This paper have evaluated and compared two HP14 classification frameworks: (i)
a calculation method (summation) for mixtures, and (ii) leaching tests. The two frameworks were evaluated
by surveying and evaluating ecotoxicological data for Cu, Zn, K and Ca species in bottom ash from
incinerated waste, together with geochemical speciation modelling. Classification based on the summation
method proved to be highly sensitive to the choice of speciation and ecotoxicological classification.
This results in a wide range of critical concentrations triggering hazardous classification (in particular for
Cu and Zn). Important parameters governing the availability of toxic elements, such as transformation
from one species to another
Geochemical modelling revealed that a testing strategy built on CLP based leaching tests (liquid/solid
ratio (L/S) P 10,000, pH range 5.5–8.5) avoids bias and is superior to the summation method with respect
to both precision and accuracy. A testing strategy built on leaching tests, designed for risk assessment
purposes, (L/S ratio of 10, natural pH of the ash) severely underestimate the hazard associated with
the presence of toxic compounds (Cu and Zn), while simultaneously falsely indicate a hazardous
due to the presence of non-toxic compounds (Ca and K). However, the testing methods adopted by
CLP are problematic from a practical and functional point of view. To conclude, the L/S ratio and pH were
found to be critical for hazard classification based on leaching test methods. Further studies are needed to
develop a relevant, practical and functional testing strategy for HP14 hazardous waste classification.