This paper describes the use of aquatic ecotoxicological tests, in combination with chemical analysis, in the evaluation of the application of low-cost pine bark sorbent, a by-product of the forestry industry, to treat low-strength landfill leachate. Initially, leaching batch tests with the untreated filter material were carried out to investigate the leaching properties of the filter material and the safety of using the material for water treatment. The test showed that leaching of metals, such as Cu, occurs, although at levels below the US EPA MCL limits. The DOC concentration in the leachate from pine bark was 69 mg/l (SD = 0.62). Phenols were measured to 4.4 mg/l (SD=0.35), which represents 7% of the DOC. 24 h and 48 h EC50 values for acute toxicity of leachates without pH adjustment to Daphnia magna were determined to 38% and 42% leachate concentration, respectively. All the test organisms were immobilised in the batch test with 100 % of the leachate concentration. The pH adjusted leachate samples showed no toxicity to Daphnia magna during 24 h or 48 h exposure. Subsequently, a tentative study with serial batch leaching tests was performed to further investigate the extent and duration of the leaching of organic material from the unused filter material. The preliminary results from the serial batch leaching showed that pH of the leachates decreased to below 5 even after three successive rounds of leaching of the pine bark. Desorption of DOC was not reduced by serial leaching of the filter material and did not appear to correlate with the observed decrease in toxicity after sequential leaching rounds. The toxicity of leachates from the untreated, unused filter material decreases after the first initial flush of water through the filter. There is a trend of reduced toxicity after each successive round of leaching for the 48 hour exposure of Daphnia magna to the leachates. All the test organisms were immobilised in the batch test with 100 % of the leachate concentration. Future research will focus on further investigation of the initial leaching duration and on chemical characterization of the leachate, with an emphasis on organic compounds.