Water. desalination + reuse

RESEARCH | 34 | Desalination & Water Reuse | November-December 2014 Filmtec Seamaxx and Filmtec elements against values from using its own Reverse Osmosis System Analysis (ROSA) simulation software. The total dissolved solids (TDS) values projected by ROSA for the permeate water quality were very close to those indicated by actual associated conductivity levels found in the trial (figure 8). This finding, says Salgado, confirmed the suitability of ROSA as a sound basis for estimating performances of a RO system including Filmtec Seamaxx elements. CommERCiAl-SCAlE tESting Dow had demonstrated earlier the value of full-scale testing of Filmtec Seamaxx at an installation in the Canary Islands in the Atlantic Ocean. The plant had been in operation for eleven years producing drinking-quality permeate water and required an overhaul to achieve three objectives: to increase the capacity of the plant; to reduce the energy consumed in the desalination process; and to maintain the purity of the permeate water – while complying with local and international permeate water quality regulations. For the overhaul, the RO membrane configuration included a hybrid set up with two types of elements: Filmtec SW30XHR- 440i in the first three front positions of the pressure vessel and Filmtec Seamaxx elements in the four rear positions. In this commercial-scale study, the performance of the desalination plant was compared with the performance of the previous elements as well as with the predicted or expected performance of Filmtec Seamaxx according to ROSA and Dow's FT- Norm normalization software. Rejection of dissolved salts, particularly those containing boron, was monitored by analysis in Dow's research and development facilities and in external certified laboratories. In addition to the change of RO elements, Danfoss's exchange pressure system, I-Save 40, and its APP-24 high-pressure pump replaced the existing high-pressure pump which included a frequency converter and Pelton turbine. The revamp was completed at the start of 2013. After almost one year in operation, performance of the Filmtec Seamaxx element has been validated through different seasons and different sets of operating conditions, confirming the expected savings in energy consumption. Despite a 37.5% increase in permeate flow rate to 550 m 3 /h, energy consumption was reduced by 58% to 4.9 kWh/m 3 with the Filmtec Seamaxx/ Filmtec combination (table 3). Figure 3. Feed pressure difference remained steady throughout the trial. Figure 4. The difference in permeate flow was negligible. Figure 5. The high-pressure parallel arrangement for the fouling study.

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