With initial funding from the City, the Silicon Valley Pollution Prevention Center (SVPPC) retained Rosenblum Environmental Engineering to develop proposals for water efficiency demonstration projects at high-tech manufacturing plants with large wastewater discharges to the SJ/SC WPCP. Two proposals, for a disc-drive media plant and a semiconductor plant, were completed and submitted for consideration of funding as part of the industrial component of the South Bay Action Plan.

Besides detailed scopes of work for the demonstration projects, both proposals include estimations of wastewater reductions and evaluations of cost-effectiveness for several full-scale options. Comparing these options reveals that recycling is not cost-effective unless integrated with production-process efficiency improvements. As a result, both proposals focus heavily on process efficiency improvements.

Disc Drive Options This disc-drive media plant produces 100,000 discs/week. Nickel-plated discs are ground to a precise thickness using an abrasive slurry, and then polished and washed using chemical cleaners, Deionized Water (DI-Water), and Ultra Pure Water (UPW). The 1997 baseline wastewater discharge volume was 225,000 gpd. A 50% increase in production throughput is anticipated by 1999.

Three options were evaluated for 1999:

1. Without Recycling or Process Efficiency, wastewater volume and nickel load will increase significantly beyond permit limits. Capital costs and annual operating costs will be much higher than 1997, so there will be no direct payback on the investment.
2. With Recycling Only, wastewater volume and nickel load will decrease significantly, eliminating potential permit compliance problems. Capital costs and annual operating costs will be higher than for both other 1999 options (and the 1997 baseline), making it the most expensive option for 1999.
3. With Recycling and Process Efficiency, wastewater volume and nickel load will be lower than with recycling only (compared to 1997, wastewater will decrease 77% and nickel 87%). Large reductions in chemical usage, DI-Water, and UPW will reduce operating costs even below 1997 levels, providing annual savings to pay for additional capital costs. Compared to not implementing recycling or process efficiency, savings of $3.4 million in annual operating costs will pay back the additional $1.0 million in capital costs in 0.3 years.

Fig.1 shows the changes in physical parameters;

Fig.2 shows capital and operating costs.

Semiconductor Options This semiconductor plant has three separate "Fabs", of which one has been recently modernized and the second will be upgraded in 1998; no changes are currently anticipated for the third Fab. Ultra Pure Water (UPW) is supplied for rinsing throughout the plant. The 1997 baseline wastewater discharge volume was 300,000 gpd. Production will increase as the second modernized Fab comes on-line in 1999.

Previous experience at other facilities owned by the company and within the Sematech consortium indicate that efficiency improvements are necessary for cost-effective recycling of Fab rinse-wastewater. Thus two options were evaluated for 1999:

1. Without Recycling or Process Efficiency, sewer discharges will increase beyond the current capacity limit in the permit. Capital costs and annual operating costs will be much higher than 1997, so there will be no direct payback on the investment.
2. With Recycling and Process Efficiency, sewer discharges will decrease 55% compared to 1997, providing a very large margin of safety below the capacity limit in the permit. Large reductions in City-Water and UPW will reduce operating costs even below 1997 levels, providing annual savings to pay for additional capital costs. Compared to not implementing recycling or process efficiency, savings of $0.8 million in annual operating costs will pay back the additional $2.4 million in capital costs in 3.1 years.

Fig.3 shows the changes in sewer discharge, City-Water demand, and UPW usage;

Fig.4 shows capital and operating costs.

Implications Table 1 shows that recycling and process efficiency projects can potentially provide very large reductions in wastewater discharges, with savings in operating costs that can pay back capital costs in a relatively short time. In particular, wastewater discharges can be reduced more than 55% below 1997 levels, and the paybacks are considerably less than the 5-year guideline for contingency measures in the South Bay Action Plan.

Rinse-water recycling has been successfully implemented in many semiconductor and disc-drive plants, and is rapidly increasing in water- scarce areas. Recycling is already practiced in 40% of plants belonging to Sematech members. Process efficiency improvements often accompany the frequent modifications required to provide new products and meet more demanding quality standards. For example, new wafer rinsing equipment can remove more contamination in less time, while using 80% less water (for the same surface area). Although widely applicable in general, recycling and improving process efficiency still require detailed evaluations of site and product specific impacts, and pilot-testing of equipment to verify performance under a wide variety of conditions. The proposed demonstration projects will provide such evaluations, and help encourage local implementation of full-scale projects.

To ensure valid results from the evaluation, active participation of all departments within the plant (e.g. production, facilities, environmental, and purchasing), chemical suppliers, and equipment vendors is essential. This will require a considerable organizational commitment to the demonstration projects. Without such commitments, reductions in water, wastewater, and chemical volumes will be insignificant, and recycling ratios for rinse-wastewater will be very small. As a result, estimates of operational savings for a full-scale project will be too low, and capital costs will be unnecessarily high. The willingness of managers to lead their organizations into active participation in the demonstration projects is vital.