Comparative ecotoxicological evaluation of tannin coagulants from black wattle and ferrous aluminum sulfate in the treatment of slaughterhouse effluent

Ecotoxicological assessments are crucial for environmental monitoring as they can pre-dict the adverse effects of ecotoxins, such as coagulants, on the ecosystems using contamination bioindicators. This study evaluated the ecotoxicity of two types of coagulants, an inorganic coagulant, ferrous aluminum sulfate (SF), and a biocoagulant based on tannins extracted from black wattle, used in the treatment of cattle slaughterhouse effluents. The planaria Girardia tigrina, which is used as a bioindicator of toxicity in freshwater ecosystems, was used as the test organism for this study. To select the appropriate tannin coagulant for the effluent under study, two types of biocoagulants were investigated: Tanfloc SG (SG) and Tanfloc MTH (MTH), with SG coagulant showing better performance (98.5 % turbidity removal). In the ecotoxicological test, SG and SF coagulants were compared. Both the tannin-based coagulant SG and the inorganic SF were effi-cient for the treatment of the evaluated effluent, yet their lethal concentrations (LC50 - 96h) with regard to G. tigrina was 32.24 % and 42.24 %, respectively. Thus, our results suggest that the effluent treated with the tannin-based coagulant SG showed greater toxicity to G. tigrina than the inorganic coagulant ferrous aluminum sulfate.