Special Issue "Membranes and Water Treatment"

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A special issue of Membranes (ISSN 2077-0375). This special issue belongs to the section "Membrane Processes (Applications)".

Deadline for manuscript submissions: closed (31 May 2013)

Special Issue Editor

Guest Editor
Prof. Dr. Chuyang Y. Tang (Website)

Department of Civil Engineering, The University of Hong Kong, Hong Kong, China
Fax: +65 6791 0676
Interests: water treatment; wastewater reclamation; desalination; membrane separation; nanotechnology; surface and interfaces

Special Issue Information

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 500 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.

Keywords

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

Published Papers (10 papers)

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Research

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Open AccessArticle Numerical Simulation of Particle Distribution in Capillary Membrane during Backwash
Membranes 2013, 3(4), 249-265; doi:10.3390/membranes3040249
Received: 18 July 2013 / Revised: 17 September 2013 / Accepted: 23 September 2013 / Published: 27 September 2013
PDF Full-text (1858 KB) | HTML Full-text | XML Full-text
Abstract
The membrane filtration with inside-out dead-end driven UF-/MF- capillary membranes is an effective process for particle removal in water treatment. Its industrial application increased in the last decade exponentially. To date, the research activities in this field were aimed first of all [...] Read more.
The membrane filtration with inside-out dead-end driven UF-/MF- capillary membranes is an effective process for particle removal in water treatment. Its industrial application increased in the last decade exponentially. To date, the research activities in this field were aimed first of all at the analysis of filtration phenomena disregarding the influence of backwash on the operation parameters of filtration plants. However, following the main hypothesis of this paper, backwash has great potential to increase the efficiency of filtration. In this paper, a numerical approach for a detailed study of fluid dynamic processes in capillary membranes during backwash is presented. The effect of particle size and inlet flux on the backwash process are investigated. The evaluation of these data concentrates on the analysis of particle behavior in the cross sectional plane and the appearance of eventually formed particle plugs inside the membrane capillary. Simulations are conducted in dead-end filtration mode and with two configurations. The first configuration includes a particle concentration of 10% homogeneously distributed within the capillary and the second configuration demonstrates a cake layer on the membrane surface with a packing density of 0:6. Analyzing the hydrodynamic forces acting on the particles shows that the lift force plays the main role in defining the particle enrichment areas. The operation parameters contribute in enhancing the lift force and the heterogeneity to anticipate the clogging of the membrane. Full article
(This article belongs to the Special Issue Membranes and Water Treatment)
Open AccessArticle Study of the Effect of Nanoparticles and Surface Morphology on Reverse Osmosis and Nanofiltration Membrane Productivity
Membranes 2013, 3(3), 196-225; doi:10.3390/membranes3030196
Received: 3 June 2013 / Revised: 24 July 2013 / Accepted: 6 August 2013 / Published: 15 August 2013
Cited by 3 | PDF Full-text (806 KB) | HTML Full-text | XML Full-text
Abstract
To evaluate the significance of reverse osmosis (RO) and nanofiltration (NF) surface morphology on membrane performance, productivity experiments were conducted using flat-sheet membranes and three different nanoparticles, which included SiO2, TiO2 and CeO2. In this study, the [...] Read more.
To evaluate the significance of reverse osmosis (RO) and nanofiltration (NF) surface morphology on membrane performance, productivity experiments were conducted using flat-sheet membranes and three different nanoparticles, which included SiO2, TiO2 and CeO2. In this study, the productivity rate was markedly influenced by membrane surface morphology. Atomic force microscopy (AFM) analysis of membrane surfaces revealed that the higher productivity decline rates associated with polyamide RO membranes as compared to that of a cellulose acetate NF membrane was due to the inherent ridge-and-valley morphology of the active layer. The unique polyamide active layer morphology was directly related to the surface roughness, and was found to contribute to particle accumulation in the valleys causing a higher flux decline than in smoother membranes. Extended RO productivity experiments using laboratory grade water and diluted pretreated seawater were conducted to compare the effect that different nanoparticles had on membrane active layers. Membrane flux decline was not affected by particle type when the feed water was laboratory grade water. On the other hand, membrane productivity was affected by particle type when pretreated diluted seawater served as feed water. It was found that CeO2 addition resulted in the least observable flux decline, followed by SiO2 and TiO2. A productivity simulation was conducted by fitting the monitored flux data into a cake growth rate model, where the model was modified using a finite difference method to incorporate surface thickness variation into the analysis. The ratio of cake growth term (k1) and particle back diffusion term (k2) was compared in between different RO and NF membranes. Results indicated that k2 was less significant for surfaces that exhibited a higher roughness. It was concluded that the valley areas of thin-film membrane surfaces have the ability to capture particles, limiting particle back diffusion. Full article
(This article belongs to the Special Issue Membranes and Water Treatment)
Figures

