Ecotoxicological Evaluation and Treatment of a Denim-Laundry Wastewater
2022
Méndez-Hernández, Jazmín Edith | Ramírez-Vives, Florina | Sobrino-Figueroa, Alma Socorro | Garza-López, Paul Misael | Loera, Octavio
Several laccase-based products have been launched on the market over the years. However, there is little information about their toxicity and/or the toxicity of their residues. We evaluated the toxicity of a simulated denim-laundry wastewater containing Biolite BSN, a laccase-based product used for denim bleaching. The evaluation included a viability test with Saccharomyces cerevisiae, a phytotoxicity test with Sorghum vulgare, and a toxicity test with Daphnia magna. The viability of S. cerevisiae was reduced to 40%. The radicle and plumule growth of S. vulgare was reduced to 62 and 66%, respectively. The CL₅₀ for D. magna was 29.7%, which classified this water as toxic (according to the percent rank method). Biolite BSN was identified as the main cause of the toxic effects; furthermore, the chemical oxygen demand (COD) of the wastewater was significantly high (3346.2 mg/L), and more than 90% of the COD corresponded to Biolite BSN. The anaerobic biodegradability tests showed that the denim-laundry wastewater could be treated anaerobically; therefore, it was treated in an upflow anaerobic sludge blanket (UASB) reactor. The treatment reduced the toxicity and COD in 50 and 77%, respectively, and a methane yield of 311.1 mL CH₄/g of CODᵣₑₘₒᵥₑd was obtained. Based on these results, we recommend to analyze the toxicity of all textile chemicals, regardless of whether they are enzyme-based products. A UASB reactor can be used as the first treatment stage for similar effluents in order to reduce the COD and the toxicity and recover methane as an added benefit.
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