Water. desalination + reuse

DWR FebMarch 2015

Water. Desalination + reuse

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TECHNOLOGY | 28 | Desalination & Water Reuse | February-March 2015 FOLLOWING A three-year research project investigating new methods of cleaning membranes used in reverse osmosis, nanofi ltration, and ultrafi ltration the Genesys research team discovered a combination of cleaning mechanisms that was effective in removing obstructive deposits including clay and biofi lm. The combination is one of a stream of pulsing microbubbles in an off-line cleaning solution using a specially formulated cleaning compound. The high ionic strength of the cleaning solution causes a low fl ow of permeate water through normal osmosis during a soaking period when there is no fl ow or pressure on the feed side of the membrane. This disrupts and lifts deposits. The introduction of microbubbles with diameters of 5-500µm agitates deposits around the feed spacer to step up deposit removal without causing damage to the delicate membrane surface. CASE STUDY Genesys took its novel technology – Genairclean – to a reverse osmosis (RO) plant that had a history of rapid and consistent fouling to trial the new microbubble, multi-mechanism cleaning approach. The plant is on the site of a major UK salads producer where the salad-wash water and all the process water is recycled. The wash water contains bacteria, soil and clay while the process water is contaminated with bacteria as well as detergents and cleaners used in the wash-down and factory in-place cleaning systems. The wastewater treatment and reuse plant incorporates an advanced membrane bioreactor (AMBR) ultra-fi ltration and RO plant to treat and purify the water for reuse and discharge. The treatment plant is based on pre- treatment and aerated fl ow balancing which is followed by an AMBR, RO and ultraviolet (UV ) disinfection (fi gure 1). Wastewater produced at 1,400 m³/d by the factory requires treatment. After RO and UV disinfection treated water at up to 450 m³/d is fed to the incoming mains water tank for blending prior to entering the factory for salad washing and process use. The plant treats an infl uent chemical oxygen demand total to the balancing tank of up to 480 kg/d depending on factory production. To separate biomass effectively, TECHNOLOGY _________ Steve Chesters managing director of Genesys International ___ Editor's note: in spring 2014 we published an article on how Genesys developed its microbubble-based membrane cleaning system. In this follow up Genesys presents results from a case study of the technology in a wastewater reverse osmosis plant. Microbubble membrane cleaning stems fouling Fieldwork: salad processing provided a challenging trial for a novel membrane cleaning mechanism.

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