Open AccessArticle Temperature and Pressure Effects of Desalination Using a MFI-Type Zeolite Membrane
Membranes 2013, 3(3), 155-168; doi:10.3390/membranes3030155
Received: 16 June 2013 / Revised: 8 July 2013 / Accepted: 9 July 2013 / Published: 17 July 2013
Cited by 8 | PDF Full-text (1800 KB) | HTML Full-text | XML Full-text
Abstract
Zeolites are potentially a robust desalination alternative, as they are chemically stable and possess the essential properties needed to reject ions. Zeolite membranes could desalinate “challenging” waters, such as saline secondary effluent, without any substantial pre-treatment, due to the robust mechanical properties [...] Read more.
Zeolites are potentially a robust desalination alternative, as they are chemically stable and possess the essential properties needed to reject ions. Zeolite membranes could desalinate “challenging” waters, such as saline secondary effluent, without any substantial pre-treatment, due to the robust mechanical properties of ceramic membranes. A novel MFI-type zeolite membrane was developed on a tubular α-Al2O3 substrate by a combined rubbing and secondary hydrothermal growth method. The prepared membrane was characterised by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and single gas (He or N2) permeation and underwent desalination tests with NaCl solutions under different pressures (0.7 MPa and 7 MPa). The results showed that higher pressure resulted in higher Na+ rejection and permeate flux. The zeolite membrane achieved a good rejection of Na+ (~82%) for a NaCl feed solution with a TDS (total dissolved solids) of 3000 mg·L−1 at an applied pressure of 7 MPa and 21 °C. To explore the opportunity for high salinity and high temperature desalination, this membrane was also tested with high concentration NaCl solutions (up to TDS 90,000 mg·L−1) and at 90 °C. This is the first known work at such high salinities of NaCl. It was found that increasing the salinity of the feed solution decreased both Na+ rejection and flux. An increase in testing temperature resulted in an increase in permeate flux, but a decrease in ion rejection. Full article
(This article belongs to the Special Issue Membranes and Water Treatment)
Open AccessArticle Performance and Long Term Stability of Mesoporous Silica Membranes for Desalination
Membranes 2013, 3(3), 136-150; doi:10.3390/membranes3030136
Received: 17 June 2013 / Revised: 2 July 2013 / Accepted: 3 July 2013 / Published: 12 July 2013
Cited by 8 | PDF Full-text (1554 KB) | HTML Full-text | XML Full-text
Abstract
This work shows the preparation of silica membranes by a two-step sol-gel method using tetraethyl orthosilicate in ethanolic solution by employing nitric acid and ammonia as co-catalysts. The sols prepared in pH 6 resulted in the lowest concentration of silanol (Si–OH) species [...] Read more.
This work shows the preparation of silica membranes by a two-step sol-gel method using tetraethyl orthosilicate in ethanolic solution by employing nitric acid and ammonia as co-catalysts. The sols prepared in pH 6 resulted in the lowest concentration of silanol (Si–OH) species to improve hydrostability and the optimized conditions for film coating. The membrane was tested to desalinate 0.3–15 wt % synthetic sodium chloride (NaCl) solutions at a feed temperature of 22 °C followed by long term membrane performance of up to 250 h in 3.5 wt % NaCl solution. Results show that the water flux (and salt rejection) decrease with increasing salt concentration delivering an average value of 9.5 kg m2 h–1 (99.6%) and 1.55 kg m2 h–1 (89.2%) from 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 potable water. Long term stability shows that the membrane performance in water flux was stable for up to 150 h, and slightly reduced from thereon, possibly due to the blockage of large hydrated ions in the micropore constrictions of the silica matrix. However, the integrity of the silica matrix was not affected by the long term testing as excellent salt rejection of >99% was maintained for over 250 h. Full article
(This article belongs to the Special Issue Membranes and Water Treatment)
Figures

