Denim and Environmental Hazards

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Maeen Md. Khairul Akter

Textile processing is known to be one of the most polluting industrial ssss and a threat to the environment if preventive and mitigation checks are not considered properly. Denim, one of the leading textile product in the fashion world is not different; in fact, the environmental hazards associated with denim processing perhaps is the most dangerous. However, as the demand for denim and jeans are always on the rise among consumers, there is no way but to adopt continuing research, development, and practice of sustainable methods in denim processing so that the environmental impact is at the minimum. For this, we need to have a very clear idea about what are the environmental hazards of denim processing. This article tells you about that.

Water Pollution

Water and dyes are the first issues to look for in denim processing. In this industry, a vast amount of pure water is required and also an equal amount of polluted water is generated. Every year, about 1.1 million tons of synthetic dyes are manufactured according to a recent estimate, and around 17% of synthetic dyes are lost during the process of manufacture and operations. In order to provide pure water to a huge majority of the population throughout the world, mankind faces a major challenge. Due to the insufficient available sources of fresh water and the increase in population and industrialization, it is necessary to reuse wastewater. Industries are forced to accept the responsibility to treat wastewater to minimize pollution due to the increasing legal pressures and restrictions. Material substitution, process modification, inventory control, better management techniques, recovery, recycling and reuse are included in the current commercial textile pollution prevention practices. In order to prevent pollution by source reduction for several types of waste, a relatively comprehensive approach has been developed by the textile industry. In textile dyeing and printing wastewater, much more effort are taken to deal with essential environmental issues such as color residues.

The largest consumers of water and chemicals are denim process houses which are also a producer of wastewater. The natural impurities from the fibres and the chemicals used in the processing of fibres are the sources of pollution. The unit operation of the whole denim process and the extent of in-house conservation measures in practice are the main factors affecting the quality and quantity of the effluents generated. For the colouration of warp sheet in the denim industries, natural indigo and synthetic indigo are consumed. Assuming that a maximum of 90% of dye fed into the fabrics, approximately about 106 kg/year of dyes would be released into the waste streams by the textile industry. Every year approximately 280,000 tons of chemicals are discharged into industrial effluents. Starting from simple organic, and inorganic compounds to various polymers, complex synthesized organic products with this diverse chemical composition are used as the chemical reagents.

Air Pollution

One of the major causes of air pollution is the denim industry. Pollutants released by them into the air are produced by the boilers, power generators, transporting the goods from raw materials to finished jeans etc. It may cause terrible intense health problems to living organisms including human beings due to the emission of toxic gases into the atmosphere. Therefore, denim industry has to reduce the emission of air pollutants necessarily. In denim industry, large amount of Volatile Organic Compound (VOC) is being generated, especially during the dry finishing. The concentration of VOC may vary from 10 mg/m3 of carbon to 350 mg/m3 of carbon. Industries releasing pollutants directly impact the global warming. For the long-term, people who get exposed to the pollutants released have harmful diseases and health problems.

Dyes, Chemicals and Wastewater

The wastewater in large volumes used throughout the process also contains a wide variety of hazardous and toxic chemicals. Colouration is the major source of pollution among the various processes in denim which contains dyes, dyeing additives and other chemicals. Obviously, dyes contain heavy metals which are highly toxic. Various toxic elements such as salts, surfactants, ionic metals and their complexes, formaldehyde, toxic organic chemicals, biocides and toxic anions, detergents, emulsifiers and dispersants are included in the aquatic toxicity.

Hence, the wastewater released is highly polluted and dangerous especially when it gets mixed with other chemicals and disposed of untreated from the textile industry. The characteristics of the wastewater from this industry are high pH, biological oxygen demand (BOD), chemical oxygen demand (COD), high concentrations of total dissolved solids (TDS), suspended solids (SS), chlorides, sulfates and phenols. The majority of these chemicals and dyes are not readily biodegradable, causing severe health and environmental issues. Nevertheless, the biggest source of pollution is the water processed, especially the polluted water which has a large number of contaminants such as dyestuff (indigo/ sulfur and other dyestuffs), solubilizing chemicals, buffer/pH controller, electrolyte, dyeing assistants, sizing ingredients and water, which are generally higher than the permittable limits. Anyhow, the dyes by themselves contain heavy metals and hazardous pollutants. Due to the large market potential of denim, dyeing with natural indigo is not possible because of insufficient production of natural indigo, so the researchers are producing synthetic indigo containing toxic chemicals such as aniline and N-methylaniline residues. Apart from synthetic indigo, denim is often dyed with sulfur, reactive, pigment and direct dyestuffs. Nowadays, heavy metals such as chrome, copper, zinc, etc. are contained in these dyes. These synthetic dyestuffs are non-biodegradable and toxic to living organisms. In general, during the colouration process, the efficiency has never been achieved more than 85%; hence the remaining colours stay behind in the water. Due to the colour of the polluted water, it becomes the biggest threat to biodiversity. During the colouration process, the sizing agents, auxiliary, and chemicals used are not consumed in the respective process. During the rinsing, it could be washed off and will stay in the wastewater and lead to a diverse environmental impact.

Vigorous innovation is going on textile sustainability area especially to tackle the environmental issues caused by chemicals and the use of water. Denim brands are also emphasizing more on sustainable methods of sourcing, manufacturing, and processing so that the consumers can use green and ecofriendly products contributing toward the global climate change mitigation initiatives.

References:

• Environmental hazards of denim processing – I Aravin Prince Periyasamy Faculty of Textile Engineering, Technical University of Liberec, Czech Republic
• Hauser P J, Reducing pollution and energy requirements in cotton dyeing. Text Chem Color Am Dyest Report 32:44- 48 (2000)

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