DEPHY project: Distillery wastewater treatment through anaerobic digestion and phycoremediation-A green industrial approach

Distilleries produce on an average of 15 L of effluent per litre of alcohol which has the characteristics of BOD as 40,000-50,000 ppm and COD as 80,000-100,000 ppm. In industries, the effluent is treated by anaerobic digestion having twin benefits such as degrading the effluent to an extent of BOD 8,000-10,000 ppm, COD 29,000-35,000 ppm while producing biogas having 55% methane. 0.4 to 0.6 kg of methane is produced per kg of BOD reduced by anaerobic digestion. Effluent after anaerobic digestion is subsequently treated by aeration technique. Treatment through aeration requires high energy for treating the effluent to the standards. Now, due to water crisis, number of industries is following either reverse osmosis (RO) or multiple effect evaporation after anaerobic digestion to recycle the water. RO is employed to recover 60% of water as permeate with COD of 100 ppm. Admitting high pollutant load to the RO process, leads to higher pressure drop across the membrane, increasing its operational and maintenance cost. The pollution profile of the reject is more complicated to tackle. In case of multiple effect evaporators, 550 kcal of energy is required for evaporating 1 L of water. The performance of the evaporators will deteriorate faster with time, due to the high influent load and reducing its life cycle. Hence, it necessitates the requirement of an intermediate treatment which would help to reduce the effluent characteristics of biomethanated wash to an appreciable level and would make the further operations less energy intensive. The major reason for high BOD, COD of effluent is due to the presence of colored compounds such as melanoidin. This review aims at degrading possibility of melanoidin using phycoremediation as an intermediate step between anaerobic digestion and aeration. The biomass thus generated by growing microalgae, will be useful for producing by-products.