A novel method to calculate the size of representative waste samples based on particles size

Abstract

A novel approach to determine the size of samples of granular wastes is proposed, forwarding the concept of the “number of particles”, as previously introduced by the authors. To be representative with a minimum error, it was demonstrated that at least 100 particles showing the presence of the measurand, shall be collected in the sample. Waste particles are usually characterized by size-concentration relationships. However, in waste sampling standards they are not explicitly considered when estimating the size of the sample. In this context, this paper extends this requirement to the number of particles “rare is size”, belonging to the less represented size fraction in the waste to be characterized. The number of particles is then transformed into a mass by a formulation that avoids using unrealistic assumptions on particles features. Results derived from the application of the two formulations on 5 different types of waste show that their equivalency relies on how similar are, the proportions of particles rare in concentration and rare in size in the batch to analyse. Here, preliminary knowledge on particles physical features and distribution of the measurand is key to derive coherent values for mass of samples. Finally, the need to perform on-site size reduction is discussed for cases where the application of both the conventional and novel approaches could have leaded to unpractical management of too large-sized waste samples.