Toxicity determination of leachate from municipal solid waste using biological indicators

Final disposal of Municipal Solid Wastes - MSW in landfills is still well accepted and used for its economic advantages; however, this type of disposal is the responsible of greenhouse gas emission and leachate production. The leachate resulting in landfills comprises a very complex composition of organic, inorganic and heavy metal content, therefore, to determine the strategies to balance the potential toxic effect of this substances in the environment it is necessary an appropriated characterization. The current regulatory approach considers the physic-chemical characterization and the toxicological assessment for this type of liquid wastes, as well. The main objective of this work was to determine the influence of the leachate age over the physic-chemical properties and its toxicity using Daphnia pulex as indicator organism, in acute and static test for 48h. Leachates studied where sampled from different aged landfills: Young leachate (JL) for less than 5 years, Intermediate aged leachate (IL) between 5-10 years and Mature Leachate (ML) for more than 15 years. It was found that physic-chemical parameters such as COD, conductivity and ammonia nitrogen are inversely proportional to the leachate age. The Daphnia pulex toxicity essays showed a less toxicity for the oldest leachate, with 83.1, 47.7 and 27.7 TU (toxic units) of LC50 for the JL, IL and ML respectively.