Sugarcane Industry Wastewaters Treatment

Abstract

The sugarcane industry, and particularly one that produces distilled potable products besides sugar (sucrose), generates wastewater with a high content of organic and inorganic compounds that are difficult and costly to remove. Particularly those from ethanol production, known as vinasses (the fermented musts are known as wines, from Latin vinum ), contain from 60 to 150 g COD/L. Compared with household sewage, that has 400 to 800 mg COD/L, vinasses are about 75 to 375 times more polluted. Vinasses contain important amounts of organic chemical substances from the raw materials used during fermentation, such as undegraded sugars, polyphenols, phenols, inorganic ions such as sulfates, and dead yeast. In Mexico, for example, each liter of fermented and distilled ethyl acohol implies the generation of vinasses that may reach up to 12 liters. Most of these vinasses, to date, are discharged to receiving bodies (soil, surface water sources) without any treatment or only with partial depuration. The use of thermophilic anaerobic systems stabilize and recycle these liquid residues from distillation of fermented musts that produce methane gas and may be used within the plants to generate steam for the distillation towers, is a feasible technology that may be easily adapted to the conditions in distilleries in most tropical countries where sugarcane grows. Then, they may use an aerobic treatment whose microbial biomass can be used in fish feedlots. In tropical countries, a crustacean such as river shrimp can be “cultivated” using fish by‐products, and its cephalothorax can be used to produce chitin, a very high value natural polymer, and a carotenoprotein complex to be added to fish pellets to increase their antioxidant content and the final fish flesh organoleptic quality that gives it a pink salmon color. Wastewaters that contain mainly acid and caustic compounds can be evaporated using solar energy and the resulting salts recycled to the companies that provide these chemicals.