Development of a Method for Determining the Leachability of Organic Compounds from Solid Wastes

This study was undertaken to develop a method for assessing the potential mobility (leachability) of purgeable and semivolatile organic priority pollutants from solid waste materials. The objective was to develop a method that would (1) model the leachability that might occur in a municipal landfill environment, (2) be relatively simple and easily implemented by production-type laboratories at a relatively low cost, and (3) give reproducible results.

The solid wastes studied included aqueous sludges, organic chemical wastes, and inorganic solids. The leaching media studied included distilled water, acetate and citrate buffers, reducing agents, and surfactants. A tumbling device designed by the National Bureau of Standards was used to achieve reproducible mixing of the specimen and the leaching medium with a minimum of particle-size reduction. The device tumbles the mixture of the specimen and leaching medium end over end in a closed container, and is applicable to nearly all solid waste materials.

Previous studies reported in the literature on solid waste leaching tests have generally emphasized the leachability of toxic metals. In order to permit a comparison of our results with previously reported results, the leachates generated were analyzed for metals as well as for organic compounds. Metals were determined by inductively coupled argon plasma spectroscopy (ICAP) and by flame atomic absorption spectroscopy (AAS). Purgeable organics were determined by gas chromatography-mass spectrometry (GC-MS) using Environmental Protection Agency (EPA) Method 624. Phenols, pesticides, and neutral organics were determined by GC-MS using EPA Method 625 with minor modifications. Studies on the precision of the leachability, metal analyses, and GC-MS analyses were performed as an important part of the overall analytical program.

The solid waste leaching procedure developed was shown to be reproducible, easy to use, and suitable for many types of wastes and analytes. Distilled water was found to be as effective as other media studied for leaching organic compounds. Citrate buffer was often much more aggressive than acetate buffer for leaching metals. The aggressiveness of citrate buffer was highly metal and specimen dependent. The degree to which the procedure reproduces the leaching of components in a codisposal environment, which would depend upon the leaching medium used and site-specific conditions, is unknown at this time.