CONICET | Buscador de Institutos y Recursos Humanos

The textile industry is characterized by generating large volumes of highly colored and saline wastewater, which also present a great variety of chemical pollutants. The pigmentation of the wastewater blocks the solar penetration in water bodies, affecting the photosyntheticactivity and reducing the dissolved oxygen, which is necessary for all forms of aquatic life. In this industry, the azo dyes are the most used because of their excellent fixation, durability, photolytic stability and resistance against microbial degradation. However, some of the azo dyes have been reported as carcinogenic, mutagenic and toxic. Different fish species are widely used as experimental biological models in toxicity tests both for azo dyes and textile wastewater. The main objective of this work was to evaluate the toxicity of the azo dyes Naphthol Blue-Black and Methyl Orange, and a real textile wastewater obtained from a local textile industry (San Luis, Argentina), against two widely used fish species for biological assays: Danio rerio and Poecilia reticulata. Juvenile (10-15 days) and adult specimens (6 months) of D. rerio and P. reticulata were exposed to 500 µg mL-1 of the azo dyes, individual and combined, during 96 h. In addition, theembryotoxicity was evaluated on newly fertilized D. rerio eggs, analyzing the hatching time, possible deformations and post-hatching survival. In this case, increasing concentrations from 25 to 100 µg mL-1 were evaluated. Finally, the same assays mentioned before were carried out employing a real textile wastewater. The pure effluent and serial dilutions were evaluated. All the assays were carried out in triplicate, with three individuals in all the selected conditions. The tests were repeated at least three times. The arithmetic means were evaluated through comparative statistics (ANOVA), p=0.05; evaluating the homogeneity of variance to select the statistic best adapted to the data collected. The software IBM SPSS Statistics v24 was applied to statistical analyses. The results obtained in the present work for the acute toxicity tests showed that the evaluated azo dyes (even at doses up to 500 µg mL-1) and the real textile wastewater (even in its pure state) did not produce mortality in either of the two species. Similar results were obtained in the embryotoxicity tests in D. rerio eggs.Despite the azo dyes and the textile wastewater do not show acute toxicity in the evaluated species, the pigmentation of the wastewater represents a serious threat to the ecosystem. Therefore, the decolorization of effluents using biocatalysts appears as an eco-friendly alternative to remediate industrial wastewaters. This opens doors to assess the toxicity of the bioproducts to ensure a safety discharge to the environment.