The Illusion of Dilution

How much is too much This question comes up frequently in discussions about waste disposal. After all, a little hazardous material should not cause much damage or be in violation of regulations. It will simply disappear if sufficiently well mixed with a 

At the semiconductor plant, a small amount of hydrofluoric acid was used in the processing. After neutralization, it was discharged into the large flow of water from the plant. When waste water in the area near the plant showed fluoride levels well in excess of the permissible 5ppm, the manufacturer became suspect. Refusing to believe that he could cause such contamination, he called in a consultant, who calculated that the water from this plant could contain as much as 60 ppm fluoride. This still sounded impossible to the manufacturer, but analysis confirmed the calculated result. Steps were soon taken to correct the situation. 

It is always surprising to find how even very small quantities of some chemicals can create contamination or waste disposal problems. As a result, such matters should be given high priority when planning a new or modified laboratory, purchasing new equipment, or introducing new procedures. 

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