DISTILLERY
INDUSTRY :
The
main source of pollution from distilleries is the spentwash. Spentwash is a non-toxic,
biodegradable effluent with the following characteristics (Table-3) :
| Table
3: Characterstics of Distileery Effluent |
|
S.No. |
Parameter |
Range* |
| 1. | pH |
4.3-5.3 |
| 2. | Total
Suspended Solids | 12,000-14,000 |
| 3. | Total
Dissolved Solids | 45,000-75,000 |
| 4. | B.O.D.,
20 C, 5 days | 40,000-50,000 |
| 5. | C.O.D. |
80,000-1,00,000 |
* Values are in mg/l except for pH.
Technologies for Treatment
of Spentwash:
During the 80's following technologies were developed
and adopted by distilleries to treat the spentwash:
- Anaerobic
Digestion with bio-gas recovery (Bio- methanation)
- Composting;
and
- Incineration
|
Biomethanation
Biomethanation
is the process involving decomposition of organic matters (and to some extent
inorganic matters) in the absence of molecular oxygen. Bio-conversion of the wastes
results in methane rich gas.
The
advantages of biomethanation in case of spentwash are:
- generation
of bio-gas which can meet more than 60% of the fuel requirements of the distillery
and,
- About
80-90% of BOD is removed from spentwash
|
Over
the years, a number of distilleries in the country have adopted bio-methanation
for treatment of spentwash. The investment made in this system is paid back within
4-5 years. No doubt, the distilleries which adopted bio- methanation are reaping,
the environmental and economic dividend.
| Table
4: Pollution Prevention Pays
(For a 30 kl/day alcohal producing distillery)
|
| Spentwash
generation | :
450 kl |
| Bio-gas
production during bio-methanation | :
25-30 Nm3/kl |
| Average
total biogas production | :12000
Nm3/day |
Based
on the net calorific value,
Therefore, Coal saving |
:12 tonnes/day |
| Saving
@Rs. 2000/tonne of coal | :Rs.
24,000 /day |
| Total
saving through biogas in one year | :
Rs. 72 lakh |
Composting
In this process, the spentwash is mixed with filler materials, such as press mud,
rice husk, wood chips, bagasse pith etc. The mixture . is seeded with cowdung
or specially developed micro-organisms to hasten the process. The process takes
12-14 weeks to be completed and results in black compost, which can be used as
manure.
Incineration
This
process is base on the principal that the spentwash, when concentrate to 60% W/W,
develops sufficient calorific value and can burn by itself without any external
input of energy. This process results in potash rich ash which can be used as
a fertilizer.
More recently the Vasantdada Sugar , Pune, has developed
a process called DIEG (Drying Incineration and Energy Generation) , where coke
like material is obtained and used as fuel in boiler to produce steam and energy.
M/s. Zucker Gassification & Co-generation Ltd., Pune also has developed a process
based on gasification of mixture of spentwash and bagasse to produce gas which
can be used to drive gas turbines to generate power . There is one more process
developed m/s. Consafe Science Ltd., Pune, in which the spentwash is thermally
hydrolysed unde pressure to generate coke which in turn can be used in generation
of steam.
However,
the above processes are yet to .be tried on a wider side.
Efforts
of CPCB in Evolving Standards for Distillery
Recognising
the problem of treating distillery effluent to a level suitable for disposal )
into the river/land, the Central Board constituted an expert group way back in
1980 to evolve Standards (MINAS) developed by the CPCB The MINAS are:
| BOD,(200C,
5 days) | :
30 mg/ I for disposal into inland surface water |
| :100
mg/I for disposal on land for irrigation |
Based on the MINAS
developed by CPCB, Ministry of Environment & Forests, through the EPA Notification,
dated January 8, 1990, specified effluent standards according to the disposal
conditions, i,e, the recipient environment, The BOD (200, C, 5 days) standards
so specified are as follows :
| Disposal
on stream/river | :
30 mg/I |
| Disposal
on land | :100
mg/I |
| Disposal
on land when land is considred as a treatment medium (land treatment) | :
500 mg/I |
| Land
treatment with effective monitoring systems for ground water quality | :
700 mg/I |
The
standards also include stipulations regarding net additional contribution to ground
water quality in terms of BOD not to exceed 3 mg/1 and nitrate not to exceed 10
mg/l,
The method of land treatment, involves designing of the hydraulic
loading, nutrient loading, crop pattern etc" after considering the porosity/permeability
of the soil.
