Membrane Technology For Water Treatment Research Articles

First UK-Israeli Workshop on the Application of Membrane Technology in Water Treatment and Desalination and 2nd Oxford Water and Membranes Research Event 15th–20th June 2008

The sustainable treatment and supply of potable water and the disposal of wastewater are among the major challenges of the 21st century, and of rapidly growing national and international significance. Membrane technology in water treatment is establishing itself as one of the most promising future solutions for the high quality, sustainable treatment of both potable and wastewater at reasonable price. A consortium of leading UK and Israeli scientists convened at the University of Oxford from June 15th to 20th, June 2008 to participate in a Joint UK-Israeli Workshop and Research Conference on the Application of Membrane Technology in Water Treatment and Desalination. The event was the first of its kind, and fell within the remit of the Israeli Science Networking Development Scheme (SNDS) in the area of Natural and Engineering Sciences. It concerned a topic to which both the UK and Israeli governments have attached a present and future priority. Funds were provided by the SNDS to allow six delegates from each country to participate in the event, which consisted of a 2-day intensive workshop followed by a 2.5-day conference open to a wider audience of around 40 delegates. The event was a huge success, resulting in a basis for both future collaborations between Israeli and British scientists, and for future student and faculty exchanges. With the kind support of Miriam Balaban, selected papers from the event are now being published in the Desalination and Water Treatment Journal. As with the previous Water and Membranes Research Event at Oxford, it turned out to be a most stimulating and unique experience, in a special intellectual, architectural and social environment. Once again, the participants learned much from their colleagues, engaging actively in the research discussions, as well as finding new friends and fresh inspiration. In the spirit of the event, plenty of time was also built in for informal discussions and social interaction. We hope you find the papers of interest, and look forward very much to seeing some of you at the next Oxford event. Desalination and Water Treatment 8 (2009) 1

Preparation and characterization of alumina hollow fiber membranes

With the rapid development of membrane technology in water treatment, there is a growing demand for membrane products with high performance. The inorganic hollow fiber membranes are of great interest due to their high resistance to abrasion, chemical/thermal degradation, and higher surface area/volume ratio therefore they can be utilized in the fields of water treatment. In this study, the alumina (Al2O3) hollow fiber membranes were prepared by a combined phase-inversion and sintering method. The organic binder solution (dope) containing suspended Al2O3 powders was spun to a hollow fiber precursor, which was then sintered at elevated temperatures in order to obtain the Al2O3 hollow fiber membrane. The dope solution consisted of polyethersulfone (PES), Nmethyl-2-pyrrolidone (NMP) and polyvinylpyrrolidone (PVP), which were used as polymer binder, solvent and additive, respectively. The prepared Al2O3 hollow fiber membranes were characterized by a scanning electron microscope (SEM) and thermal gravimetric analysis (TG). The effects of the sintering temperature and Al2O3/PES ratios on the morphological structure, pure water flux, pore size and porosity of the membranes were also investigated extensively. The results showed that the pure water flux, maximum pore size and porosity of the prepared membranes decreased with the increase in Al2O3/PES ratios and sintering temperature. When the Al2O3/PES ratio reached 9, the pure water flux and maximum pore size were at 2547 L/m2·h and 1.4 μm, respectively. Under 1600dgC of sintering temperature, the pure water flux and maximum pore size reached 2398 L/(m2·h) and 2.3 μm, respectively. The results showed that the alumina hollow fiber membranes we prepared were suitable for the microfiltration process. The morphology investigation also revealed that the prepared Al2O3 hollow fiber membrane retained its’asymmetric structure even after the sintering process.

