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Previous articles summarized the difficult first two years of operating the microfiltration/reverse osmosis/nanofiltration (MF-RO-NF)plant in Chandler, Arizona, a Phoenix suburb. It reclaims industrial wastewater fromsemiconductor manufacturing to potable standards to recharge an aquifer. This updatepresents subsequent improvements in pretreatment and processing that have loweredoperating costs, cleaning frequencies, and rate of membrane replacement.The cutting-edge, award-winning facility commenced operationsin July 1996, reclaiming wastewater generated by Intel's Fab 12, one of the world'slargest semiconductor manufacturing facilities. The reuse plant was designed beforeFab 12 was operating, so site-specific data were not available. At start-up, it was foundthat the raw water would need pretreatment to protect RO from high Silt Density Index(SDI) and turbidity values. Many in the RO industry would consider these impossibleoperating conditions. It was difficult, but not impossible. As a temporary solution, fieldrevisions were implemented to allow operation of the polyamide thin film compositemembrane, including: lower flux, lower recovery, increased velocity across themembrane surface, lower feed pH (to address calcium phosphate scaling), frequentcleanings, and experimental cleaning methods. These were relatively successful, but,as anticipated, there were problems: chemical cleanings were required often, cartridgefilter replacement rate was frequent, and service life of the spiral wound RO elementswas short. Subsequent modifications included adding prefiltration by UF, replacing theUF with MF, and implementing pre-chloramination to control biofouling. Today, the planthas injected over 2.5 billion gallons of potable water.The paper summarizes the history of the plant, water quality, equipment descriptions,replacement of cartridge filters with automatic backwashable screens, cleaning methods, and current operating practices. Includes 4 references, tables, figures.

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Edition: Vol. - No. Published: 03/01/2005 Number of Pages: 10File Size: 1 file , 540 KB