Application of Test
The Environmental Compliance Supervisor (the "gatekeeper") at a typical municipal landfill (as defined by RCRA Subtitle D) uses TCLP data to determine whether a waste may be accepted into the facility. If TCLP analytical results are below the TCLP D-list maximum contamination levels (MCLs) the waste can be accepted. If they are above these levels the waste must be taken to a hazardous waste disposal facility and the cost of disposal may increase from about $20/ton to as much as $500/ton.
TCLP comprises four fundamental procedures:
- Sample preparation for leaching
- Sample leaching
- Preparation of leachate for analysis
- Leachate analysis
As extremely contaminated material is expensive to dispose, grading is necessary to ensure safe disposal and to avoid paying for disposal of "clean fill." The TCLP procedure is generally useful for classifying waste material for disposal options.
A concern has arisen in recent years regarding TCLP analysis in that the test is based on the assumption that the waste material will be buried in landfill along with organic material, however organic matter is rarely buried with other waste anymore (composting usually applies). In light of this issue, other leachate techniques may be more appropriate.
Spent abrasive or soil from a construction site usually need to have a TCLP for lead done to determine where the waste goes next.
In the TCLP procedure the pH of the sample material is first established, and then leached with an acetic acid / sodium hydroxide solution at a 1:20 mix of sample to solvent. For example, a TCLP jug may contain 100g of sample and 2000 mL of solution. The leachate mixture is sealed in extraction vessel for general analytes, or possibly pressure sealed as in zero-headspace extractions (ZHE) for volatile organic compounds and tumbled for 18 hours to simulate an extended leaching time in the ground. It is then filtered so that only the solution (not the sample) remains and this is then analyzed.
Read more about this topic: Toxicity Characteristic Leaching Procedure
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