Distillieries - Environmental Clearance

Distilleriesc) Source of fertilizer ingredientsFermenter sludge, after drying, can be used as fertilizer for some crops. Use of driedfermenter sludge as fertilizer is a common practice in distilleries treating the spent washstream in anaerobic lagoons located mostly in the western part of India. Disposal offermenter sludge as a source of fertilizer ingredients is also practised in distilleriesabroad.As reported during a survey, the distilleries that use fermenter sludge as fertilizer dry thesludge either in open pit (sun drying) or in sludge drying beds. However, a large quantityof mineral matter present in the fermenter sludge can have some detrimental action of thecrops rather than the fertility value in dried yeast and potassium salts. This matter needsto be carefully studied before using the fermenter sludge as fertilizer.3.10.2 Spent washAs mentioned earlier, spent wash is the principal pollutant stream from distilleriesdischarged from the analyzer column. Spent wash stream is a continuous process effluentand its volume is about 17 kL per kL of RS. One distinct feature of spent wash is thehigh content of potassium salts which obviously originates from the cane sugar as it isgenerally very rich in potash content. The spent wash which generally contains about8% solids can be evaporated and then subjected to incineration to recover the mineralmatters present in spent wash. The ash (mineral matter) thus recovered can be furtherprocessed to potassium salt as potassium sulphate which is a potent fertilizer commonlyused as one of the ingredients of mixed fertilizer the world over. Apart from this, somedistilleries use evaporation of spent wash and spray drying.The CPCB has identified different technologies for spent wash treatment and has alsodeveloped guidelines for some of these technologies, which are as follows.1. Anaerobic digestion followed by two stage aeration and ferti-irrigation2. Anaerobic digestion followed by controlled land application3. Raw spent wash composting4. Anaerobic digestion followed by Composting if filler material is adequate. If fillermaterial is not adequate, anaerobic digestion followed by reboiler/reverse osmosis(RO)/ evapouration to reduce volume of the effluent and Composting/Drying5. Raw Spent wash Concentration and Incineration in BoilerThe treatment based on the first three options discussed above is being discontinued bythe MoEF as these technologies are found to have inherent limitations resulting ingroundwater and soil pollution. It has also been suggested that the distilleries which areadopting these technologies shall switchover to the new technologies in a phased manner.For new or expansion of the existing distillery capacities, environmental clearances areonly given based on the technologies discussed below:1) Anaerobic digestion followed by two stage aeration and ferti-irrigationDistilleries attached with Sugar units can adopt anaerobic digestion of spent washfollowed by composting if sufficient filler material is available for composting. In casethe filler material is not adequate, the effluent quantity shall be reduced by Reboiler/evapouration/RO to match the quantity of press mud. The concentrated effluent can bedried in spray dryers as powder which can be sold as a fertilizer. The anaerobic digestionfollowed by evapouration in Multiple Effect Evapourators (MEE) to reduce the volume ofTGM for Distillery Industry 3-38 August 2010