Water. desalination + reuse

| 32 | Desalination & Water Reuse | November-December 2014 RESEARCH _________ Trevor Loveday, editor, D&WR ___ Editor's note: while product development is a commercial must the payback on investment in testing is possibly less clear. Dow explains how it sees a smoother path to market with the confidence gained from testing in its home-spun, real-world test centre. REDUCING THE the energy consumed in the production of each cubic metre of pure water by seawater desalination has long been the highest priority for developers of reverse osmosis (RO) membranes. The imperative has stepped up in recent years, fuelled by increasing energy costs and a need to rein in thermal power production in the face of climate change. Dow Water and Process Solutions has continued to up the performance of its Filmtec RO element product line for nearly 30 years since its first launch. Each development improved on the previous design in addressing the perennial issue of energy – and therefore cost – reduction. They have responded also to market changes. The latest Filmtec Seamaxx RO element, and a number of steps in the pathway to it, have brought significant improvements in permeate flow to improve the economics of RO in the face of escalating demand. Those gains have been accompanied by a small sacrifice in dissolved solids rejection (figure 1). The increased recovery made possible by the high permeability of Filmtec Seamaxx elements gives RO plant developers greater choice says Dow. Operators can opt to keep to their existing recoveries but with smaller plant and consequently reduced capital outlay. Or they can maintain plant size and work at pressures comparable to, or even lower than, typical feed pressures to reduce operating energy costs relative to costs associated with other seawater membranes. "Filmtec Seamaxx was launched in 2013 providing high permeability to seawater for the market in new installations where they want to go for lower energy costs. When a plant is revamped it is usually to replace existing products that have high-energy requirements. So we made the Filmtec Seamaxx product move," says Dow technical specialist, Blanca Salgado. But she emphasizes the importance of investment in testing that matches real-world challenges to verify product performance: "To get support for Filmtec Seamaxx elements we need to gain trust therefore we have very long-term trials," she says. In 2011 Dow set up its Global Water Technology Centre test facility at Tarragona, on the east coast of Spain to equip itself to carry out large-scale, long- term testing. Salgado says the facility is "unique" in its approach to producing test conditions and data that align with commercial operation: "Units run exactly as in industry – during months or years without interruption – using seawater. "Many publications very often present results from one or two weeks' continuous operation and from small pilots that are not comparable to large-scale operations," she says. Salgado and a team of collaborators from Veolia Water Technologies, and Spain's Universitat Rovira i Virgili, recently presented findings from Filmtec Seamaxx element testing at Tarragona and at an external site. Those tests comprised two pilot operations; one to show the product's long-term performance and another to demonstrate fouling resistance. A third study was conducted in a fully operational plant elsewhere in Spain. Long-Term evaLuaTion During an eight-month trial, Filmtec Seamaxx RO elements were compared with a well-established Dow product, Filmtec SW30XLE-4040. The two elements were operated in parallel at the same production level and flux to scrutinize energy savings from the use of Filmtec Seamaxx along with fouling trends over the test period (figure 2). Seawater from the Mediterranean was passed through The real value of commercial-scale testing

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