Water. Desalination + reuse
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Water. desalination + reuse June 2018 Tech Quarterly 25 mode, and it will show you the highest recovery you can get, relevant to the water chemistry and hydraulics," says Malki. Hydraulic challenge The reason why AWC wanted to model the Desalitech system has to do with hydraulics. A conventional system running at 90 per cent recovery might com- prise three stages, each with seven membrane elements. In such a system, the required feed pressure would be so high that the rst-in-line elements would desalinate the majority of the water, and the nal elements would run dry. "The biggest problem was when the feed water has total dissolved solids (TDS) of several thousand parts per million. Then, even using boost pressures and permeate back-pressure adjustments, it didn't work hydraulically with a six or seven element-long system," says Malki. "Of course, one could build a system with booster pumps every four ele- ments, but that adds capital cost and would take up a large footprint." By comparison, the CCRO has a single stage of ve or six elements, and the feed pump increases its pressure with every cycle as the osmotic pressure increases. "This means that you can never run into hydraulics issues where the pressure required in the tail element causes the feed elements to make too much water. These scenarios are a great t for Desalitech," Malki adds. Chemistry benefi t In modelling the CCRO, one big diŠ erence in the water chem- istry between a closed-circuit and a conventional RO system that emerged was pH, with implications for membrane scaling. "In a conventional RO, the pH rises between the feed and the concentrate, and the concentrate pH is always signi cantly higher than the feed pH. If you're running at 90 per cent recovery, and your feed pH is 8, the concentrate pH may be 8.8 or 8.9. With CCRO, 100 per cent of the concentrate is blending back into the feed water. Concentrate makes up half of the water re-entering the membranes with every cycle, therefore the concentrate pH is getting pulled back down so overall, the concentrate pH that aŠ ects scaling ends up being signi cantly lower. The CCRO has a chemistry bene t that helps to reduce the scaling," explains Malki. "As well, when the concentration gets very high it gets purged, and exits over a short period — there are lots of types of scaling that are slow to form, they may take several minutes, and the CCRO ' ushes the water containing the forming scales before the crystals can embed into the membranes." System comparison The application of Proton so" ware can be at the start of a project as part of understand- ing aspects of its feasibility, or to help optimise or replace an existing treatment system. In one example, a pulp and paper manufacturer that wanted to double its production of paper was barred by the local munici- pality from increasing its dis- charge to the sewer system. The company was therefore driven to innovate and to nd ways to produce more water for use in the paper-making process without increasing its volume of wastewater. "The customer lighted upon Desalitech, and in that instance could go to Proton, input its existing water chemistry and conventional RO system design, and con rm 'yes, we are currently seeing that recovery,' and then switch to the Desalitech CCRO mode and evaluate on that same water quality," explains Matt Jones, Desalitech regional director. "In that particular case they were able to go from a 75 per cent recovery rate with a traditional RO system, to 92 per cent recovery with the CCRO." Jones adds: "The best thing is that it's a one-stop-shop so" ware where you run the anti-scaling projections, model various designs, compare traditional RO with CCRO. That comparison is powerful for designers and engineers out there who want to see truly the diŠ erences between the two processes, from a chemistry and hydraulics perspective, and to compare diŠ erent membranes. You can do it all in one place in real-time, change pH and temperature, and see the eŠ ect on recovery." Tech news in brief Suez WTS introduces new app for ZeeWeed membranes Suez Water Technologies & Solutions has introduced a new app to simplify data collection and record keeping for ZeeWeed membrane trains, cassettes and modules. The mobile app, ModuleTrac, enables water plant operators to track, monitor and analyse the membranes, providing enhanced visibility of the module, cassette and train data on the company's InSight platform. The app uses a unique bar code on each module to scan and track its location and maintenance history. The data is fed into InSight for analysis, archiving and reporting, and customers can view data, run reports, and create graphs and charts to monitor and optimise their water treatment systems. The app is available for iOS and Android, and has an offl ine mode to capture data where there is no internet connection. Veolia presents new digital platform Aquavista Veolia Water Technologies has launched a new suite of digital technologies dedicated to water treatment applications. The platform features 350 applications covering its full range of water treatment technologies and systems, including desalination and reuse. The various digital- based services can be bundled and adapted to fi t specifi c needs. They include diagnostics, real-time troubleshooting services, water quality monitoring, predictive maintenance, and compliance services, and are aimed at improving asset performance, and reducing energy and chemical consumption. The platform is intended for plant owners and operators at municipalities and industrial clients, to help them to manage their water treatment systems. Data and insight platforms for desalination systems are evolving to support improved performance