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 from
semiconductor manufacturing to potable standards to recharge an aquifer. This update
presents subsequent improvements in pretreatment and processing that have lowered
operating costs, cleaning frequencies, and rate of membrane replacement.
The cutting-edge, award-winning facility commenced operations
in July 1996, reclaiming wastewater generated by Intel's Fab 12, one of the world's
largest semiconductor manufacturing facilities. The reuse plant was designed before
Fab 12 was operating, so site-specific data were not available. At start-up, it was found
that 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 impossible
operating conditions. It was difficult, but not impossible. As a temporary solution, field
revisions were implemented to allow operation of the polyamide thin film composite
membrane, including: lower flux, lower recovery, increased velocity across the
membrane surface, lower feed pH (to address calcium phosphate scaling), frequent
cleanings, and experimental cleaning methods. These were relatively successful, but,
as anticipated, there were problems: chemical cleanings were required often, cartridge
filter replacement rate was frequent, and service life of the spiral wound RO elements
was short. Subsequent modifications included adding prefiltration by UF, replacing the
UF with MF, and implementing pre-chloramination to control biofouling. Today, the plant
has 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.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 540 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 10 |
| Published : | 03/01/2005 |
