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What's in that "aqueous" waste?

 

One of the less rigorous definitions in the Radiation Safety Handbook is "aqueous," as in "aqueous waste." The definition says "Aqueous waste denotes any solution of which the primary constituent is water and any soluble organic and inorganic constituents, all present in forms and quantities that do not result in phase separation or precipitation." What the definition does not say about the "soluble organic and inorganic constituents" is that the presence of even small amounts of hazardous or incompatible chemicals can turn that waste jug into an expensive problem. Most of the chemicals in your lab will fit one or another of the hazardous chemical definitions on ORS web page http://www.research.northwestern.edu/ors/hazcomm/index.htm#hazchemdef. There are many chemicals we must not release to the sanitary sewer, and we ask that you carefully consider what you put into liquid waste containers and also describe the contents fully on the radioactive waste card.

 

Three indicators of potential problems are phase separation, precipitation, and high or low pH. When we see phase separation we have to sample and analyze each phase and separate each for disposal. The problem with precipitates is that ORS cannot determine the chemical composition and we have to analyze the precipitate separately for radioactive content. Wastes with very high or low pH can be hazards to the people who have to handle them and they must be neutralized before disposal. The acceptable pH range is 5 to 9.

 

Make every effort to avoid generating mixed wastes. Even small amounts of miscible chemicals such as methyl alcohol in water are mixed wastes in concentrations as low as 6%. We have paid disposal costs upwards of $2,000 per gallon for some mixed wastes -- costs that potentially are passed back to the generator.

 

The law also requires us to report the presence of chelating agents, specifically polycarboxylic acids such as EDTA and DTPA. If you put any of these into any waste container you must list them and their concentration on the waste card.

 

Look at your liquid radioactive waste today. If you find the problems discussed in this article, call us and we will work with you to resolve them. List all hazardous chemical components and their concentrations on the waste card. Review your protocols and procedures and change them as necessary to avoid generating mixed wastes. Contact ORS before generating waste if you have questions about what is acceptable.