Textile Pollutants
The problem of wastewater from textile industry is
rather complicated, since this industry uses a great
variety of raw materials, intermediate products, and
chemicals. Methods of production also vary widely.
The quantity of wastewater discharged into sewerage
per production unit is roughly 90 to 100 per cent of
total water consumption for the processing.
The qualitative characteristics of wastewater are
variable largely and, even in the same industry
branch, depend on the use of dyestuffs and raw
materials types, liquor to material ratios, and the
type of machines they employ.
The two main sources of pollution in the textile
process are the natural impurities extracted from the
type of fibre under processing along with the
chemicals used. Other factors, which determine
effluent quantity and quality, include the number of
operations used and the degree to which they preserve
water and chemicals in a particular manufacturing
plant.
Wool scouring effluents have high BOD compared to
cotton finishing effluents that contain no grease and
have a relatively low solids content. Synthetic
finishing effluents are generally lower in volume
than those generated in cotton finishing, but may
contain toxic substances, especially from t hose
dyeing streams where chemical dyes with a metallic
ion content are used more widely. Also of particular
concern are some specific compounds that are toxic to
aquatic life.
According to a technical report of UNIDO the
sources of major metal pollutants , i.e., zinc,
copper, chromium, etc. are likely to be the dyes used
in wet processing operations. The causes of air
pollution attributed to textile industry are mainly
from emissions from textile processing, excluding
boiler emissions. Oil mist and organic emissions are
produced when textile materials containing knitting
and lubricating oils, platicisers, and other
materials that can volatilise or be thermally
degraded into volatile substances, are subjected to
heat.
Processes that can be sources of oil mist include
stentering, calendaring, heat setting, drying, and
curing. Carbonisation of wool and some types of spray
dyeing produce acid mist. Solvent processing
operations such as dry cleaning and scouring releases
vapours. The other cause is dust and lin t produced
during the spinning of natural fibres and synthetic
staple as well as by carpet shearing. Add to above be
the releases of excessive nitrogen from the
production and use of nitrogen fertilizers to the
burning of fossil fuels in automobiles, power
generation plants, and industries. This has doubled
the natural annual rate at which fixed nitrogen
enters the land-based nitrogen cycle, and the pace is
likely to accelerate.
