Complete information on Distillery

There are 285 distilleries which are in operation in India with a installed capacity of about 2.7 billion litre alcohol per annum which amounts to generation of nearly 40 million litres of spent wash in one year.

Wastewaters discharged by distillery producing industrial alcohol from sugarcane, molasses poses disposal problem due to their high BOD, COD, colour and odour. As per estimate the daily effluent generation from distilleries is about 30 million litres. The spent wash is highly organic in nature with BOD value ranging between 40,000 to 50,000 mgand1.

The wastes results from condense water, carbon dioxide gas plant wastewater and yeast sludge. Condenser water and carbon dioxide gas plant waste water are relatively pure and do not contain appreciable amount of pollution and as such pose no treatment problems.

The quantity of process water in distilleries varies with an average value of 130 litres per litre of alcohol produced. The generation of spent wash also varies with the production of alcohol. The volume of spent wash generated is about 15 litres for each litre of alcohol produced. The waste is hot, colored and acidic, containing very high concentration of organic matter. The distilleries usually discharge waste waters as spent wash and condensate water which together form final effluent.

The general practice followed in many countries for the disposal of distillery effluent is to let this waste water into sea without treatment or partial treatment. In some places it is being treated and disposed off along with domestic wastewater. In India, most of the distilleries are situated far away from the coastal regions and majority of the places where, distilleries are located do not have any facility for the collection and disposal of domestic wastes. Thus, it is essential to give treatment to the distillery wastes. The following methods have been suggested.

1. Direct use after neutralization and dilution for irrigation purposes.

2. Evaporation and incineration of spent wash for the recovery of potassium salt.

3. Ammonification process.

4. Manufacture of yeast from spent wash.

5. Anaerobic treatment.

The treatment of distillery spent wash by anaerobic methods has been practiced for a long time. The treatment with anaerobic lagoons and conventional digesters are applied to some extent in the field. With the development of processes with longer biological solids retention time approach, the present day research has been directed in the application of these processes.

Because of the geographical location of distilleries and the non-existence of proper collection and treatment systems for domestic wastewater in the neighboring towns, the distilleries in India are forced to dispose off their effluents either into inland waters or on to the land. The Indian Standard requires that BOD and COD of the treated effluent should be brought down to 30 and 250 mg. per litre for disposal into land water.

Whereas the respective value for disposal on land should be less than 100 and 250 mg. per litre. As none of the treatment methods achieve this target, further treatment or dilution before final disposal is considered essential. However, because of the large quantity of spent wash water and relatively high values of BOD and COD, in an aerobically treated effluent, it is almost impossible to meet the dilution water requirements. There are few studies which attempt further reduction in BOD and COD values of an aerobically treated spent wash water.

The distillery wastes are presently being recycled to produce methane for energy needs by many distilleries. The post meth nation effluents still have considerable organic and salt load. Mostly this waste water is disposed into the streams or rivers and imposes considerable threat to the fragile aquatic ecosystems. An accidental discharge of the distillery effluents into river Gomati at Luck now caused severe damage to the aquatic environment and in turn disrupted the drinking water supply of the city.

Thus suitable mitigation measures to check the ill effects of distillery effluents become imperative. The organic nature of the effluent and its high nutrient content especially potassium and sulphur provides scope for its use for irrigating agricultural crops. With this the available nutrients present in the effluent can be recycled into crop biomass without causing any damage at the soil environment.

In view of the tremendous polluting potential of distillery waste for fresh waters and growing scarcity of the water resources, land application may be a suitable option and alternative for chemical and biological treatment.