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Semicon Mfg. Water Reuse

I have seen a number of semiconductor fabrication shops use water
sequentially, but not in a counter-current arrangement.  

Examples include:

	Vacuum Pump Cooling --> DI Make-up --> Wafer Fab Rinses

	Wafer Fab Rinses --> Neutralization --> Cooling Tower Make-up

	Wafer Fab Rinses --> Neutralization --> Fume Scrubber

Some shops looked at recycling their treated (neutralized) wastewater
back to the DI feed, but most found that the payback period was longer
than 5 years (I see in my files one recycling project with a payback of
8.4 years, plus others with much longer periods).  

Also, because the value of semiconductor product is high, there has been
a reluctance at most sites to risk contamination by rinsing wafers with
recycled water.

In 10/94, the City of San Josť issued a summary of "Industrial Mass
Audit Studies" conducted by local firms looking for ways to reduce
copper and nickel discharges.  This report includes a few projects
considered by semiconductor fabricators.  Please let me know if you
would like me to send you some project summaries from this report.

Tom Barron
(510) 283-8121