Open AccessArticle Successful Integration of Membrane Technologies in a Conventional Purification Process of Tannery Wastewater Streams
Membranes 2013, 3(3), 126-135; doi:10.3390/membranes3030126
Received: 11 April 2013 / Revised: 2 July 2013 / Accepted: 5 July 2013 / Published: 11 July 2013
Cited by 9 | PDF Full-text (213 KB) | HTML Full-text | XML Full-text
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, [...] Read more.
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 the overdesign of the membrane plant, as well as to define optimized operating conditions in order to handle fouling issues correctly for a 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 offered as an external service near tannery production sites, and, here, proposed to be substituted by membrane technologies. Full article
(This article belongs to the Special Issue Membranes and Water Treatment)
Open AccessArticle Strategic Co-Location in a Hybrid Process Involving Desalination and Pressure Retarded Osmosis (PRO)
Membranes 2013, 3(3), 98-125; doi:10.3390/membranes3030098
Received: 18 May 2013 / Revised: 24 June 2013 / Accepted: 24 June 2013 / Published: 4 July 2013
Cited by 15 | PDF Full-text (1142 KB) | HTML Full-text | XML Full-text
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 [...] Read more.
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 up to 23% in energy consumption is projected via the Hybrid Process. The attractiveness is amplified by potential capital cost savings ranging from 8.7%–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, 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. Full article
(This article belongs to the Special Issue Membranes and Water Treatment)
Open AccessArticle Separation Properties of Wastewater Containing O/W Emulsion Using Ceramic Microfiltration/Ultrafiltration (MF/UF) Membranes
Membranes 2013, 3(2), 87-97; doi:10.3390/membranes3020087
Received: 7 April 2013 / Revised: 6 June 2013 / Accepted: 10 June 2013 / Published: 21 June 2013
Cited by 1 | PDF Full-text (406 KB) | HTML Full-text | XML Full-text
Abstract
Washing systems using water soluble detergent are used in electrical and mechanical industries and the wastewater containing O/W emulsion are discharged from these systems. Membrane filtration has large potential for the efficient separation of O/W emulsion for reuses of treated water and [...] Read more.
Washing systems using water soluble detergent are used in electrical and mechanical industries and the wastewater containing O/W emulsion are discharged from these systems. 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 by cross-flow microfiltration and ultrafiltration were studied with ceramic MF and UF membranes. The effects of pore size; applied pressure; cross-flow velocity; and detergent concentration on rejection of O/W emulsion and flux were systematically studied. At the condition achieving complete separation of O/W emulsion the pressure-independent flux was observed and this flux behavior was explained by gel-polarization model. The O/W emulsion tended to permeate through the membrane at the conditions of larger pore size; higher emulsion concentration; and higher pressure. The O/W emulsion could permeate the membrane pore structure by destruction or deformation. These results imply the stability of O/W emulsion in the gel-layer formed on membrane surface play an important role in the separation properties. The O/W emulsion was concentrated by batch cross-flow concentration filtration and the flux decline during the concentration filtration was explained by the gel- polarization model. Full article
(This article belongs to the Special Issue Membranes and Water Treatment)
Open AccessArticle Experimental Study of Membrane Fouling during Crossflow Microfiltration of Yeast and Bacteria Suspensions: Towards an Analysis at the Microscopic Level
Membranes 2013, 3(2), 44-68; doi:10.3390/membranes3020044
Received: 7 February 2013 / Revised: 22 April 2013 / Accepted: 24 April 2013 / Published: 10 May 2013
Cited by 3 | PDF Full-text (3480 KB) | HTML Full-text | XML Full-text
Abstract
Microfiltration of model cell suspensions combining macroscopic and microscopic approaches was studied in order to better understand microbial membrane fouling mechanisms. The respective impact of Saccharomyces cerevisiae yeast and Escherichia coli bacteria on crossflow microfiltration performances was investigated using a multichannel ceramic [...] Read more.
Microfiltration of model cell suspensions combining macroscopic and microscopic approaches was studied in order to better understand microbial membrane fouling mechanisms. The respective impact of Saccharomyces cerevisiae yeast and Escherichia coli bacteria on crossflow microfiltration performances was investigated using a multichannel ceramic 0.2 µm membrane. Pure yeast suspensions (5 µm ovoid cells) and mixtures of yeast and bacteria (1 to 2.5 µm rod shape cells) were considered in order to analyse the effect of interaction between these two microorganisms on fouling reversibility. The resistances varied significantly with the concentration and characteristics of the microorganisms. Membrane fouling with pure yeast suspension was mainly reversible. For yeast and bacteria mixed suspensions (6 g L−1 yeast concentration) the increase in bacteria from 0.15 to 0.30 g L−1 increased the percentage of normalized reversible resistance. At 10 g L−1 yeast concentration, the addition of bacteria tends to increase the percentage of normalized irreversible resistance. For the objective of performing local analysis of fouling, an original filtration chamber allowing direct in situ observation of the cake by confocal laser scanning microscopy (CLSM) was designed, developed and validated. This device will be used in future studies to characterize cake structure at the microscopic scale. Full article
(This article belongs to the Special Issue Membranes and Water Treatment)

