Water. desalination + reuse

RESEARCH | 30 | Desalination & Water Reuse | February-March 2014 other depending on external factors such as feedwater quality, operating conditions, pretreatment systems used and chemistry. So, to be truly effective, a cleaning programme needs to incorporate multiple mechanisms. The new combination of Genesol 704 with air definitely ticked this box. The system, which soon took on the name Genairclean, incorporates: • Detergent, surfactant and chelants – these interact with foulants, facilitating removal • Normal osmosis – movement of permeate helps to dislodge foulant deposits • Effervescence – microbubbles produce turbulence, agitating and lifting the deposits. MEMbRAnE CoMpAtibility tESting From initial lab tests, the team was confident that Genairclean would work effectively to maximise and speed up foulant removal at RO plants with challenging feed waters. However, they first needed to ensure that the process would cause no damage to membranes. To test this, the researchers began by applying Genesol 704 and microbubbles to virgin membrane coupons for extended periods of time. These were then sent to colleagues in Spain for analysis. Scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDAX) and infrared (IR) work confirmed that there was no damage to the polyamide layer or change to the original salt rejection or flux capabilities. The exercise was then repeated with new full size 8-in RO membranes from Dow Filmtec, Hydranautics, Koch and Toray, using the new pilot plant. Following repeated exposure to the Genairclean method, samples of the membranes were tested for the presence of damage or changes to the flux or salt-rejection performance. Again IR and SEM-EDAX analysis proved that continual use of the method had no negative effects on the membranes. pilot tESting on foulEd MEMbRAnES Genesys then began testing on fouled membranes taken from different operational plants in the UK and the Middle East with a proven history of biological and organic fouling. To verify the superior effectiveness of the Genairclean technique, tests used a variety of combinations and compared the impact on foulant removal. These included applying: • Genesol 704 with and without microbubbles • Other Genesol cleaning chemicals with and without microbubbles • Commodity chemicals, with and without microbubbles. As predicted, Genesol 704 combined with air proved to be considerably more efficient at removing foulants than all the other combinations tested. Membrane flux increased by an average of 50% using this technique, compared with 30% Chemical and physical generation reduce bubble size to 5-500µm increasing agitation at the membrane surface Early laboratory experiments showed that bubble size decreased and distribution increased on addition of Genesol 704

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