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A manufacturer of large circuit boards, such as those for microwave and tower antennas needs to reduce copper concentrations in its wastewater. The copper concentrations range from 3-10ppm per four day composites.
The manufacturer needs to reduce copper concentrations to <2ppm.
The basic operation entails a subtractive manufacturing process. First, copper clad boards are sheared to size, drilled and the holes are drilled and plated with an electroless copper plating method. Substrates consist of fiberglass or teflon. Tin and copper electroplating operations are used as well. Films for the boards which detail customer specifications are obtained from an outside source and are copied using an ammonium hydroxide blueprint process. An image is cast onto the board and heat lamination applies an etch resist. Each sheet is exposed to ultraviolet light whereby the cast image appears on the board. Chemical etching, using sulfuric peroxide or ammonium hydroxide, removes all copper from the board except the areas of image. Washing and rinsing of the boards occurs at various stages of manufacturing.
The spent ammonium hydroxide solution from the etching process is returned to the manufacturer for recycling.
The sulfuric peroxide solution is re-used on-site and eventually the soluble copper is plated out and recycled.
All other wastewater created within the facility is sent to a 3800 gallon capacity pH adjustment tank; it is the only on-site treatment conducted. pH typically runs high, around 9, pH adjustment is necessary at times to keep the pH above 5 (permit limit). Flow through the treatment system is around 12,000 gal/day.
The manufacturer has been approached by a variety vendors with expensive treatment equiptment and is unsure of the best technology to invest in. They request information regarding any proven treatment or
prevention technologies and other strategies to meet the new discharge limits (< 2ppm).