Cleaner Production
Until now, the approach
to pollution control has been through either dilution
or treatment. Many developing countries are still at
the dilution or treatment stage. The dilution
approach that involves the discharge of pollutants
directly into the environment mainly relies on the
assimilative capacity of the water, air, and soil to
dilute or neutralise the impacts. Obviously, this
approach can work if the amount of waste is small as
compared to the volume of the receiving environment.
Talking of textiles, in areas where there is a heavy
concentration of dyeing and finishing industry, this
method may not be effective.
Second, the treatment
stage is to collect pollutants at the end of the
process and to separate or neutralise them in various
ways, usually in specially built treatment plants.
Treatment often merely separates the pollutants from
the waste stream, but these still have to be disposed
of somewhere.
Moreover, the costs of
the end-of-pipe treatment approach are one of the
discouraging factors for SSI to invest on this non-productive
process. There is little direct financial return to
the industries, which incurred this expenditure.
Certainly, dilution and treatment, and even recycling,
are not long run solutions. Nevertheless, industries
have to find a solution since the pollution can
impair human health, reducing the productivity of
fisheries and agriculture and damage man-made
materials.
The composition of the
pollution is becoming more complex. Thousands of new
dyes and chemicals are introduced into the market
each year to add to those already there. Moreover,
stringent environmental regulations are putting
pressure on industry to increase its environmental
performance. It is often difficult, however, to
modify existing plants at a reasonable cost.
Cleaner Production, the
preventive way, an evolving concept is considered a
better approach to avoiding and minimising
environmental problems. Increasingly both businesses
and regulators are realising that Pollution
Prevention is a more powerful and economical strategy.
Since processes, those cause pollution also wastes
raw materials. Managers are finding that they can
save money by preventing pollution in the first place,
while increasing efficiency.
Cleaner Production, as
defined by United Nations Environment Programme, UNEP,
is the continuous application of an integrated
preventive environmental strategy to processes and
products to reduce risks to humans and the
environment. Studies reveal that the application of
Cleaner Production concept is good for the
environment because it reduces pollution from
industry. For production processes, the application
includes conserving not only the raw materials but
energy also. Further, it ensures eliminating toxic
processing materials and reducing the quantity and
toxicity of all emissions and wastes before they
leave a production process.
Cleaner Production
requires application of technical expertise,
improving technology, and changing management
attitudes. In nutshell, the implementation of Cleaner
Production technologies involves changes in human
thinking and attitudes about production and the
environment. Experience with Cleaner Production
gained by many countries shows that the companies
could make many improvements in the production
processes at no or very little cost and discharge the
pollutants in a cost-effective way. In India, The
cleaner production methods need more exposure to the
textile industry. Many Cleaner Production techniques
yield substantial savings in production costs.
Alternative
Technologies
According to a UNEP
technical report, it is possible to lower the
pollution problems in a wet processing unit by
reducing the chemical loads, employing Eco-friendly
chemical substitutions, using alternative
technologies, and processing methods. In a study it
was found that very often a large margin of safety is
employed while using the chemicals and many textile
mills use excessive and even unnecessary chemicals.
Often they add chemicals in a dye recipe to
counteract a negative side effect of another
ingredient instead of finding a substitute for the
offending chemical. For example, a company some years
ago would select a certain mineral oil or a paraffin
wax on technical merit alone without any
environmental considerations. It is likely, that now
there is an alternative higher boiling point oil
product available in the market. Further, the
traditional carding oils have 100 per cent BOD values
and may be replaced with non-ionic emulsifiers that
have only 20 per cent BOD.
Now many processors
substitute formic acid for acetic acid in dye baths.
Acetic acid has a five times more BOD as compared
with Formic acid. They also use single-class
dyestuffs like Indigosol, pigments, etc. for dyeing
blended varieties in pale shades in place of two
stages dyeing using two different classes of dyes.
This substitution reduces water and energy
consumption with resultant reduction in wastewater
and air emissions. Experts now recommend use of
reverse dyeing techniques for dyeing blends of
polyester-cotton fabrics. In the reverse dyeing
process, the cotton with reactive is dyed first
followed by dyeing of polyester component with
disperse dyeing. In this way the slightly acidic
disperse dye-bath serves as an after wash for the
fiber reactive. This would conserve both water and
energy. The UNEP report indicate that a new classes
of fibre reactive dyes, e.g. triazine based will
reduce the use of azo dyes and contribute to the
discharge of lower concentrations of dyes during
washing and rinsing.
Excess chemical usage
may also result from the scoop method of chemical
addition rather than precise measurement techniques.
By providing specific instructions and metering
equipment, one can reduce both chemical and water
consumption.
Experts recommend the
reuse of dye-bath wherever possible. The easiest
systems to manage for dye-bath reuse are dye classes
that give high affinity, that is exhaustion, and
which undergo minimum changes during the dyeing
processes. The used dye-bath will usually be hot,
over 60 degree centigrade. Thus starting the next
dyeing at the highest possible temperature saves a
considerable time, fresh water, chemical consumption
and energy.
Experiments have shown
that this methodology can reduce BOD and COD loading
up to 33%. Similarly there may be various other
processes and methods which may result reduction in
water, chemical usage and level of energy consumption.
Thus, a mill should make a careful study of the
various textile processes, with respect to the
minimum requirements of different chemical recipes.
Experts are of the opinion that one can reduce the
amount of process chemicals by 20-50% and the
effluent load in terms of BOD by about 30-50% with
the obvious associated benefit of lower effluent
disposal and operating costs.
