Basics of pollution & pollutants, source of pollutants & Chemical Hazards.
- What is Pollution :-
The contamination of soil, water, or the atmosphere by the discharge of harmful substances is known as the act or process of polluting or the state of being polluted,
Generally pollution is an outcome of human activity & impact of other living animals on natural atmosphere.
The textile industry is one of the most pollutants releasing industries of the world. … Besides, 20 percent of all fresh water pollution is made by textile treatment and dyeing. Pollutants released by the global textile industry are continuously doing unimaginable harm to the environment. It is essential to have sharp focus on pollution & pollutants created by Textile industry.
Impact of pollution is observed on Air, Water & Soil.
- It Disturbs the Natural cycles (seasonal changes) in atmosphere.
- Global warming
- Ozone layer depletion
There are three basic needs that a man possesses food, clothing, and shelter. When we think of pollution, we envision coal power plants, strip-mined mountaintops and raw sewage piped into our waterways. We don’t often think of the cloths on our bodies. The global textile and clothing industry is bound to be huge, as it fulfils the second basic requirement of man. The consumption of textile products is very huge & is increasing day by day due to increase of population & also increase in sq. meter consumption per person. Ultimately the overall impact the apparel industry has on our planet is quite large. Fashion is a complicated business involving long and varied supply chains of production, raw material, textile manufacture, clothing construction, shipping, retail, use and ultimately disposal of the garment. It is said that textile is the second largest polluter (after paper industry) in the world. A general assessment says that, right from the pesticides used in cotton farming, the size used in fabric manufacturing, the toxic dyes used in manufacturing and the great amount of waste generated during disposal of garments. Other supporting systems also generate lots of pollution load which includes coal for steam generation, transportation & packing material. Pollutants released by the global textile industry are continuously doing unimaginable harm to the environment. It pollutes land and makes them useless and barren in the long run. Surveys show that cotton consumes the highest amount of harmful pesticides and fertilizers. Majority of them fall on land while they are sprinkled on the crop. Similarly, textile manufacturing units release hazardous waste into the nearby land.
B. What are Pollutants :-
Here we link this word with chemical pollutants. The substance that pollutes something, especially water or the atmosphere are known as chemical pollutants.
Pollutants are bifurcated by various methods we will see each one in different tables.
Pollutants’ generated during various processes during Textile processing
The textile industry is water intensive and produces pollutants of different forms. The manufacturing operation also generates vapors’ during dyeing, printing and curing of dye or colour pigments. Dust emission is associated with Fibre processing / boiler operation. Other than these process operations, textile mills have wood, coal or oil fired boilers and thermic fluid heaters which are point emission sources. Major environmental issues in textile industry result from wet processing. Wet processes may be carried out on yarn or fabric. The transformation of raw cotton to final usable form involves different stages. The various important wet processes involved in the textile industry are as follows:
Sizing / Slashing: This process involves sizing of yarn with starch or polyvinyl alcohol (PVA) or carboxyl methyl cellulose (CMC) to give necessary tensile strength and smoothness required for weaving.
Desizing: The sizing components which are rendered water soluble during sizing are removed from the cloth to make it suitable for dyeing and further processing. This can be done either through conventional process of acid steeping or through enzymes.
Scouring / Bleaching: This process involves removal of natural impurities such as greases, waxes, fats and other impurities. The desize cloth is taken for scouring. This can be done either through conventional method (kier boiling) or through modern techniques (continuous scour). Kiering liquor is an alkaline solution containing caustic soda, soda ash, Hydrogen peroxide, Peroxide stabilizer, with small amount of detergent. This process removes the natural coloring materials and renders the cloths white.
Mercerizing: The process of Mercerization provides luster, strength, increases dye affinity and abrasion resistance to fabrics. It is generally carried out for cotton fabrics only for easy dyeing. Mercerization can be carried out with the help of highly concentrated caustic soda (250 to 300 GPL) with alkaline stable wetting agent.
