A proposal for a test method for assessment of hazard property HP 12 (“Release of an acute toxic gas”) in hazardous waste classification - Experience from 49 waste

International audienceA stepwise method for assessment of the HP 12 is proposed and tested with 49 waste samples. The hazard property HP 12 is defined as “Release of an acute toxic gas”: waste which releases acute toxic gases (Acute Tox. 1, 2 or 3) in contact with water or an acid. When a waste contains a substance assigned to one of the following supplemental hazards EUH029, EUH031 and EUH032, it shall be classified as hazardous by HP 12 according to test methods or guidelines (EC, 2014a, 2014b). When the substances with the cited hazard statement codes react with water or an acid, they can release HCl, Cl2, HF, HCN, PH3, H2S, SO2 (and two other gases very unlikely to be emitted, hydrazoic acid HN3 and selenium oxide SeO2 – a solid with low vapor pressure). Hence, a method is proposed : -1. Measurement of the volume of gases emitted into contact with water or an acid (solid/liquid ratio of 10 L water or acid/kg raw waste, acid 2.5 M HNO3). -2. If gas is emitted at a rate higher than 0.1 L of gas/kg waste in 5 min (limit of quantification of the automated calcimètre used here), checking if one of the cited gases is emitted with electrochemical detection probes or simple qualitative colorimetric methods. -3. If one of these gases is detected, speciation of the emitting substance(s) (calculation by the “worst case” method from elements concentrations, or by specific analytic methods) and checking whether they have a hazard statement code EUH029, EUH031 or EUH032 (a list is provided). For a set of 49 waste, water addition did not produce gas. Nearly all the solid waste produced a gas in contact with hydrochloric acid in 5 min in an automated calcimeter with a volume >0.1 L of gas per kg of waste. Since a plateau of pressure is reached only for half of the samples in 5 min, 6 h trial with calorimetric bombs or glass flasks were done and confirmed the results. Identification of the gases by portable probes showed that most of the tested samples emit mainly CO2. Toxic gases are emitted by four waste: metallic dust from the aluminum industry (CO), two air pollution control residue of industrial waste incinerator (H2S) and a halogenated solvent (organic volatile(s) compound(s)). HF has not been measured in these trials started before the present definition of HP 12. According to the definition of HP 12, only the H2S emission of substances with hazard statement EUH031 is accounted for. In view of the calcium content of the two air pollution control residue, the presence of calcium sulphide (EUH031) can be assumed. These two waste are therefore classified potentially hazardous for HP 12, from a total of 49 waste. They are also classified as hazardous for other properties (HP 7, 10 and 14 for one of them, and HP 10 and 14 for the other one respectively). Given these results, it can be assumed that few common household and industrial waste will be classified hazardous only by HP 12