The use of ecotoxicological bioassays in hazardous waste management and the water treatment industry is growing in order to meet increasingly stringent legislative requirements. Ecotoxicological tests are particularly useful for assessing the safety of samples with a complex contaminant matrix, as interactive effects between contaminants, which may affect sample toxicity, can go undetected if chemical analyses alone are used in the assessment process. By combining a wide range of tests it is possible to assess non-specific acute and chronic effects, as well as specific toxic effects such as genotoxicity, in vertebrates and invertebrates and in aquatic and terrestrial organisms over several trophic levels. Ecotoxicological tests are less commonly used during method and process development, where they may be used as a rapid and cost-effective way to evaluate performance and safety. This paper describes current and future work with a battery of ecotoxicological bioassays evaluating the use of a pine bark sorbent for treating landfill leachate and polluted process water. The results presented in the paper are from the first phase of the ecotoxicological evaluation of the filter, where the leaching properties of the filter material itself were investigated. Batch leaching tests were performed to determine the release of several metals, dissolved organic carbon (DOC) and phenol. Toxicity of the leachate to Daphnia magna was measured in acute toxicity tests, with and without pH adjustment of the leachate. To determine the duration and extent of the initial desorption of organic material from the pine bark filter serial batch leaching experiments were carried out. The change in toxicity of the leachates to Daphnia magna was assessed in acute toxicity tests.