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Membrane technology is a general term used to describe a number of filtration processes. The processes are essentially the same with the difference being in the membrane that is used. This membrane separation process is based on semi-permeable membranes. The principle of this method is that the membrane acts like a filter, allowing water to pass through while solids and other substances are held back. Membranes act as a selective separation wall.
Membrane filtration can be categorized as microfiltration (MF) and ultrafiltration (UF) on one end, and nanofiltration (NF) and reverse osmosis (RO) on the other end. MF and UF are used when there is a requirement to remove larger particles such as macromolecules and molecules. There is a low-pressure difference in the above case. NF and RO are used when salts and minute particles to the level of ions are required to be removed. Due to the size of the minute particles, the pressure required is much higher than that of MF and UF.
Membrane filtration can be used as an alternative to flocculation, sediment purification techniques, sand and carbon filters, extraction and distillation. Membranes also can be used in application areas such as chemicals and pharmaceutical processing, energy and environmental applications, industrial processing, and food and beverage manufacturing units.
Membrane technology has gained popularity and acceptance in the past few decades. This is due to the fact that membrane technology works without the addition of chemicals, requires relatively less energy and adopts well-arranged process conductions.
Need for technologies
Rising concern for the quality of water obtained after the treatment of water and wastewater is one of the major reasons for the adoption of membrane technology. This is because membrane technologies remove contaminants to the lowest level possible. Growing populations and the scarcity of water near densely populated cities are additional reasons for the adoption of these technologies.
Another incentive to use membrane technology is that it involves fewer chemicals during the treatment of water and wastewater, so treatment does not generate toxic end products. Stringent regulations set by the U.S. EPA and the Urban Wastewater Treatment Directive and Integrated Pollution Prevention and Control (IPPC) in Europe are also motivating factors for membrane technologies.
Top industry challenges
Though membrane technologies are widely accepted and popular, they still face a few challenges that need to be addressed. Some of the technology challenges are issues related to membrane fouling; membranes need to successfully handle the complexities of wastewater streams, especially in the industrial sectors and in the effective leveraging of recycling and reusing concepts after membrane filtration.
Issues hampering the growth of the membrane technology industry include the price of these membranes, along with the operating and maintenance costs. Industries and municipalities have yet to fully embrace membrane technologies, and the robustness and life span of these membranes still fall short with respect to market demands.
Membrane technologies have advanced at a rapid pace in the last decade, both on the technology and market sides. Research is being conducted on the technology side at the university level and at the industry level.
One of the noteworthy findings at the university level is the development of microporous membranes made from polypropylene by researchers at the University of Chile. This membrane finds its applications especially in MF for the removal of bacteria and viruses, the clarification of beer or wine, the treatment of wastewater, oil/water separation, oxygenation, and as base material for affinity separation.
Researchers at Northwestern University have introduced a novel mathematical tool that helps in ascertaining the extent of rejection of organic solids onto a membrane. This helps in the designing of RO and NF membranes.
New York-based ITT Industries developed a dual-stage membrane reactor that combines the biological filtration and membrane filtration stages into one unit, which helps reduce cost.
Certification of the Homespring system developed by Zenon Environmental, Inc. (now Zenon Membrane Solutions, a part of GE Water & Process Technologies) is another important landmark with respect to domestic water treatment. This is helpful in the direct purification of water from lakes and other water bodies for use in country homes and cottages. It combines both pretreatment and filtration in one step, which is a rare phenomenon.
On the market side, a recent Frost & Sullivan study—U.S. Ultrafiltration, Nanofiltration and Reverse Osmosis Membrane Elements—estimates the revenues for the total UF, NF and RO membrane elements market to be around $385 million in 2006, with a revenue growth rate of 6.4% from previous years. It is predicted that in 2010, the revenues for the same market are expected to be approximately $520 million, with a revenue growth rate of 8.6%.
Membrane technologies are not uniformly spread across one industry. They are scattered in various sockets that are spread across industries such as chemical, pharmaceutical, and food and beverage. The future for membrane technologies lies in the adoption of strategies so that they create the right kind of impact in a uniform manner across the industry.
Membrane need and adoption varies from industry to industry and in some cases, from region to region. Hence, it is essential to identify the key areas on which to concentrate so that membranes cater to every tier in the industry.
Some of these key areas are discussed below: