Treatment of vinasse from tequila production using polyglutamic acid.

Vinasse, the wastewater from ethanol distillation, is characterised by high levels of organic and inorganic matter, high exit process temperature (ca. 90 °C) and low pH (3.0–4.5). In this study, the treatment of tequila vinasse was achieved by a flocculation–coagulation process using poly-γ-glutamic acid (PGA). Results showed that the use of PGA (250–300 ppm) combined with sodium hypochlorite and sand filtration managed to remove about 70% of the turbidity and reduced chemical oxygen demand (COD) by 79.5% with the extra benefit of colour removal. PGA showed its best flocculating activity at pH 2.5–3.5 and a temperature of 30–55 °C. Such a treatment may be a solution for small tequila companies for which other solutions to deal with their vinasse may not be economically affordable.