Distillery wastewater: bioremediation approaches

The alcohol distilleries are growing extensively worldwide due to widespread industrial applications of alcohol such as in chemicals, pharmaceuticals, cosmetics, beverages, food and perfumery industry, etc. The industrial production of ethanol by fermentation results in the discharge of large quantities of high-strength liquid wastes. Distillery wastewater is one of the most polluted waste products to dispose because of the low pH, high temperature, dark brown colour, high ash content and high percentage of dissolved organic and inorganic matter with high biochemical oxygen demand (BOD) and chemical oxygen demand (COD) values. Its characteristics are depending on the feed stock and various aspects of ethanol production process. Spent wash polluted the water bodies into ways; first, the highly colored nature which can block out sunlight, thus reducing oxygenation of the water by photosynthesis and hence becomes detrimental to aquatic life. Second, it has a high pollution load which would result in eutrophication of contaminated water sources. Distillery wastewater, without any treatment can result in depletion of dissolved oxygen in the receiving water streams and poses serious threat to the aquatic flora and fauna. This review presents an account of the problems associated with distillery wastewater and a detailed study of existing biological treatment approaches. The role of various microorganisms and their enzymes in the wastewater treatment has been discussed to develop a better understanding of the phenomenon.