Challenge

Increased demand led this fab to look at methods to increase available water availability while minimizing initial capital cost and floor space.

Solution

The system consisted of a conventional makeup system using double pass RO, UV, mixed beds, etc.  Expanding this equipment to allow for more water availability in the loop would require a noticeable increase in capital and operating costs, and consume floor space that was not readily available.  The polishing system consisted of a UF of which 5% of the UF reject would feed back ahead of the RO for small particle reduction.

By installing a reject UF in the reject line, 95% of the reject flow was directed back directly to the UPW tank, thereby reducing the load on the makeup system.  The remaining reject stream continued to feed back ahead of the makeup ROs.

Results

The reject UF was able to take 50 gpm of the reject stream and recover 95% (47.5 gpm) and direct the permeate directly back to the UPW storage tank resulting in an immediate makeup capacity boost of 47.5 gpm.  The makeup system expansion would have cost about >$300,000 installed as compared to <$100,000 for the reject UF installed.  This resulted in:

• capital savings of >$200,000
• increased quality and operational reliability by reducing the makeup demand
• reduced operating costs (power for ROs, makeup mixed bed resin, manpower for makeup maintenance, etc.)
• minimal floor space consumption (15 sq. ft. plus access area)
• quicker upgrade than a major makeup system expansion

This was a very quick, simple and inexpensive way for the customer to increase makeup capacity by about 10%.  The same concept is being implemented at another major fab in the Southwest for the same reasons.