Evaluation of Mezcal Distillery Vinasse at Various Concentrations as a Culturing Medium for Stigeoclonium Nanum

Abstract

Vinasse is an effluent generated during the distillation process of mezcal and other alcoholic beverages. This substance typically shows an acidic pH and a high concentration of organic matter, causing a potentially polluting byproduct if not subjected to appropriate treatment and disposal methods. However, used efficiently, the high organic load within this effluent can be a rich source of soluble carbon and other organic nutrients, such as nitrogen and phosphorus, for microalgae growth. This study evaluated the tolerance of Stigeoclonium nanum to mezcal vinasse, using dilutions of 10, 20, 30, and 40 %, using complementary inoculum fractions in BG11 mineral medium over an eleven-day kinetic period. Daily determinations of photosynthetic pigments, nitrate nitrogen, and total phosphorus were made, along with the determination of Chemical Oxygen Demand (COD) at the beginning and end of the kinetic. The results revealed optimal growth with a higher production of photosynthetic pigments (compared to the control kinetic in mineral medium) at the 20 % dilution. The results obtained for this dilution were 18 mg L-1 of chlorophyll total production at the end of the kinetic period; additionally, a reduction of nitrate nitrogen on the effluent of 97.23 %, equivalent to 22.77 mg L-1, and a decrease of total phosphorus by 88.33 %, corresponding to 1.74 mg L-1. There was also a decrease of COD by 757 mg L-1, constituting 56.36 % of the total content in the effluent. When contaminants persist in the water with values higher than the allowed limits, it may cause some harmful effects on the environment. Microalgae exhibit remarkable adaptability and have the potential of consuming high amounts of nitrogen and phosphorus from wastewater treating pollutants from it to release them into the environment in compounds with less or no toxicity; thus, avoiding the risk of eutrophication of the water bodies and reducing the toxicity to human health. Utilizing effluents with high organic loads, such as vinasse, presents challenges. Therefore, this study provides a foundation for developing a culturing medium that ensures microalgae biomass growth and offers a phytoremediation alternative for treating industrial effluents.