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PCB007-Aug2019

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44 PCB007 MAGAZINE I AUGUST 2019 Article by Peter Moleux with contributions from Happy Holden The first step in any pollution prevention strategy is to minimize chemical wastes and their rinse waters. There are five general cat- egories of common techniques for pollution prevention in a PCB fabrication facility: 1. New processes to replace sources of pollution 2. Extend the bath's life 3. Rinse water reduction 4. Dragout reduction 5. Ventilation reduction While this list is not all-inclusive, it provides an overview of the types of technologies used around the world that are important to consid- er. In this article, we will examine rinse water reduction. Rinse Water Reduction Most of the waste generated in the manufac- turing of PCBs is from cleaning, plating, strip- ping, and etching. This section describes some of the techniques available for reducing the volume of rinse water used. While we stress the need to reduce individu- al rinse water flow rates when a conventional wastewater precipitation system is anticipated, there may be at least one possible exception. If in excess of 95% of all chemicals are recov- ered, the chemicals do not enter the rinse wa- ter collection system, and a central membrane filtration or deionization system is used to pro- duce a zero-effluent system; then, the need to reduce rinse water flow is reduced. However, one must also consider the capital and operat- ing costs for the central system. One author wrote the following concerning rinse flow rates in the case of a zero-effluent system [1] . "It should also be noted that in a well-engi- neered zero liquid discharge environment, wa- ter conservation is unnecessary. Instead, the focus is total dissolved solids (TDS) budgeting throughout the plant, along with an analysis of specific critical contaminants. Water supply is only limited by the size of the pumps. For instance, to maximize absorption in the fume

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