Contributor, The Textile Industry and the Environment, UNEP

48 CLEANER PRODUCTION TECHNIQUES AND PROCESSES
.4.2 OPTIMISATION OF CHEMICAL USAGE
The choice of process chemicals used is a key decision for reducing impacts. Processing chemicals
have a range of potentially hazardous properties. The wide choice of substances now available on
the market means that often it is possible to substitute safer chemicals for thost": used traditionally.
This is particularly true for some of (he toxic dyestuffs, but opportunities aJso exist in other areas.
The higher cost ofsome safer substances can usually be justified through benefits such as lower worker
illness and savings from the reduced cost of required safety measures.
Some toxic chemicals are now banned or severely restricted in certain countries in order to encourage
the use of safer substitutes. The International Register of Potentially Toxic Chemicals (JRPTC) in
Geneva, provides an up-lO-date list (for IRPTC's address see Annex D). Table 16 in Chapter 6 shows
an extract from the 4th edition of this list.
In addition to acute toxicity, the possibility of long-term exposure effects such as carcinogenicity should
also be kept in mind. This can be a concern for chemicals which have been inadequately tested and
where the low acute toxicity may give managers a false sense of security. The International Agency
for Research in Cancer (lARC) has classified over 700 chemicals for carcinogenic risk to humans.
No dye has yet been included in Group I (carcinogenic to humans) but Annex D includes a list of
dyes classified in Group 2A (probably carcinogenic to humans) and Group 2B (possibly carginogenic
to humans). Some national and regional organizations may also keep lists of chemicals subject to
local restrictions.
In all cases process chemicals must be carefuJly handled in accordance with the safety advice of the
manufacturer or any other authoritative source. Safety advice can be found in the Materials Safety
Data Sheet (MSDS) which is available from manufacturers, or in health and safety guidance relating
to specific chemicals where it is published by other institutes. A sample MSDS is shown in Annex D
along with international sources of information on toxic chemicals.
In addition to problems of possible toxicity, textile processing uses a variety of chemicals with considerable
BOD and COD. It is possible to lower these pollution problems by reducing the chemical
loads, since very often a large margin of safety is employed. In many cases, knowingly or unknowing­
Iy, these safety margins may be applied more tightly at a textile mill to eliminate the need for
reprocessing.
For this reason a careful study of the various textile processes, with respect to the minimum requirement
of different chemical recipes, can be particularly important. It is possible to reduce the amount
of process chemical by 20-50070 by adopting such measures which will in turn reduce the effluent load
in terms of BOD by about 30-50010. Another obvious benefit is lower operating costs.
One strategy to achieve chemicals and effluent reduction, especially in the context of large textile
processing mills, is to use automated chemical dispensing. Many large and modern mills have
implemented automated chemical and dye dispensing systems. Such systems will form one of the
textile dyeing industry's major innovations over the next few years.
An automated chemical dosing system offers some important advantages over the manual method.
Flexibility is gained by running smaller lots. Automation also offers faster delivery times, better
laboratory-LO-dye house correlation, a wider variety of styles and higher quality. Handling of some
chemicals is hazardous so an automated system also minimises the chances of worker injury.
The effluent load can also be reduced by effective recovery practices and the re-use of process chemicals
to the maximum possible extent. Preparation chemicals (including optical brighteners and tints)
must however be selected in such a way that their re-use does not create quality problems such as
spotting.