How Do Treatment Options Compare In Removing Heavy Metals From Semiconductor Wastewater Streams?
By Kody Phillis & Brian V. Jenkins
Microelectronics production generates various types of wastewater. Typically, wastewater contaminants are heavy metals (copper, lead, nickel, cadmium). Proper control of heavy metals in the fab effluent is important for several reasons. First, it is environmentally responsible, and allows the fab to be a good neighbor in its community. Secondly, it can pay solid economic returns and is often the basis for various water reuse/reclaim scenarios.
This article reports on treatment concerns at a fab that makes advanced semiconductors in the northwestern United States. The fab regularly trucks out high-concentration, copper-chelated wastewater. The average soluble copper level in this wastewater is 2,500 to 3,500 parts per million (ppm) at a pH of 0.8. Approximately 4,000 gallons of this wastewater was transported every four days, with an estimated truck-out cost of $15,000 per load. As the fab entered its ramp-up cycle, both the volume of wastewater and the truck out costs escalated. Overall, total site copper discharge limits are 3 pounds per day.
There are several ways to manage heavy metals wastewater. Some of the more common ones, and their respective advantages and disadvantages, are noted here:
Licensed disposal hauling. This method (contracting with a licensed waste hauler) is simple, and requires no investment other than storage facilities that accumulate the wastewater. Advantages of this approach are: simplicity, availability, minimal capital outlay.
Disadvantages are as follows:
- Waste hauling can become expensive.
- The price is usually based on quality, quantity, and distance.
- This disposal approach does not totally eliminate downstream liability.
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