Water. desalination + reuse

DWR MayJune 2016

Water. Desalination + reuse

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| 18 | Desalination & Water Reuse | May-June 2016 TECHNOLOGY The world is running ouT of water. By 2025 nearly 1 billion people will lack access to fresh, drinkable water. Reverse Osmosis (RO) water treatment will play a major role in alleviating water scarcity, however, this desalination technique is energy intensive. Any improvement of the membrane or element technology that can increase the energy efficiency of the RO process will be important. In a co-research project, Conwed Plastics and LANXESS' Liquid Purification Technologies business unit have proven that innovations in feed spacer technology lead toward enhanced RO element performance. The Reverse Osmosis process Reverse Osmosis is a water purification technology to remove mainly monovalent ions (e.g. NaCl) that utilizes a semipermeable membrane. An applied pressure is used to overcome natural osmotic pressure. Such RO membranes are being offered as spiral wound elements for a huge variety of desalination applications. Frequently known as scrim, mesh, net, or netting, feed spacers act as one of the layers of spiral wound RO elements and provide vital separation between the membranes to achieve superior filter performance. A spiral wound element refers to a membrane configuration which is comprised of "flat sheet membrane - permeate channel spacer - flat sheet membrane - feed channel spacer" combinations rolled up around a permeate collection tube. As shown on Figure 1, the membrane element structure contains the feed spacer that separates the surfaces of adjacent membrane envelopes. The feed spacer, configured as a net, keeps the feed channel open, allowing feed water to flow inside the feed channels, along the membrane element; RO challenges There are many challenges within the RO membrane water treatment process. With respect to feed spacers as a component in the overall RO element design, the critical issues are: Innovations in feed spacer technology can enhance the performance of reverse osmosis technologies, say Conwed Plastics and LANXESS _________ Dr Carsten Schellenberg and Alan D. Sharpe ___ Innovative feed spacer technology leads to enhanced reverse osmosis element performance Feed Water Brine Seal Cen re Pipe Permeate Feed Water Permeate Permeate Spacer (Tricot) Feed Spacer (Netting) RO Membrane Concentrate Water Figure 1

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