TEXTILE INDUSTRIES

INTRODUCTIONTextile wastewater includes a large variety of dyes and

chemical additions that make the environmental challenge for textile industry not only as liquid waste but also in its chemical composition.

Main pollution in textile wastewater come from dyeing and finishing processes.

These processes require the input of a wide range of chemicals and dyestuffs, which generally are organic compounds of complex structure.

Because all of them are not contained in the final product, became waste and caused disposal problems.

Water is used as the principal medium to apply dyes and various chemicals for finishes.

Major pollutants in textile wastewaters are high suspended solids, chemical oxygen demand, heat, colour, acidity, and other soluble substances.

Substances which need to be removed from textile wastewater are mainly COD, BOD, nitrogen, heavy metals and dyestuffs.

COTTON TEXTILE WASTES An integrated cotton textile mill produces its own yarn from the

raw cotton.

This process includes opening & cleaning,picking,carding,drawing,spinning,winding,and warping.

All these are Dry operation and as such as do not contribute to the liquid waste from the mill.

Different type of waste generated are Appearance,Ph,Color,Heavy Metal, Suspended Solid, Total Dissolved Solid, Chemical Oxygen Demand (COD),Bio Chemical Oxygen Demand (BOD),Oil & Grease, Surfactant.

The entire liquid waste from the textile mills comes from the following operation of

i. Sizing(caboxymethyl cellulose (CMC), polyvinyl alcohol (PVA))

ii. Desizing(mineral acid)iii. Scouring(Caustic soda, soda ash, detergent )iv. Bleaching(sodium hypochlorite (NaOCl) or hydrogen

peroxide (H202))v. Mercerizing (caustic soda solution) vi. Dyeing (vat dyes, developing dyes,naphthol dyes, sulfur

dyes, basic dye, direct dyes etc.)vii. Finishing (starches,dextrines,natural and synthetic waxes,

synthetic resins)

NATURE OF WASTE GENERATED AT EACH PROCESS

WOOLLEN MILL WASTES• Woolen fibre, unlike cotton is a fibre of animal origin. Wool

contains considerable quantities of dirt, grass , etc.

• Contain 30% fibre and 70% foreign matter.

• In extreme cases, raw wool may contain as little as 30% fiber, 70% foreign matter, of which 45% is grease.

• Wooling waste originated from scouring, carbonizing, bleaching, dyeing,oiling,fulling and finishing operations.

• Scouring: Wool grease and foreign matters are removed by Scouring with wool in hot alkali, soap and soda ash.

• Carbonization: It is a process in which hot concentrated Sulphuric acid is used to convert the vegetable matter in the wool into loose, charred particles, followed by mechanical dusting of the same.

• Dyeing: Hot dye solutions are circulated through the wool packed in a metal container. Waste water generated by dyeing is highly colored and contains many toxic substances.

•Oiling: Usually olive oil or barg-oil-mineral-oil mixture is mixed with water and sprayed on the wool to increases cohesion of the fibers and aids in spinning operation.

•Fulling: The loosely woven wool from the loom is shrunk into tight, closely woven cloth. To aid this process, chemicals like soda ash, soap etc are uesd.Excess fulling chemicals, all of the oil etc are washed out of the fabric in a finishing process.

•Finishing: Waste from a dyeing and finishing process are contributed by the spent liquors and by subsequent washing of wool after bleaching, dyeing, and finishing.

EFFECTS OF MILL WASTES The crude waste if discharged into streams causes rapid

depletion of the dissolved oxygen of the streams.

The alkalinity and the toxic substance like sulphides and chromium affect the aquatic life and also interfere with the biological treatments.

The colour often renders the water unfit for use for some industrial purposes.

The presence of sulphides makes the waste corrosive particularly to concrete structures.

WASTE WATER TREATMENTS

Preliminary

PRIMARY

SECONDARY

TERTIARY

PRELIMINARY TREATMENT: It involves removal of large solids such as rags, sticks, grit and grease that may result in damage to equipment or operational problems (Physical treatment).PRIMARY TREATMENT: It involves removal of floating and settable materials, i.e. suspended solids and organic matter (Physical and Chemical).SECONDARY TREATMENT: It involves removal of biodegradable organic matter and suspended solids (Biological and Chemically).TERTIARY TREATMENT: It involves removal of residual suspended solids / dissolved solids (Physical, Chemical and Biological).

CONCLUSION•It has become utterly necessary to reduce the pollutants emitted by the textile industry.

•Contamination of the air, water, and land by textile industries and its raw material manufacturing units has become a serious threat to the environment.

•It has endangered the life of human beings and various other species on Earth. Global warming is a direct result of the pollutants released by such industries.

•It also causes harmful diseases and health issues in people getting exposed to the pollutants in the long run.

•The use of organic raw material can help in fighting the emission of pollutants by the textile units.

•Organic cotton is especially beneficial as the production of cotton asks for the maximum amount of pesticides and fertilizers.

•Besides, the waste generated from textile manufacturing plants should be processed in a manner that it is free from toxic chemicals before it is disposed.

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