Lessons from a large dataset of aquatic ecotoxicological test results for routine HP 14 classification of wastes: the case of bottom and fly ashes in the Italian framework

One of the main goals of the current EU legislation regarding wastes is to protect the environmental and human health against their adverse impacts and promotes a correct waste management. In particular a crucial point is the Hazardous Property HP 14 'Ecotoxic' defined by the EU Regulation 2017/997 as "waste which presents or may present immediate or delayed risks for ecosystems". HP14 classification is based on chemical analyses of waste and quantification of its hazardous substances content, without specific details on how to assess its ecotoxicity (e.g. which test battery has to be applied or how different and difficult wastes should be ground and sieved and subsequently treated to obtain extracts suitable for performing bioassays). In fact, depending on the experimental approach, a different classification could be made in different EU Member States, posing potential difficulties when wastes have to be transported across European borders. Therefore specific recommendations and methodologies for HP14 classification are needed to achieve harmonisation and standardisation of test methods for classification of waste at European level. The study showed some methodological aspects to solve critical problems for HP14 classification of solid waste, in particular for bottom and fly ashes (BA and FA). About 200 samples were evaluated according to CLP Regulation methods using OECD Guideline No. 29 (2001) to prepare the sample, whilst also taking into account OECD Guideline 23 (2019), which is applicable to testing this difficult metal-containing waste. Ecotoxicological tests were performed on both BA and FA and the effect concentrations (EC50) were calculated statistically. Most of the samples (69% and 86% for FA and BA, respectively) were classified as non-ecotoxic A decision tree for HP 14 classification of waste is proposed , to be adopted in similar cases for the HP 14 classification of ashes from municipal solid waste for optimizing the waste classification process