Review

Jump to: Research

Open AccessReview Advancement in Electrospun Nanofibrous Membranes Modification and Their Application in Water Treatment
Membranes 2013, 3(4), 266-284; doi:10.3390/membranes3040266
Received: 3 September 2013 / Accepted: 13 September 2013 / Published: 30 September 2013
Cited by 12 | PDF Full-text (949 KB) | HTML Full-text | XML Full-text
Abstract
Water, among the most valuable natural resources available on earth, is under serious threat as a result of undesirable human activities: for example, marine dumping, atmospheric deposition, domestic, industrial and agricultural practices. Optimizing current methodologies and developing new and effective techniques to [...] Read more.
Water, among the most valuable natural resources available on earth, is under serious threat as a result of undesirable human activities: for example, marine dumping, atmospheric deposition, domestic, industrial and agricultural practices. Optimizing current methodologies and developing new and effective techniques to remove contaminants from water is the current focus of interest, in order to renew the available water resources. Materials like nanoparticles, polymers, and simple organic compounds, inorganic clay materials in the form of thin film, membrane or powder have been employed for water treatment. Among these materials, membrane technology plays a vital role in removal of contaminants due to its easy handling and high efficiency. Though many materials are under investigation, nanofibers driven membrane are more valuable and reliable. Synthetic methodologies applied over the modification of membrane and its applications in water treatment have been reviewed in this article. Full article
(This article belongs to the Special Issue Membranes and Water Treatment)
Open AccessReview Pretreatment and Membrane Hydrophilic Modification to Reduce Membrane Fouling
Membranes 2013, 3(3), 226-241; doi:10.3390/membranes3030226
Received: 20 June 2013 / Revised: 27 August 2013 / Accepted: 27 August 2013 / Published: 4 September 2013
Cited by 10 | PDF Full-text (247 KB) | HTML Full-text | XML Full-text
Abstract
The application of low pressure membranes (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 summarizes the two factors causing the organic [...] Read more.
The application of low pressure membranes (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 summarizes the two factors causing the organic membrane fouling, including molecular weight (MW) and hydrophilicity/hydrophobicity of NOM, and then presents a brief introduction of the methods which can prevent membrane fouling such as pretreatment of the feed water (e.g., coagulation, adsorption, and pre-oxidation) and membrane hydrophilic modification (e.g., plasma modification, irradiation grafting modification, surface coating modification, blend modification, etc.). Perspectives of further research are also discussed. Full article
(This article belongs to the Special Issue Membranes and Water Treatment)

Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

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