Leaching and Ecotoxicity Tests as Methods for Classification and Assessment of Environmental Hazard of Solid Wastes
Vaajasaari, Kati (2005)
Vaajasaari, Kati
Tampereen teknillinen yliopisto
2005
Kuvaus
Doctoral thesis, Tampere University of Technology, Publication 540
Tiivistelmä
The importance of developing methods for the hazard assessment of solid wastes is steadily increasing worldwide. The main objective of this thesis was to develop a new approach to waste hazard classification that combines leaching and ecotoxicity tests, since the determination of total concentrations of substances in complex mixtures of unknown composition, which is a characteristic of many wastes, does not provide an accurate estimation of the overall environmental impact of solid wastes.
Chemical classification was carried out by comparing total concentrations of key hazardous substances in the wastes studied with the limit values set for hazardous wastes, and comparing the leached amounts of the substances with the limit values proposed by the EU. Four wastes studied from the metal and forest industries contained predominantly inorganic compounds and ten from the furniture and resin industries mainly aromatic or aliphatic organic compounds. Six soil samples contaminated by petroleum products were studied in order to evaluate their environmental hazard after remediation. Various types of leaching tests were used to study the leaching profiles of key hazardous substances in four predominantly inorganic wastes. Onestage or multistage batch leaching tests were also used to study the leaching of volatile organic compounds from the organic wastes and that of petroleum products from the soil samples. The ecotoxicity of substances leached out from the wastes was studied from the eluates of batch leaching tests with different combinations of aquatic ecotoxicity tests: microbial tests, water flea and algal tests, electron transport assay (RET) and plant tests. In addition, the ecotoxicity of oilcontaminated soils was studied directly from solid materials with plant seed germination tests and enchytraeid worm survival and reproduction tests and the ecotoxicity of the organic wastes was investigated with a lettuce seed germination test before and after the leaching experiments.
The results of the present study proved that the environmental hazard of solid wastes and soil samples was underestimated when only the total concentrations of known key hazardous substances were analyzed. It was also found that the release of these substances should be determined in order to predict the longterm environmental impacts of solid wastes. It was also important to perform an availability test on the inorganic
wastes in order to ascertain their resistance to acid attack. The batch leaching tests performed on the organic wastes and contaminated soil samples studied showed that these methods should be used to screen the waterleachable fraction of the key organic compounds. The differences between the chemical and ecotoxicological classification emphasized the need for ecotoxicity tests to complement chemical analyses in the hazard classification of wastes. For example, fly ash was classified as nonhazardous by chemical analyses but ecotoxicity assays proved that the batch leaching test eluates of this waste had high or very high aquatic toxicity (10100). The organic wastes contained large amounts of compounds not identifiable with available chemical analyses. A more costeffective and relevant estimation of the overall environmental hazard of complex mixtures of unknown substances in solid wastes and their eluates could be made with a combined solidphase and liquidphase approach using ecotoxicity assays and TOC analyses.
Based on the present study, the European batch leaching test method (EN124572) was proposed for the combined chemical and ecotoxicological classification of substances leached out from inorganic and organic wastes and soils. Only then can ecotoxicity test results be compared with chemical analyses to improve hazard classification when selecting the best waste management alternative. The battery of toxicity tests should consist of costeffective methods that are simple to perform, in which the volume required for analyses is minimized. According to this study, the luminescent bacteria test, MetPLATE and ToxiChromo tests, RET assay and onion root elongation test were the best choice. Wheat or lettuce seed germination tests are proposed for the determination of the ecotoxicity of solid wastes. The proposed terrestrial toxicity method for oilcontaminated soils was the Enchytraeid worm (E. albidus) survival test.
This study demonstrated that environmental hazard assessment of solid wastes based only on the chemical analyses of known key hazardous substances and available regulatory values was inadequate. The results showed that the criteria for both waste classification and management could be improved by setting criteria and limit values for ecotoxicity test results. A new screening approach and criteria for the evaluation of the environmental toxicity of wastes are presented. This approach would aid environmental authorities in making decisions on waste hazard classification and help waste producers to improve their processes and minimize the environmental impacts of wastes.
Chemical classification was carried out by comparing total concentrations of key hazardous substances in the wastes studied with the limit values set for hazardous wastes, and comparing the leached amounts of the substances with the limit values proposed by the EU. Four wastes studied from the metal and forest industries contained predominantly inorganic compounds and ten from the furniture and resin industries mainly aromatic or aliphatic organic compounds. Six soil samples contaminated by petroleum products were studied in order to evaluate their environmental hazard after remediation. Various types of leaching tests were used to study the leaching profiles of key hazardous substances in four predominantly inorganic wastes. Onestage or multistage batch leaching tests were also used to study the leaching of volatile organic compounds from the organic wastes and that of petroleum products from the soil samples. The ecotoxicity of substances leached out from the wastes was studied from the eluates of batch leaching tests with different combinations of aquatic ecotoxicity tests: microbial tests, water flea and algal tests, electron transport assay (RET) and plant tests. In addition, the ecotoxicity of oilcontaminated soils was studied directly from solid materials with plant seed germination tests and enchytraeid worm survival and reproduction tests and the ecotoxicity of the organic wastes was investigated with a lettuce seed germination test before and after the leaching experiments.
The results of the present study proved that the environmental hazard of solid wastes and soil samples was underestimated when only the total concentrations of known key hazardous substances were analyzed. It was also found that the release of these substances should be determined in order to predict the longterm environmental impacts of solid wastes. It was also important to perform an availability test on the inorganic
wastes in order to ascertain their resistance to acid attack. The batch leaching tests performed on the organic wastes and contaminated soil samples studied showed that these methods should be used to screen the waterleachable fraction of the key organic compounds. The differences between the chemical and ecotoxicological classification emphasized the need for ecotoxicity tests to complement chemical analyses in the hazard classification of wastes. For example, fly ash was classified as nonhazardous by chemical analyses but ecotoxicity assays proved that the batch leaching test eluates of this waste had high or very high aquatic toxicity (10
Based on the present study, the European batch leaching test method (EN124572) was proposed for the combined chemical and ecotoxicological classification of substances leached out from inorganic and organic wastes and soils. Only then can ecotoxicity test results be compared with chemical analyses to improve hazard classification when selecting the best waste management alternative. The battery of toxicity tests should consist of costeffective methods that are simple to perform, in which the volume required for analyses is minimized. According to this study, the luminescent bacteria test, MetPLATE and ToxiChromo tests, RET assay and onion root elongation test were the best choice. Wheat or lettuce seed germination tests are proposed for the determination of the ecotoxicity of solid wastes. The proposed terrestrial toxicity method for oilcontaminated soils was the Enchytraeid worm (E. albidus) survival test.
This study demonstrated that environmental hazard assessment of solid wastes based only on the chemical analyses of known key hazardous substances and available regulatory values was inadequate. The results showed that the criteria for both waste classification and management could be improved by setting criteria and limit values for ecotoxicity test results. A new screening approach and criteria for the evaluation of the environmental toxicity of wastes are presented. This approach would aid environmental authorities in making decisions on waste hazard classification and help waste producers to improve their processes and minimize the environmental impacts of wastes.
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