Sequential Treatment of Tequila Industry Vinasses by Biopolymer-based Coagulation/Flocculation and Catalytic Ozonation

This article describes the study of the treatment of tequila industry vinasses based on the sequential application of coagulation-flocculation and heterogeneous catalytic ozonation. Coagulation-flocculation treatment used biopolymers to reduce the nondissolved organic matter and to reduce the degree of color units in effluent. Among six different substances, chitosan was the most efficient biopolymer to remove the highest chemical organic demand (COD) concentration (84.0%). The response surface technique was used to obtain the best attainable operation conditions of coagulation-flocculation process. The initial organic matter concentration, the reaction period and biopolymer concentration were selected as the independent variables. Two levels of analysis were performed: optimally and sensibility. The best reaction conditions were 3.23 × 10⁴ mg L⁻¹ of initial COD, 125.4 mg L⁻¹ of chitosan concentration, and 60.0 min of reaction. Ozonation process was performed on the effluent of coagulation-flocculation treatment. A batch reaction with 30 mg L⁻¹ of ozone in gaseous phase and a flow of 0.1 L min⁻¹ was implemented. Nickel oxide (100 mg L⁻¹) was used as the catalyst of the ozonation reaction. Twice larger COD concentration removal was obtained when the catalyst participated in the reaction compared to the so-called conventional ozonation (12.00% in conventional case vs 26.70% in catalyst presence). An ultraviolet-visible (UV-Vis) spectroscopy study was conducted to obtain a preliminary evaluation of organic compounds removal by effect of the sequential method proposed in this study. A significant total organics removal from the tequila industry wastewater (measured as the integral of UV-Vis spectrum) of 398.6 conditional units was obtained when the conventional ozonation was used after coagulation-flocculation, but that value was increased up to 1609.12 conditional units when the catalyst was inserted into the reaction.