Biomethanation Process for Distillery Spent Wash Treatment

In this article discuss about concept and process description of Biomethanation system suitable for Distillery spent wash treatment.

Biomethanation Technology for Treatment of Distillery Effluent

Contents

1 Biomethanation Technology for Treatment of Distillery Effluent
2 Bio-methanation Process Description:
3 Characteristics shown by spent wash after Bio gas production

Introduction:

The distillery effluent is known as spent wash and it is a highly concentrated liquid with a high organic and inorganic content. In Distillery industry spent wash treatment and disposal is one of the major issue.

Distillery effluent is having considerable organic matter which can be bio degradable. In the process of bio methanation ( anaerobic digestion ) , the bio degradable organic matter are getting converted into biogas , thus reducing the BOD level to 80 to 90% and COD level 60% to 75 %.

General Characteristics of Spent Wash in Distillery: The Spent wash parameter may be vary according to fermentation process follows in Distillery like batch, Fed batch and continuous process.

Sr.No.	Parameter	Batch process	Fed batch process	Bio-still process
1	Volume of spent wash generation per liter of alcohol	14 – 16	10 – 11	7 – 9
2	Colour	Dark brown	Dark brown	Dark brown
3	pH	3.7 – 4.5	4.0 – 4.3	4.0 – 4.2
4	COD in mg/lit	80,000 – 1,10,000	1,10,000 – 1,30,000	1,40,000 – 1,60,000
5	BOD in mg/lit	45,000 – 50,000	55,000 – 65,000	60,000 – 70,000
6	Total Solids in mg/lit	90,000 – 1,20,000	1,30,000- 1,60,000	1,60,000 – 2,10,000
7	Total Volatile Solids in mg/lit	60,000 – 70,000	60,000 – 75,000	80,000 – 90,000
8	Total Inorganic Dissolves Solids in mg/lit	30,000 – 40,000	35,000 – 45,000	60,000 – 90,000
9	Chlorides (Cl) in mg/lit	5,000 – 6,000	6,000 – 7,500	10,000 – 12,000
10	Sulphates (SO ₄) in mg/lit	4,000 – 8,000	4,500 – 8,500	8,000 – 10,000
11	Total nitrogen (N) in mg/lit	1,000 – 1,200	1,000 – 1,400	2,000 – 2,500
12	Potassium (K₂O) in mg/lit	8,000 – 12,000	10,000 – 14,000	20,000 – 22,000
13	Phosphorus (P₂O₅) in mg/lit	200 – 300	300 – 500	1,600 – 2,000
14	Sodium (Na) in mg/lit	400 – 600	1,400 – 1,500	1,200 – 1,500
15	Calcium (Ca) in mg/lit	2,000 – 3,500	4,500 – 6,000	5,000 – 6,500

Bio-methanation Process Description:

Bio Methanation System is based on the concept of conversion organic matter into biogas. The process of conversion of organic matter into bio gas occurs through a group of bacteria. It has to be carried out anaerobically, since the bacteria which produce methane gas from effluent are strictly anaerobes.

Here the organic matter present in the effluent gets degraded to produce methane gas. Hence here two functions are carried out simultaneously. One is the degradation of organic matter to volatile acids. The second thing is the methane gas is produced from volatile acids.

Process Flow Chart of BioMethanation system for Distillery Raw Spent Wash Treatment

Raw Spent wash:

Receive the spent wash from the distillery. Further cool down of spent wash into around 40 to 45 ⁰C temperature with plate heat exchanger and sludge settled on bottom of buffer tank.

Buffer tank:

The methane formation proceeds between pH 6.0 & 8.5. So the pH in the Buffer tank must be kept above 6.5 and reactors must be operated at a pH of 7.0 to 7.5. Some quantity of treated spent wash is recirculated to maintaining pH in buffer tank. Then spent wash fed to reactor by feed pump.

CSTR Digester:

Spent wash feed is adjusted depending upon the COD load (organic matter) in digester.

Biogas:

Bio gas will be collected at the at top of the reactor and will be stored in a floating type gasholder. Gas holder is fitted with essential safety equipment such as breather valve, flame arrestor etc. Biogas from the biogas holder will be compressed and sent to boiler used as fuel.

Treated Spent wash:

The treated spent wash from the reactor passing through degasser tower to remove gases and then sent to lamella clarifier. The solids are separated from the treated spent wash in Lamella clarifier and returned to the system by recirculation pumps. This recirculation of settled solids helps to maintained adequate population of active bacteria inside reactor. Finally treated spent wash sent to bio composting.