Abstract
Tequila vinasses represent an acidic, highly concentrated pollutant effluent generated during the distillation step of Tequila production. Although acidogenesis of Tequila vinasses has been reported for some reactor configurations, a characterization of the bacteria present during this metabolic process is lacking in the literature. Hydraulic retention times (HRT) between 36 and 6 h and organic loading rates (OLR) from 5 to 30 g COD L−1 d−1 were assessed in a UASB reactor fed with Tequila vinasses. Results showed that OLR excerted a stronger effect (p ≤ 0.0001) on parameters such as gas production rate, pH, and acidity than HRT. While it was clear that shorter HRT were related to higher volatile fatty acid production levels. Figures above 2 Lgas Lreactor−1 d−1 (where “gas” could be a mixture of methane and hydrogen) were attained only with an OLR as high as 30 g COD L−1 d−1. Bacterial identification of a sludge sample at the end of the experiment revealed that acid-tolerant microorganisms that remained in the reactor were exclusively affiliated to the Clostridium genera, being the first report of organisms identification for Tequila vinasses acidogenesis. These findings are relevant to the field of biotechnology since acidogenesis of Tequila vinasses using identified and studied microorganism abilities (i.e. Clostridium strains) presents the opportunity of optimizing processes intended for different metabolites production (butanol, volatile fatty acids, hydrogen, solvents).
Highlights
Total production of the well known mexican spirit called Tequila was around 242.4 million liters in 2014 (CRT 2015b)
Reactor was started to operate under a Hydraulic reten‐ tion times (HRT) of 36 h and an organic loading rate of 5 g chemical organic demand (COD) L−1d−1
Results showed a COD removal percentage of 70% by the end of phase I (Fig. 1). The combination of both HRT reduction from 36 to 24 h together with organic loading rates (OLR) increase from 5 to 15 g COD L−1d−1 led to a sharp decrease in both pH and removed COD
Summary
Total production of the well known mexican spirit called Tequila was around 242.4 million liters in 2014 (CRT 2015b). With seasonal variations in the past decades, Tequila production in the last ten years has nearly doubled (CNIT 2015). This economic activity is very important for a mexican region comprising 181 municipalities that retain the protected apellation of origin for this representative beverage (CRT 2015a). Few tequila producers have invested in acquiring wastewater treatment plants and installed facilities for reducing the environmental impact of these effluents, being the anaerobic digestion (AD) process the most successful core technology for removing high levels of organic matter together with the production of bioenergy in the form of biogas (Buitrón et al 2014b).
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