87    WASTEWATER MANAGEMENT IN SEMICONDUCTING
ELECTRONIC CRYSTAL MANUFACTURING
FACILITIES
Joseph M. Wong, Project Manager
Brown and Caldwell Consulting Engineers
Pleasant Hill, California 94523
INTRODUCTION
The last 15 to 20 years have seen a rapid evolution of electronic technology. The semiconducting
electronic crystals industry is growing in the United States as well as in other parts of the world. A
major part of that evolution has been the development of single crystals with unique structural and
electronic properties. These crystals are essential parts of most microelectronic devices. The manufacturing processes require large quantities of chemicals and water for etching and cleaning. Consequently, wastewater from these plants may require extensive treatment before discharge. Figure 1
shows the basic manufacturing processes for semiconducting electronic crystals and some of the
wastes produced.1
ENVIRONMENTAL REGULATIONS
The U.S. Environmental Protection Agency (EPA) promulgated regulations to limit the discharge
of pollutants into navigable waters and publicly owned treatment works (POTW) from semiconductor
and electronic crystal manufacturing facilities on April 8, 1983.2 Under the title "Electrical and
Electronic Components Point Source Category Effluent Limitations Guidelines, Pretreatment Standards, and New Source Performance Standards," these regulations provided effluent limitations for
"best practicable technology" (BPT), "best available technology" (BAT), "best conventional technology" (BCT), "new source performance standards" (NSPS) for direct dischargers, and pretreatment
standards for new and existing sources (PSNS and PSES) of indirect dischargers. Table I presents the
effluent limitations for the Electronic Crystals Subcategory of these regulations.
Materials listed as comprising total toxic organics (TTO) in these regulations include 30 priority
organic compounds2 that were detected in significant quantities during the sampling and analytical
EPA program conducted as a basis for the regulation. Since periodic effluent sampling and analysis
for these numerous organics could be very expensive, this regulation allows, as an alternative to the
usual monitoring requirements, plants to certify that spent solvents are not discharged into the
wastewater, but are collected for contract disposal or for sale to reclaimers. In requesting that no
monitoring of TTO be required, plants must submit a solvent management plan to the permitting
authority. This plan then becomes a provision of the permit.
WASTEWATER CHARACTERISTICS
EPA has developed the limitations and standards in these regulations to cover a typical plant for
this industry. However, in specific cases, such as more stringent state water quality standards, the
permitting authority may have to establish permit limits on toxic or conventional pollutants that are
not covered by this regulation. Furthermore, discharges to POTW are required to comply with local
ordinances that may be more stringent than these pretreatment limitations. Based on the author's
experience with integrated silicon wafer manufacturing plants, other significant water borne pollutants that may occur in these wastewaters include biochemical and chemical oxygen demand (BOD/
COD), nitrate, ammonia, and chromium. Chromium is regulated under the Metal Finishing Category
Regulations.
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