Membrane technologies for water treatment and agroindustrial sectors

Abstract Although water is essential for human survival and progress, it is distributed very unevenly and with a different purity over the surface of the earth. A variety of contaminants can be present in raw water, depending on its origin. The size of these contaminants ranges from the micrometer (e.g. bacteria) to the tenths of a nanometer order (ions). Membrane processes like microfiltration, ultrafiltration, nanofiltration and reverse osmosis could be a solution for an advanced physical treatment of water for drinking purposes as well as for agroindustrial sectors. Many applications are well assessed and are expanding very quickly; however, to obtain an ever-growing performance, it is necessary to prepare membranes with tailored structure and transport properties. Characterisation methods play also a role of paramount importance for the selection of the more appropriate membrane for the above-mentioned applications. In this work the main membrane preparation techniques and characterisation methods will be reviewed and discussed.

Development of membrane testing protocols for characterisation of RO and NF membranes

The CSIRO Flagship Cluster project Advanced Membrane Technologies for Water Treatment is a collaboration of nine Australian Universities and the CSIRO looking at improving the energy efficiency of desalination of seawater using membrane processes. One of the initial aims of the cluster is to develop a standardised suite of tools and techniques for the characterisation of membranes for seawater desalination. Measures used to assess membrane separations are speed, selectivity and stability. These three performance measures depend upon the physical and chemical properties of the membrane, the feedwater and the type of filtration process being used (i.e. Dead end batch filtration versus continuous crossflow filtration). Our proposed testing protocol will cover three main categories; transport properties, pore characteristics and surface properties. The transport properties of membranes are strongly related to the pore and surface characteristics, however no general predictive capability exists yet that is widely accepted in the literature.

Irreversible Fouling in MF/UF Membranes Caused by Natural Organic Matters (NOMs) Isolated from Different Origins

For more efficient use of membrane technology in water treatment, it is essential to understand more about the fouling that requires chemical cleaning to be eliminated (i.e., irreversible fouling). In this study, five different MF/UF membranes and four types of organic matter collected from different origins were examined in terms of the degree of irreversible membrane fouling. Experimental results demonstrated that the extent of irreversible fouling differed significantly depending on the properties of both the membrane and organic matter. Among the tested membranes, UF membranes made of polyacrylonitrile (PAN) exhibited the best performance in terms of prevention of irreversible fouling. In contrast, MF membranes, especially one made of polyvinylidenefluoride (PVDF), suffered significant irreversible fouling. Conventional methods for characterization of organic matter such as specific ultraviolet absorption (SUVA), XAD fractionation, and excitation‐emission matrix (EEM) were found to be inadequate for prediction of the degree of irreversible fouling. This is because these analytical methods represent an average property of bulk organic matter, while the fouling was actually caused by some specific fractions. It was revealed that hydrophilic fraction of the organic matter was responsible for the irreversible fouling regardless of the type of membranes or organic matter.

Application of membrane technology for water treatment: Ultrasound-associated cleaning of fouled microfiltration membranes

Lead (Pb) is normally considered as a trace element in soils and sediments for geochemical study. However, the concentration of Pb in firing range soils is generally so high that it should be considered as a major element during the evaluation of the soil geochemical properties. Soil organic matter (SOM) has been reported as one of the major factors to expedite the corrosion of metallic lead (Pb) in acidic and organic-rich soils. The main impacts of SOM on the fate and transport of Pb in firing range soils lie in the following two aspects; (1) the complexation of organic matter with Pb, which has received lots of attention, and; (2) changes in soil redox potential due to the transformation of SOM and its subsequent impact on Pb speciation, which has rarely been investigated. Soils from 6 different f a n g ranges are selected for this study. These samples have been stored under a closed condition for more than 3 years. The soil moisture contents were well-retained, as all the samples were kept in closed plastic buckets. The analytical data showed that the summation of the soil total organic carbon content (TOC) and inorganic carbon contents (TIC) were consistent with soil total carbon contents (TC) measured in previous years, although the TOC and TIC contents have changed respectively after years of storage. In general, it is observed that the soil TOC decreased against an increase of TIC. The mass balance on such a transformation suggested a major conversion of organic carbon (Corg) to inorganic carbon (CO32) in the stored soils. This kind of conversion could result in a significant change in soil redox potential (oxidation), which favoured Pb carbonation. At least, the presence of SOM could greatly affect the Pb weathering process (carbonation) in f~ing range soils under anaerobic conditions.

