Water. Desalination + reuse
Issue link: https://fhpublishing.uberflip.com/i/513849
looking at it from a feed water perspective and it continues to grow. "It is an area where Dow is investing and innovating because it is important today and for the future of the business. And one of the strongest trends is in the energy reduction membrane market," he says. Dow's energy-saving Filmtec Eco RO came about, the company says, through a combination of a breakthrough in the chemistry of the polyamide membrane and upgrades in the feed spacer which brought about lowered energy consumption and reduced the use of chemicals. The Filmtec Eco product won the 2013 Innovation Award at Aquatech China. More recently Dow's Filmtec Eco membrane technology won a prestigious Edison Award for its innovation and contribution to combat global water scarcity. Which sectors form the pockets of greatest demand for energy effcient desalination? "A number of segments of the industrial water sector care about quality as much as effciency," says Pinto. He points to food and beverage producers, the pulp paper industry, and the petrochemical industry. "We are making progress in these areas," he says. In the past year US government incentives have emerged to bring on wastewater reuse and recycling as water scarcity has gripped the west coast and south with California and Texas the most notably blighted. But the commercial impact of the political drive is, according to Pinto, yet to make a signifcant mark. "The wastewater trend in the US at the business level? It's too early to talk about it. The absolute number is not as great as the noise being generated around it but I'm pretty confdent it will emerge in the future," says Pinto. "There is a strong low-energy market in Europe despite the economic headwinds. And the brackish water space correlates with economic growth so there is growth in the emerging economies notably China and India," he adds. The bulk of the energy effciency business is in retroft and replacement says Pinto but he adds: "There is a good amount of new installations". And what of future challenges in the energy effciency arena? "The overview is about producing high levels of purity at lowest cost – capex and opex. These are the drivers for innovation," says Pinto. Dow claims that the operational cost savings, available in replacing conventional RO membranes with Eco, amount some 16-19%. Those cost reductions, Dow PROJECTS Powerful stuff In a beverage industry application for Filmtec Eco, a large US brewery treated brackish water supplies not for the beer production but for the power plant providing electricity for the site. Dow worked with the system provider for the plant, Consolidated Water Solutions. The plant had operated previously for seven years with a two-pass RO system. Consolidated and Dow worked with the power plant company to reduce the energy required to treat boiler feed make-up water used in the brewery's electricity production and process steam requirements. The treatment of boiler feed water is critical, because use of untreated water in the quite extreme pressures and temperatures involved can lead to lower effciency and possible damage as well as a need for frequent cleaning. Since 95% of water used in boiler operation can be reused it is vital that the feed water and recycled condensate are treated to prevent scale and corrosion in the steam water circuit. The brewery power plant source water was a highly variable and seasonally tempered combination of mountain and snow run-off. So the plant required a treatment technology that functioned across various temperatures and pressures. Since incorporating Filmtec Eco RO elements the optimal operating pressure for the pressure vessel reduced to 50-60 psi reducing its energy demand by 10-20% says Dow. The winter months brought colder source water at 7°C requiring the system to operate at a higher pressure, which requires more energy. Filmtec Eco elements were able to handle high feed water rates, and hit peak water fow rates in winter which, according to Pinto, was a major challenge under the previous regime. As well as reducing pipe pressure Filmtec Eco reduced the impact of fouling in the RO system, through its outstanding cleaning effciency says Pinto. The cost of cleaning, downtime and lost system performance can be signifcant, so reduced fouling was key to reducing costs while providing reliable power to the brewery for operations. "We often talk about the energy savings but for a large production plant like this, downtime is critical," says Pinto. President of Consolidated, Duane Miller, said: "Filmtec Eco technology has helped our power customer obtain cost savings, which we did not fnd in other top industry-grade membranes." A highly demanding source water was the challenge at a power plant in Alberta, Canada where Dow introduced an innovative two-pass RO design to reduce the plant's energy demand for the second pass and stem fouling at the front end. The design includes Eco RO elements and another Filmtec RO product, XFRLE-400/34i elements. The Filmtec Eco elements reduced energy demand in the system's second pass by 30% and the XFRLE membranes in the frst pass improved overall pressure drops and fouling. The lake source water at the power station was itself derived from a combination of the North Saskatchewan river; mine drainage; plant site drainage; sewage effuent; and chemical neutralization ponds. This variable source water called for thicker feed spacer elements to reduce fouling rates, and to lower the pressure drop in the frst pass. The two low-energy elements were equipped with low pressure-drop feed spacers to reduce operating pressures, and so reduce operating costs. They also countered the effects of the cool feed water temperature which is at 7-26°C. The Eco elements have reduced chemical usage enabling the operators not to remove carbon dioxide with caustic in the second pass, while maintaining high permeate quality for continuous electrodeionization polishing prior to feeding the boiler. A rocky supply May-June 2015 | Desalination & Water Reuse | 21 |