Dyeing & Printing: This is the most complex step in wet processing which provides attractive color on the product. Dyeing is carried out either at the fibre stage, yarn stage, or at fabric stage. For dyeing process, hundreds of dyes and auxiliaries are used. In textile industry, various types of fibres are used which leads to different process & various Dyes & chemicals printing paste add to the load of pollution drastically.
Finishing: Finishing process is a specialize process which leads to use of various specialized chemicals & ultimate pollution load is increased. The finishing chemicals are more harmful to human health & also are environmental hazards.
The combination of all above processes used in textile manufacturing, large volume of water with various pollutants is generated & it need to be treated in Effluent treatment plant. There are two wars to reduce pollution load 1) By treating effluent in correct manner with correct discharge norms. 2) By avoiding / reducing use of chemical hazards in process. It is fact that, textile industry is highly water consuming industry. In addition to this, the effluent characteristic and effluent quantity vary according to the processes involved, chemicals used and the scale of operation. Therefore, quality of effluent from one industry varies from the industry. As the textile manufacturing units use different type of raw materials, chemicals and processes. As per market demand, textile units change their product mix & lead to variation in effluent characteristics which leads difficulties in treatment at ETP. To avoid use of hazardous chemicals is the only solution for pollution prevention.
There are three types of Chemical hazards
Chemical hazards are further categorized by its chemical nature into 11 priority groups as under;
- Azo Dyes
- Brominated & Chlorinated Flame retardants
- Chlorinated aromatics
- Chlorinated solvents
- Organotin Compounds
- Short Chain Chlorinated Paraffin’s (SCCPs)
- Heavy metals
- Per-fluorinated Chemicals (PFCs).
The restrictions on these chemical groups were imposed as & when its severity was identified. Above pic shows the year when particular hazard was banned (Pic is from IKEA brand)
In order to reduce the use and impact of harmful substances in the industry, it is essential to focus on entire supply chain starting from fibre generation to end consumer. This includes suppliers of raw material & chemicals, production houses, accessories manufacturers, packaging material suppliers, screen-printers, laundries etc…
RSL & MRSL:-
Restricted Substances are chemicals whose use or presence is banned in a particular end-product such as finished article or garment. Restricted Substances List or RSL is a comprehensive list of all chemicals that are restricted of banned from use on products. RSLs are developed by individually by Brands, Eco-labels or legislations and are continuously updated based on international, federal and local governing bodies. MRSL is a next step to control the use of restricted substances right from manufacturing stage. The MRSL differs from a RSL because it restricts hazardous substances potentially used and discharged into the environment during manufacturing, not just those substances that could be present in finished products. The MRSL takes into consideration both process and functional chemicals used to make products, as well as chemicals used to clean equipment and facilities. It addresses ANY chemical used within the four walls of a manufacturing facility. Thus MRSL has broaden the area of RSL.
A typical RSL manual contains the following:
- Substance name
- CAS Number
- Limit Values of each restricted group
- Terms such as Not Detected and Detection Limit
- Test Method
- Regulations under which the chemical group is restricted.
RSLs Focus on End-Product: Certain chemicals used at different stages of production are released in the environment through waste water, air or sludge. RSLs are focused only on restricted substances in the end product and do not monitor the presence of these chemicals in waste water or sludge. RSL compliance is monitored only through random testing on the samples of finished product. But, this is like solving the problem after the damage has been done! Due to these limitations, Brands have shifted focus from RSLs to Manufacturing RSLs or MRSLs. One need to understand the difference between RSL & MRSL.
An important point to consider is that if hazardous chemicals are restricted at the factory gate before they even enter the manufacturing facility, theoretically they will not be present on the finished product. This means
- The amount of product testing can be reduced significantly.
- Fewer products to test, and less transportation to testing labs saves money.
- Fewer garments need to be destroyed which is a requirement for testing.
Source of pollutants
Above list is a guidance for possible presence of restricted substances. One can study MSDS & TDS for correct selection of chemicals & dyes in process. Even chemical manufacturer can guide for selection of Dyes& chemicals for restricted substances.
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