From: Gary Jones (email@example.com )
Date: Tue, 25 Sep 2001 21:18:16
The key to the classification of the used plates with respect to their status as a hazardous waste is the amount of silver remaining in the plated after use. According to EPA's definition of a hazardous waste, a waste steam that contains more than 5 ppm silver is considered hazardous. It is important to recognize that the amount of silver is to be determined via a special test called the Toxicity Characteristic Leaching Procedure (TCLP).
When you had the plates tested for residual silver content, did you use the Toxicity Characteristic Leaching Procedure (TCLP)? This is important, as a 1% concentration of silver is about 10,000 ppm. However, a total silver concentration of 10,000 ppm does not necessarily equate into a 10,000 ppm as measured by TCLP. In addition, if your developing solution contains more than 5 ppm silver, then it to is considered hazardous unless you have permission to discharge to a sewer authority, but you will have to most likely treat it to recover the silver.
Lastly, if you live in California, there are different tests in addition to the TCLP for classifying a hazardous waste. They are more stringent, but if you are not located in California, then we don't need to go into detail.