Electrocoagulation and Coagulation of Distillery Spent Wash Effluent EC of Distillery Spent Wash 6/10/2018 Vinita Khandegar and Anil. K. Saroha* Department of Chemical Engineering Indian Institute of Technology Delhi, India Textile industries are one of the most polluting industries in terms of the volume and complexity of its effluents discharge. The dyeing and finishing operations in textile industries contribute a major share to wastewater generation. So that I have taken interest in treatment of textile industry effluent using electrocoagulation. 15 December 2012

Distillery Industry Demand for alcohol is likely to increase India is the fourth largest producer of ethanol in the world and the second largest in Asia. India produces about 3.25 billion litres of alcohol annually. Applications of ethanol Potable liquor (spirit and beverage) Industrial alcohol (drugs, rubber, pesticides, solvents, pharmaceutical and flavouring) Demand for alcohol is likely to increase Chauhan, M.S., et al., International Conference on Future Environment and Energy, Singapoore,, 119-123, (2012).

Water Pollution Problems in Distillery Industry The distilleries are listed at the top in the “Red Category” industries having a high polluting potential. There are 319 distilleries in India producing 3.25 billion litres of alcohol and generating 40 billion litres of spentwash annually Tewari, P.K. et al., Resour. Conserv. Recycl., 52, 351-367 (2007). Uppal, J., Proceedings of the Indo-EU workshop on Promoting Efficient Water use in Agro-based Industries, New Delhi, 12-15, (2004). Selvamurugan, M., et al., J. Bio. Sci. 11(6), 417-422, (2011).

Generation of effluent from Distillery Industry Spentwash From Distillation Column Spent Lees From Analyser Column Other wastewaters like fermenter washings, fermenter cooling, floor washings, spillage and cooling. 10-15 litres of spentwash is generated for every litre of alcohol produced

Potential polluting agent because Spentwash Waste water (spent wash) generated by distilleries during the distillation and fermentation of molasses to ethyl alcohol using specific strains of yeast. A dark brown coloured liquid Containing residual nutrients from sugarcane and yeast cells Does not contain any heavy metals or other toxic residues Potential polluting agent because

Characteristics of distillery spentwash Parameters Values of distillery effluent pH 3.0–4.5 BOD5 (mg/L) 50,000–60,000 COD (mg/L) 110,000–190,000 Total solid (TS) (mg/L) Total volatile solid (TVS) (mg/L) 80,000–120,000 Total suspended solid (TSS) (mg/L) 13,000–15,000 Total dissolved solids (TDS) (mg/L) 90,000–150,000 Chlorides (mg/L) 8000–8500 Phenols (mg/L) 8000–10,000 Sulphate (mg/L) 7500–9000 Phosphate (mg/L) 2500–2700 Total nitrogen (mg/L) 5000–7000 Zero Discharge.. A challenge..?

Proposed combination for Distillery spent wash treatment BDS Reject Sludge Biomethanation Distillery Effluent (DSW) Very High COD Acidic pH CH4 BDS Permeate 50-60 % COD reduced Alkaline pH Permeate Electrocoagulation Reject Sludge Biocomposting

Advantages of EC Limitations of EC Generate less quantity of sludge Avoids the use of chemicals Floatation for oily and grease contaminants Less maintenance is required. Limitations of EC The sacrificial anodes need to be replaced periodically. Conductivity is required in solution Passivation on the electrodes The cost of operating EC may be high in those areas where the cost of electricity is high.

Applications of EC Type of waste Type of Industry Oxygen-consuming Breweries, Dairies, Distillers, Packaging houses, Pulp and Paper, Tanneries, Textiles High Suspended Solids Breweries, Coal washeries, Iron and Steel Industries, Distillers, Pulp and Paper mills, Palm oil mills High dissolved solids Chemical plants, Tanneries, Water softening Oily and grease Laundries, Metal finishing, Oil fields, Petroleum refineries, Tanneries, Palm oil mills Coloured Pulp and Paper mills, Tanneries, Textile dyehouses, Palm oil mills, Hospital operation theatre wastewater High acid Chemical plants, Coal mines, Iron and Steel, Sulfite pulp High alkaline Chemical plants, Laundries, Tanneries, Textile finishing mills High Temperature Bottle washing plants, Laundries, Power plant, Textile Heavy Metals Electroplating, Pulp and Paper mills, Tanneries, Textile

Coagulation and Electrocoagulation A clumping of particles in water and wastewater to settle out impurities; it is often induced by coagulants such as lime, alum, and iron salts. Electrocoagulation The coagulant is generated by electrolytic oxidation of an appropriate anode material

Reactions For Aluminum Electrodes Oxidation reaction takes place at the anode Al(s) → Al3+ (aq) + 3e- Reduction reaction takes place at the cathode 3 H2O + 3e- → (3/2) H2 + 3 OH- Overall reaction during electrolysis Al 3+→ Al (OH) n (3−n) → Al2 (OH)24+ → Al3 (OH)45+→ Al13complex→ Al (OH)3 For Iron Electrodes Oxidation reaction takes place at the anode Fe(s) → Fe(aq)2+ + 2 e- Fe(s) → Fe(aq)3+ + 3 e- Reduction reaction takes place at the cathode 2 H2O + 2 e- → H2(g) + 2 OH- 3H2O + 3e- → (3/2) H2 + 3 OH- Overall reaction during electrolysis Fe(aq)2+ + 2 OH- → Fe(OH)2(s) Fe(aq)3++ 3 OH- → Fe(OH)3(s)

Chemical oxygen demand Measure of oxygen equivalent of the organic matter content of the sample that is susceptible to oxidation by a strong chemical oxidant (acid + heat) COD test results are used for monitoring and control of discharges, and for assessing treatment plant performance. Expressed in mg/l or ppm Potassium dichromate, a strong oxidizing agent is used under acidic conditions to find the amount of organic compound in waste water sample. Acidity is usually achieved by the addition of sulphuric acid. The stoichiometry of the reaction between dichromate and organic matter is:

COD TEST cont…. The amount of Cr3+ is determined after oxidization is complete, and is used as an indirect measure of the organic contents of the water sample To do so, the excess potassium dichromate is titrated with ferrous ammonium sulphate (FAS) until all of the excess oxidizing agent has been reduced to Cr3+ Calculation                                                       (A – B) ×M × 8000                      COD as mg O2/L =       mL sample where:        A = mL FAS used for blank,       B = mL FAS used for sample,      M = molarity of FAS, and 8000 = milliequivalent weight of oxygen × 1000 mL/L.

Characterization of distillery spent wash after biomethanation process (BDS) Parameter Before EC After EC pH 8.2 9.3 Chemical oxygen demand (mg/L) 44000 420 Color Dark brown Light brown Total dissolved solids (mg/L) 52410 100 Conductivity (mS/cm) 29.6 12 Salinity (mg/L) 22200 240

Conclusions Electrocoagulation can be a suitable treatment option after Biomethanation of distillery effluent. 99% COD removal efficiency was obtained at an electrolysis time of 2 hr by Al-Al electrodes. The COD removal efficiency obtained by electrocoagulation is much higher as compared to chemical coagulation technique. The maximum COD of 22 % was obtained at a pH of 8.2 with a coagulant dose of 5 g/300 mL of BDS solution.

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