A publication of Work On Waste USA, Inc., 82 Judson, Canton, NY 13617 315-379-9200 MARCH 1995
A key step in the bureaucratic detoxification of waste from municipal solid waste (MSW) incinerators is the willful avoidance of regulation to require the measuring of the total content of toxics in the ash. Instead, all the emphasis is placed on leaching tests supposedly designed to simulate the acidic leaching conditions in a municipal waste landfill. While it is extremely important to protect surface and ground water from these toxics it is equally important to protect human beings and other species from direct exposure to this ash. Unfortunately, when incinerator operators pass the inappropriate TCLP testing, press releases and newspaper headlines usually and loudly proclaim ash tests show ash safe. As a result, workers in the incinerators, ash truck drivers, workers at the landfills and residents near landfills, incinerators and truck routes are not made aware of how dangerous this material is if it is inhaled or ingested. This actually applies not only to the fly ash but also to the lime from the air pollution control devices which is extremely corrosive and would tend to irritate the membranes in the respiratory system. The following table gives a summary of the ranges of various toxics found in ash from municipal waste incinerators.
Concentrations of Substances in MSW Bottom and Fly Ash.
HAZARDOUS WASTE CLASSIFICATION. Under federal regulations there are four ways a substance may be classified hazardous and thus be required to be sent to a hazardous waste facility. It may be ignitable, corrosive, reactive or toxic. As far as incinerator ash is concerned there are two problems areas. Firstly, with the presence of large quantities of lime in the fly ash generated in modern incinerators the ash may fail the corrosive characteristic. The corrosive label is given to materials which produce a solution of pH less than or equal to 2, or greater than or equal to 12.5. Samples of fly ash from incinerators fitted with lime scrubbers frequently produce solutions with a pH greater than 12. The second concern about ash is its toxicity. This is determined by a LEACHING TEST. Up to March 1990 this leaching test was the EP Tox Test (Extraction Procedure Toxicity Test). Since then it has been replaced with the TCLP Test (Toxic Characteristic Leaching Procedure Test). Both tests were supposedly designed to mimic the acidic conditions generated by rotting garbage in a municipal waste landfill.
THE EP TOX TEST. In this test 100 grams of the ash is placed in a given quantity of water and dilute acetic acid added until the solution has a pH of 5. This solution is stirred constantly for 24 hours with the acidity maintained at pH 5, with more additions of acetic acid, if necessary. After 24 hours the solid ash is filtered off and the solution is made up to a total of 2 liters with water. This final solution is then examined for pollutant levels which have dissolved out of the solid ash. Of particular relevance for incinerator ash are the levels of several toxic metals, particularly lead and cadmium. If these metals are present at levels one hundred times* the safe drinking water standards then the material in question fails the test and is designated EP Toxic and should be classified as hazardous waste.
Table B below lists the safe drinking water standards for cadmium and lead and the EP Tox levels. Table C gives a summary of the percentage of ash samples which were failing the EP Tox test in the 1980s.As can be seen from Table C, 94% percent of fly ash, 36% of bottom ash and 40% of combined ash were failing the EP Tox test. We have already pointed out the huge financial implications of these results for the incinerator operators, however, the EPA in the 1980s dragged its feet on enforcing these regulations with respect to ash disposal.
Table B Table C1 Leaching Toxicity Levels used in Table C Safe Drinking EP Tox Test Water Standard Toxicity Leaching Levels CADMIUM 0.01 mg/liter or 0.01 ppm 1 mg/liter or 1 ppm LEAD 0.05 mg/liter* or 0.05 ppm 5 mg/liter or 5 ppm * NOTE ON LEAD. Effective on December 7, 1992, the USEPA dropped the safe drinking water standard (SDWS) for lead from 0.05 to 0.015 ppm. However, when the USEPA tightened the SDWS for lead it did not change the toxicity levels for leaching tests. To be consistent, the toxic leaching levels for lead should now be set at 1.5 ppm (i.e., one hundred times the new SWDS.) All other metals of concern from MSW incinerator ash are classified as toxic if they exceed levels one hundred times the SWDS in the leaching tests. If toxicity levels for lead in leaching tests were set at at 1.5 ppm in Table B, many more lead samples would have failed.
Testing with water instead of acetic acid. One of the first responses to these test results by incinerator operators was to suggest that it was unfair to mimic the acid conditions of a municipal waste landfill because the ash was going to be sent to monofills. Thus, the claim went, the ash would not come into contact with rotting garbage and the testing with acid was not appropriate. A better test would be to test the ash with water. One of the first places where the ash was tested with water was in Claremont, NH. In 1987, 20 samples of ash were tested with acid and water. 19 of the 20 tests with water failed for lead. In fact, in some cases, higher levels of lead were leaching out with water than with dilute acetic acid. (A full copy of these test results will be made available for anyone who wants them.) Part 3 of this ash series will explain leads peculiar solubility profile as the pH of the leaching medium changes, and the impact of this on the new TCLP test.
1. U.S. Congress, Office of Technology Assessment (OTA), Facing Americas Trash: Whats Next for Municipal Solid Waste. Published in 1992 by Van Nostrand Reinhold, NY, NY, ISBN 0-442-01048-6. Table A from Table 6-6 on page 248. Table C from Table 6-8 on pg. 253. Originally published by the OTA in October 1989, OTA-0-24 (Washington, DC: U.S. Govt. Printing Office.)
Editors: Ellen & Paul Connett, 82 Judson Street, Canton, New York 13617. Tel: 315-379-9200. Fax: 315-379-0448.