When Will a Leachate Sample Never Fail the Leachate Criteria?

Outline of Presentation 1. Why Environmental Contaminant Mobility Potential is important

2. How Mobility is Sometimes Assessed

3. The “Standard Leachate Test” War Chest i. TCLP ii. SPLP iii. ASLP iv. LEAF

4. The Theoretical Leachate Value

5. Suggested Decision Process

6. Conclusions and Way Forward

7. Questions?

Source – Pathway - Receptor

1. Why Environmental Contaminant Mobility Potential is important

2. How Mobility is Sometimes Assessed • Simple fundamental environmental chemistry (e.g. sulphide solubility) • Elegant geochemical modelling • Empirical testing (leachate generation techniques) • “Weight-of-evidence” approach • IMPORTANT to determine DQOs (i.e. Simulation Vs. Characterisation) • Let’s consider leachate testing…

3. The “Standard Leachate Test” War Chest • Many tests out there…. • TCLP (Toxicity Characteristic …) • SPLP (Synthetic Precipitation…) • ASLP (Australian Standard….) • LEAF (Leaching Env Assessment Framework) • … and • ASTM D3987-85 • EP and MEP (Method 1310A and 1320) • BS EN 12457 • And many more – let’s consider the first four..

3.1 TCLP (Toxicity Characteristics Leaching Procedure)

• Method 1311 (July 1992) • Split waste if <0.5% Total Solids • Solids to <9.5mm sieve • Acetic Acid / NaOH • Solution 1 pH 4.93 (if >pH5) • Solution 2 pH 2.88 (if <pH5) • 18+/- 2hrs end-end rotation • Filter/combine analyse

3.2 SPLP (Synthetic Precipitation Leaching Procedure)

• Method 1312 (Sep 1994) • Split waste if <0.5% Total Solids • Solids to <9.5mm sieve • Nitric/Sulphuric/Water • Solution 1 pH 4.20 (if East of M Rr)!! • Solution 2 pH 5.00 (if West of M Rr)!! • 18+/- 2hrs end-end rotation • Filter/combine analyse

3.3 ASLP (Australian Standard Leaching Procedure)

• AS 4439.1-1999 • Split waste if <0.5% Total Solids • Solids to <2.4mm sieve • Solution 1 – Reagent water • Solution 2 – Tetraborate pH 9.2 • Solution 3 – local water • 18+/- 2hrs end-end rotation • Filter/combine analyse

3.4 LEAF (2013) (Leaching Environmental Assessment Framework)

Four separate procedures used individually or in combination: • Method 1313 –pH varying parallel batch extraction • Method 1314 – Up-flow percolation column • Method 1315 – semi-dynamic tank leaching • Method 1316 – solid ratio parallel batch extraction

• So many choices – not enough time…

4. The Theoretical Leachate Value

• Leachate Tests use a simple solid to liquid ratio

• TCLP, SPLP and ASLP all use 100g in 2L of Eluant

• Dilution of 0.05 or 20 times • Now, assume 100% mobility (i.e. all the

contaminant is mobilised form the solid to the eluant)

• Worked Example…..

Lead (Pb) Case Study 1

• Total Lead = 250 mg/kg • Theoretical TCLP = (250*.05) = 12.5 mg/L (if 100% leached) • TCLP1 = 5mg/L so sample could theoretically fail so • Complete TCLP test to assess empirical leachability

Lead (Pb) Case Study 2

• Total Lead = 80 mg/kg • Theoretical TCLP = (80*.05) = 4 mg/L (if 100% Leached) • TCLP1 = 5mg/L so sample could NEVER FAIL the TCLP threshold level!!!

6. Conclusions and Way Forward • Ensure leachate test is consistent with DQOs

(Simulation Vs. Characterisation) • Understand advantages and limitations of “war chest” • Work closely with Analytical Laboratory to achieve DQOs • Collaborate to stage the analytical work, with a decision point

immediately after total concentrations assessment milestone has been reported!

• Apply Theoretical Leachate Value to save time and money!

7. Questions? Ross.mcfarland@aecom.com