Integrating photocatalysis and membrane technologies for water treatment.

Removal of organic contaminants in water may sometimes be more easily achieved with a pair rather than with a single unit operation. We explore here the combination of an ambient temperature, chemical oxidation photocatalysis (PC) process with physical separation via a membrane operation, microfiltration (MF), ultrafiltration (UF), or reverse osmosis (RO) using both a conceptual statement and a literature review format. Four configurations are noted and discussed here: (1) PC + MF for catalyst slurry recycle, (2) PC + UF for catalyst slurry and (polymer) reactant recycle, (3) immobilized PC and UF/RO for reactant recycle, and (4) immobilized PC on UF/RO membrane for membrane self-cleaning. Although the literature review is encouraging with respect to plausibility, the paucity of examples indicates a need for substantial effort to fully exploit the suggested possibilities for process development.

Developments in membrane technology for water treatment

Membrane technology is widely accepted as a means of producing various qualities of water from surface water, well water, brackish water and seawater. Membrane technology is also used in industrial processes and in industrial wastewater treatment, and lately membrane technology has moved into the area of treating secondary and tertiary municipal wastewater and oil field produced water. In many cases one membrane process is followed by another with the purpose of producing water of increasing purity and quality for various purposes. One type of membrane may thus enhance the function of another to meet goals ranging from disposal of wastewater to production of drinking water from unexpected sources. In this way membrane technology offers the possibility of managing the total water resources in a region, which is of special interest in geographical areas where the natural water resources are scarce. The spiral wound membrane element configuration is the most widely used due to its high packing density and relatively low price. This paper will describe some technological advance in the area of innovative new membranes and application concepts for spiral wound membrane elements. Spiral wound elements span the four commonly defined membrane technologies, which are microfiltration (0.01-0 microns), ultrafiltration (500–100,000 Da), nanofiltration (100–500 Da), and reverse osmosis (up to 100 Da). A sandwich consisting of two membrane sheets with an inserted permeate carrier is glued together and to complete the membrane package a feed spacer is inserted between the opposing membrane surfaces. The membrane package is wound around a perforated central tube through which the permeate exits the element. The physical shape of a membrane element is secured by applying a suitable outer wrap. The physical and chemical properties of the various materials, including the membrane, are chosen according to the operating parameters. The typical reverse osmosis elements have limitations with respect to temperature (45°C), pH value (2–10), silt density index (less than 3 SDI), chlorine (dechlorination mandatory) and several other parameters. This is acceptable for conventional pure water applications, but for more complex membrane applications these limitations must be diminished or removed. Advanced materials and material science have been applied to the membranes, materials and construction of spiral wound elements. This effort has resulted in elements with improved operating parameters and wider areas of applications. A host of new membrane applications have been made possible and there is no limit in sight, except that new applications must rest on a profitable foundation for the user. Scarcity of water, environmental requirements and the simple logic of reusing water instead of discharging it are conditions, which call for increased use of membrane technology in a multitude of applications.

The Use of Membranes for Salt Reduction in the UK

ABSTRACTReverse‐osmosis membranes, which have been used for reducing the salt content of water since the late 1960s, are available for a variety of desalination applications, ranging from seawater to brackish water and specific species removal, including hardness and organics. In recent years, major advancements have been made in the salt‐rejection capabilities and in pressure requirements, which have made the use of membrane technology in water treatment an attractive proposition.The paper focuses on (i) seawater desalination, reviewing the present study which is being carried out by Anglian Water; (ii) brackish water desalination, in particular a project which is being undertaken by Essex and Suffolk Water, and (iii) well‐water desalination, describing a project which is being executed by Anglian Water.

Membrane technology for water treatment

Lee F Comb, Director of Engineered Products & System at Osmonics Inc, explains here how the use of reverse osmosis, manofiltration and ultrafiltration membranes it to the advantage of water treatment plants.