of water. Among these materials membrane technology plays a vital role in water treatment due to its easy handling and efficiency. Though many materials are in progress, nanofibers driven membrane are more valuable due to its high aspect ratio, more surface area and high porosity. Various composition and types of nanofibers were synthesised using simple technique like eletrospinning and this review article mainly focusess on those nanofibers synthesized by electrospinning, its chemical and physical modifications and its methodology in treating the water will be discussed.

Type of Paper: Article
Title: Successful Integration of Membrane Technologies in a Conventional Purification Process of Tannery Wastewater Streams
Authors: Marco Stoller ¹,*, Olga Sacco ², Angelo Chianese ¹, Diana Sannino ²
Affiliation: ¹ Department of Chemical Materials and Environmental Engineering, University of Rome "La Sapienza", Via Eudossiana 18, Rome 00184, Italy
² Department of Industrial Engineering, University of Salerno, Via Ponte Don Melillo, Salerno, Fisciano 84084, Italy
Abstract: The aim of this work is to design and integrate an optimized batch membrane process in a conventional purification process used for the treatment of tannery wastewater. The integration was performed by using two spiral wound membrane modules in series, that is nanofiltration and reverse osmosis, as substitutes to the biological reactor. The membrane process was designed in terms of sensible fouling issues reduction, which may be observed on the nanofiltration membrane if no optimization is performed. The entity of the fouling phenomena was estimated by pressure cycling measurements, determining both the critical and the threshold flux on the nanofiltration membrane. The obtained results were used to estimate the need of overdesign of the membrane plant as well as to define optimized operating conditions in order to handle fouling issues correctly for long period of time. Finally, the developed membrane process was compared, from a technical and economic point of view, with the conventional biological process, widely nowadays in use at tannery production sites and here proposed to be substituted by membrane technologies.

Type of Paper: Article
Title: Separation Properties of Detergent containing O/W Emulsion using MF/UF Ceramic Membranes
Authors: Kazuho Nakamura * and Kanji Matsumoto
Affiliation: Division of Materials Science and Engineering, Graduate School of Engineering, Yokohama National University, 79-5 Tokiwadai Hodogaya-ku, Yokohama 240-8501, Japan
Abstract: Washing systems using water soluble detergent are used in electrical and mechanical industries and the wastewater containing O/W emulsion are discharged from the systems. The membrane filtration has large potential for the efficient separation of O/W emulsion for reuses of treated water and detergent. The separation properties of O/W emulsions from detergent solution by cross-flow microfiltration and ultrafiltration were studied with ceramic MF and UF membranes. The effects of pore size (MWCO), applied pressure, cross-flow velocity, and detergent concentration on retention of O/W emulsion and flux were systematically studied. The O/W emulsion tended to pass through the membrane at the conditions of larger pore size, higher emulsion concentration, and higher pressure. And in these conditions the emulsion droplets having bigger emulsion size than membrane pore size passed through the membrane pore. These results imply the stability of O/W emulsion at membrane surface play an important role in the separation properties and the O/W emulsion could pass the membrane pore structure by destruction or deformation. At the condition achieving complete separation of O/W emulsion the limiting flux was observed and the flux behavior against operating condition was explained by gel-polarization model.

Type of Paper: Review
Title: Membrane Modification using Electron Beam and γ-Irradiation Technologies
Author: Agnes Schulze *
Affiliation: Leibniz Institute of Surface Modification, Permoserstr. 15, D-04318 Leipzig, Germany; E-Mail: agnes.schulze@iom-leipzig.de
Abstract: Membrane separation systems have gained increasing importance for many different applications, e.g., in hemodialysis, water treatment, gas separation, or proton conduction in fuel cells. The diverse applications require tailored properties, and therefore necessitate further modification to achieve polymer membranes with tailored properties, such as hydrophilized surfaces, hemocompatibility, mechanical stability, specific functionalities, permeation selectivity, or improved ion transport. The use of electron beam or γ-irradiation enables the modification of various different membrane materials by creating reactive species at the polymer chains for subsequent formation of inter- or intramolecular cross-links, grafting or chemical functionalization. Depending on the source parameters the emitted electrons can interpenetrate several centimeters. Therefore, these technologies can be used for the modification of the inner surface of membranes as well as for the bore of hollow fibers. This review summarizes the different modifications that have been developed using electron beam treatment or γ-irradiation for generating membranes with specific functions and properties for the desired applications.

Type of Paper: Review
Title: Pretreatment and Membrane Surface Modification to Reduce Membrane Fouling
Author: Junxia Liu, Huaqiang Chu and Bingzhi Dong *
Affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, Shanghai 200092, China
Abstract:The application of low pressure membrane (microfiltration/ultrafiltration) has undergone accelerated development for drinking water production. However, the major obstacle encountered in its popularization is membrane fouling caused by natural organic matter (NOM). This paper firstly summarized the two factors induced the organic membrane fouling such as molecular weight (MW) and hydrophilicity/hydrophobicity of NOM, and then introduced the methods preventing membrane fouling including pretreatment of the feed water (e.g., coagulation, adsorption, and pre-oxidation) and membrane surface modification (surface roughness, surface hydrophilicity, surface charge, etc.). Perspectives of further research are also discussed in this the literature.

Type of Paper: Article
Title: Performance and Long Term Stability of Mesorporous Silica Membranes for Desalination
Author: David Wang *
Affiliation: School of Chemical Engineering, The University of Queensland, Brisbane QLD 4072, Australia; E-Mail: d.wang1@uq.edu.au
Abstract: For the first time, sol-gel derived mesoporous amorphous silica membranes have been prepared on macroporous α-alumina tubular supports without the deposition of intermediate layers to reduce the membrane fabrication steps whilst improving the water flux and stability for desalination. The mesoporous silica xerogels were synthesized with various pH (6–9) via a two-step sol-gel process using tetraethyl orthosilicate in ethanolic solution by employing nitric acid and ammonia as co-catalysts. The membrane was tested for desalination for 0.3 to 15 wt% synthetic sodium chloride (NaCl) concentrations at feed temperature of 22 °C followed by long term membrane performance of up to 250 hours in 3.5 wt% NaCl solution. Results show that the water flux (and salt rejection) decreases with increasing salt concentration delivering an average value of 9.5 kg m-2 h-1 (99.6%) and 1.55 kg m-2 h-1 (89.2%) for the 0.3 and 15 wt% saline feed solutions, respectively. Furthermore, the permeate salt concentration was measured to be less than 600 ppm for testing conditions up to 5 wt% saline feed solutions, achieving below the recommended standard for portable water. Long term stability shows that the membrane performance is stable up to 150 hours and can still maintain excellent rejection of > 99%.