Approved Abstracts

Feasibility in reducing the coloration of different textile effluents by Microcystis aeruginosa

Author(s): Lira, V.S.; Da Silva, J.; Moreira, I.C.; Ramos, P.; Bagatini, I.L.; Fracácio, R.;
Presenter: Renata Fracacio Francisco

The increasing scarcity of water sources as well as the mandatory compliance with
legal requirements, end up demanding alternatives for the treatment of effluents. Among
the countless sectors that generate effluents with the potential for toxicity, textiles stand
out. Thus, this work aimed to evaluate the potential discoloration of different textile
effluents by a species of resistant and dominant cyanobacteria in several ecosystems and
not yet reported in the literature for that purpose, Microcystis aeruginosa. An additional
approach of toxic effects of these cyanobacteria on the survival of Danio rerio larvae
exposed to ecotoxicological tests was used, before and after the realized treatment. The
bioremediation experiments occurred with samples of raw effluents and too were
diluted by 50%. Lethality tests with larvae for the jeans factory effluent resulted in a
168h-LC15 = 7.19% and 168h-CVest = 2.16 (v/v) of the raw effluent, and therefore a
marked potential for toxicity in both survival and growth for the organism. It was
observed that 25; 50; 75 and 100% of the jeans factory is raw effluent caused 100%
mortality in less than 48 hours of exposure. Similarly, the carpet factory raw effluent
indicated a 168h-LC15 = 11.88% and 168h-CVest = 3.56% of the raw effluent. It is
worth mentioning that the concentrations of copper, nitrogen, and especially sodium in
the raw effluent exceeded the LC15 values for the larvae, and therefore, by themselves,
they have the potential for ecotoxicity. The LC15 and CVest obtained in this study for
both effluents ratify the potential ecotoxicity of untreated textile effluents for aquatic
biota. After 25 days of bioremediation, the discoloration was not accentuated and the
cyanobacterium Microcystis aeruginosa did not develop in the effluents. It was
observed that the color removal rate by M. aeruginosa, with an initial inoculum of 8.64

x 10 3 cel/mL, was lower when compared to conventional methods (aerobic-anaerobic
treatments). In the present study, there was greater color removal of the effluent from
the aerated jeans factory when compared to the effluent with M. aeruginosa, unlike the
effluent from the carpet factory. Ecotoxicological tests with 100% of the carpet factory
effluent revealed a persisted ecotoxicity to the larvae, with and without the presence of
M. aeruginosa. In the bioremediation effluent of the jeans factory, there was
ecotoxicity. The cyanobacteria did not enhance the ecotoxicity of the effluents. Textile
effluents, due to their high complexity, are not easily degraded, and in the present study,
their discoloration was not satisfactory. The ecotoxicity was reduced probably due to
the natural degradation of chemical agents. It was not possible to associate discoloration
and reduced ecotoxicity by M. aeruginosa.

Keywords: cyanobacteria,; dyes,; Danio rerio




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