APPLICATION OF MEMBRANE AND ELECTROCHEMICAL PROCESSES FOR DISTILLERY SPENT WASH TREATMENT AND POTASH RECOVERY

Abstract

Distillery Spent Wash generated during the fermentation step in ethanol production is characterised by low pH, unpleasant odour, dark brown colour pigments named melanoidins (product of Maillard’s reaction), and a high percentage of dissolved organics (52,000–58,000 mg/L BOD; 92,600-1,00,000 mg/L COD) and inorganic matter (1,660– 4,200 mg/L form of nitrogen, 225–3,038 mg/L phosphorus, and 9,600–17,475 mg/L potassium, etc.). The presence of proteins, polysaccharides, lignin, lactic acid, glycerol, resin, and waxes, along with a complex mixture of recalcitrant organic acids, is mainly attributed to the high organic content of the spent wash. These characteristics have led to severe environmental concerns, including the eutrophication of bays, lakes, and inland seas. Moreover, in response to stricter environmental regulations, distilleries are compelled to enhance their existing treatment methods and explore alternative approaches to manage spent wash. Characterisation of spentwash shows a high concentration of organic and inorganic contaminants with a high potassium concentration. In general, deploying various membrane systems in different configurations has demonstrated promising results. However, an opportunity to recover energy, nutrients, and water reclamation has still not been fully realised, considering the spent wash’s high organic and inorganic content. Around 88% of the molasses passes into the spentwash, containing 5 to 8 g/L of potassium that passes on even after anaerobic digestion. Given the above, it is necessary to explore alternative integrated viz. membrane and electrochemical hybrid process approaches towards an efficient separation of the complex in organic and inorganic streams for sustainable waste management and resource recovery in the form of potash.