Contributor, The Textile Industry and the Environment, UNEP

22 OVERVIEW Of TEXTILE WET PROCESSING OPERATIONS
• 2.1
WOOL SCOURING
This category of the textile industry includes mills such as wool scouring, top making and general
raw wool cleaning. Raw wool must be cleaned by wet processes before the fibre can be dry processed
to produce fibre, yarn or fabric. Neither cotton nor synthetic fibres require this initial wet cleaning
before processing. Scouring begins with sorting the fleece and feeding il to a hopper. The wool is
then carried through a series of scouring bowls where scour liquor flows counter-current to it. Detergent
is added in the third and fourth bowls to emulsify the grease and oils. The scoured wool is then
dried. In mills where the cleaned wool is converted into wool top, the wool is combed and gilled.
The products are short fibres (used for wool yarn) and long fibres (used for wool top). figure 1
shows the manufacturing processes and sources of emissions arising out of the wool scouring mill.
Since raw sheep wool contains from 25 to 75% suint (which includes water soluble excretions and secretions
of the sheep such as urine, faeces, sweat, blood, dirt, grease, etc.), the production of one kilo
of scoured wool fibre produces one and one half kilos of waste impurities. Because of this, the scouring
process contributes to more than half or even up to two-thirds of pollution load in terms of BOD.
• 2.2
WOOL FINISHING
This category of the textile mill includes woo! finishing along with processes such as carbonising,
fulling, dyeing, bleaching, rinsing, fire proofing, etc. This category is differentiated from other fabric
finishing categories by Ihe wide variety of chemicals used to process wool fabrics. These operations
generate a high effluent load including toxic pollutants such as chromium and phenols. The wool
finishing process and sources of emissions are depicted in Figure 2. The three distinct finishing processes
shown in this diagram are stock, yarn and fabric finishing. Waste generated by the fabric finishing
operation is similar to that generated by all three, therefore only this one process is described bclow.
rr the greige goods are 1000/0 wool, then they are first cleaned to remove vegetable matter by carbanising.
Later, spinning oils and any weaving sizes are removed with the use of a light scour. 100070
woollens are then dimensionally stabilised, principally by felting. Worsted and most wool synthetic
blends are generally not fulled because worsted blends are hard, tightly woven and dimensionally
stable when they arrive at the finishing plant. Woollens are loosely woven, soft and are hence firmed
up by fuJIing.
The fabric is then dyed, in batChes, in vessels called becks, washed and then taken to dry finishing operations.
In this stage, the only dry finishing operation of concern for waste generation ismotb-proofing.
• 2.3
DRY PROCESSING
This category of the textile mill includes yarn manufacturing, yarn texturing, unfinished fabric manufacturing,
fabric coating, fabric laminating, tire cord and fabric dipping, carpet tufting and carpet backing.
The majority of dry processing mills are usually greige mills.
Weaving textile yarns into a fabric requires appljcatioo of size to the warp yarns, to resist the abrasive
effects of the filling yarns as they are positioned by the shuttle action of the loom. Greige mills apply
tbe size and complete the weaving. Many greige mills operate as completely independent facilities. figure
3 shows operations generally performed at this type of greige mill along with sources of emissions.
Mills within the dry processing category lypically carry out dry-type operations, however, some waste
is produced by spillage and vessels or floor cleaning. Some textile greige mills produce a wide variety
of woven goods, each requiring a specially formulated size. In mills of Ihis type, tne size boxes may