• Neither TCLP (Toxicity Characteristic Leachate Procedure) nor the “Rule of 20” may be used on a liquid waste for the purpose of determining the characteristic of toxicity.
• The point of TCLP analysis is to extract a leachate from a representative solid sample of waste and determine the concentration of specified toxins in the liquid.
• Regulated toxins are identified by USEPA in Table 1 of 40 CFR 261.24(b).  They include:
  • Arsenic (D004)
  • Lead (D008)
  • 2,4-D (D016)
  • Lindane (D013)
  • Silver (D011)
  • Toxaphene (D015)
  • 2,4,6-Trichlorophenol (D042)
  • More…

• The “Rule of 20” (I believe this is what the questioner meant by “20 x rule”) is a less expensive option than TCLP for analysis to determine a characteristic of toxicity for a solid.  The procedure for using the Rule of 20 on a solid sample is briefly summarized as follows:
  • Analyze to determine the total concentration of regulated toxin(s) in the sample.
  • The total results are then divided by 20 to determine the Maximum Theoretical Leachate Concentration (MTLC).
  • The MTLC is compared to the regulatory threshold of the toxin(s) at §261.24.
  • If the MTLC does not equal or exceed the regulatory thresholds, then the sample cannot exhibit the characteristic of Toxicity.
• A liquid sample of a waste is analyzed directly for the total concentration of toxins.  The total results are compared directly to the regulatory thresholds to determine if it exhibits the characteristic of Toxicity.
• To better understand the Rule of 20, Please read:  How to Determine the Toxicity Hazardous Waste Characteristic Without TCLP

I hope this helps.  Please contact me with any other questions.

Conclusion:

Analysis of a sample to determine the characteristic of Toxicity is just one step in the responsibility of a hazardous waste generator to conduct a hazardous waste determination.  Using the Rule of 20 can save you a lot of money in lab costs.  Contact me to determine if there are any other methods available to you to save money and ensure compliance.