Biological testing methods for the ecotoxicological characterisation of waste

Based on the recommendations of CEN guideline 14735, an international ring test was organised by BAM, FH Giessen-Friedberg and ECT. In total, 67 laboratories from 15 countries participated in this ring test. It was performed with three representative waste types: an ash from an incineration plant mainly contaminated with heavy metals, a soil containing high concentrations of organic contaminants, and a preserved wood waste contaminated with copper and other heavy metals. Samples were prepared (e.g. inter alia dried, sieved and homogenised) and distributed. Parallel to the biological testing, the eluates and solid samples were chemically characterised. The basic test battery used in the ring test consisted of three aquatic tests (algae, Daphnia acute and Microtox test) and three terrestrial tests (earthworm acute and plant test with two species, oat and rape). Further data were generated using ten additional tests: five aquatic (including a genotoxicity test) and five terrestrial tests. Almost all tests were performed according to ISO guidelines, providing EC50 values. Besides a high number of reference test data, 634 data sets were produced in the basic test battery and 204 data sets in the additional tests. Only few data sets were not acceptable (e.g. due to lack of reference data) and even less results were identified as statistical or biological outliers. Independently which test system is considered, the soil containing high concentrations of organic contaminants always caused the lowest effects and the preserved wood waste contaminated with copper and other heavy metals was most toxic, while the EC50 values of the ash from an incineration plant mainly contaminated with heavy metals showed an intermediate toxicity. Among the aquatic tests, daphnids and one algal species were the most sensitive ones, while plants were always more sensitive than earthworms for the solid waste samples. Based on the test results from additional tests, proposals were made for the modification of the existing basic test battery. In particular, the earthworm acute test could be replaced by another soil invertebrate test with higher sensitivity. A comparison of the ring test results with literature data published so far revealed a good agreement. The results of this ring test confirm that a combination of a battery of biological tests and chemical residue analysis is needed for an ecotoxicological characterisation of wastes. With small modifications, the basic test battery is considered to be suitable for the hazard and risk assessment of wastes.