Of all dyes produced across the world, 11 per cent goes out as effluents. 2 per cent from manufacturing and as much as 9 per cent from colouring. Each year, India produces 64,000 tonnes of dyes, 7,040 tonnes of which are directly discharged into the environment. Enough to dye the river Sabarmati!
While colours brighten our world, they are also ubiquitous and pervasive. We're not talking nature here, but products that are created by industry. Like food colours, textile dyes, printing inks, pigments, acids, paints, even colours used in plastic. What goes into them? How are they manufactured? What is the monitoring mechanism? What are the procedures governing effluents? Can using them affect our health? What about the other end of the spectrum? What is the footprint we leave by using so many coloured products? Does industrial discharge affect the drinking water sources of villages and towns far away? What are the regulations and how can they be enforced?
Issues like this also need to be addressed, says kushal pal singh yadav
United Colours of Industry
Colours are inescapably embedded in everyday life. So it's critical to know, and to regulate, the way they operate. Having said that, it's not easy to recognise the problems associated with their use. Adulteration in food colours, or allergic reactions to elements in fabric apart, consumers are unaware of problems caused by agents and vehicles of colour.
But a look at the tailpipe in any industrial zone can cure that.Colour problem comes from two types of industries:
• Makers or users of colouring matter: dyestuffs, pigments, textiles, dyeing and tanneries are the principal ones
• Users of raw materials with colour as by-product: pulp and paper sector (where lignin imparts colour to effluents) and distilleries (where spent water is highly coloured)
The Central Pollution Control Board (cpcb) has listed the dyes and dye intermediates, pulp and paper and tanneries as heavily polluting industries. Untreated (and sometimes even treated) effluents from these industries, released into rivers, lakes or through the drainage systems, seep into the groundwater and adjoining water bodies.
Colours that last: dyes & dye intermediates The huge growth, by over 50 per cent of the Indian dyestuff industry during the last decade, makes it the second largest producer of dyes and intermediates in Asia. The cpcb puts their number at 900 units. Only a third of these are in the organised sector, while the remaining come from the unregulated small-scale sector, which produces more than half of India's aggregate volumes. Most of these units are located in Gujarat (more than 60 per cent of the total production) and Maharashtra. In India, dyestuffs are consumed mainly by textile, paint and printing ink industries. The textile industry consumes up to 80 per cent.
Budget over quality
The domestic textile industry looks for manageable costs rather than consistent quality. So the bulk of its demand for dyes is met by the small-scale sector, while the organised sector looks to exports or high-end producers. The small-scale sector's substantially lower investment in pollution control measures also makes it more economical.
We dye, they just buy
Dye production in India is estimated to be around 60,000 tonnes, or about 6.6 per cent of world production. There are around 700 varieties of dyes and dye intermediates produced in India, mainly direct dyes, acid dyes, reactive dyes and pigments. Most of these dyes have not been evaluated for their impact on health and the environment. Yet, they are widely used by textiles, leather, paper, paints, plastics, printing and even in the food industry.
The largest producer of dyes in the world is Germany at 22 per cent, followed by the us at 18 per cent. Till recently, big global players (American Colour, Atlantis Chemicals, Bayer AG and Hoechst AG) controlled 60 per cent of the global dyes output. However, a gradual shift is discernible in global dye production. The number of large-scale dyestuff manufacturers in the us has reduced drastically (from 21 in 1976 to a mere ten in 2001) and the overall share of developed nations has also dropped from 65 per cent to 50 per cent. Faced with spiralling labour and environment costs, developed countries are slowly disengaging themselves from the manufacture of dyestuffs (setting up a dyeing plant in India, for instance, costs just a quarter of what it would to start up a similar plant in the West). Lack of enforcement and monitoring of regulations related to environment also make the industrialising countries in Asia a lucrative place to set up polluting industries. As China, South Korea, Taiwan and India become the new large producers, the extent of environmental and health problems are likely to shoot. Thus, the South ends up paying the real ecological costs to produce dyes for the North.
Indian dyestuffs are exported to the European Union, the us, Indonesia, Hong Kong, South Korea and Egypt, of which the us alone accounts for almost 20 per cent. World demand for dyes and organic pigments, forecast to increase over 5.2 per cent per year, reached us $14.2 billion in 2004, with volume demand reaching 1.5 million tonnes over the same period. In terms of usage patterns, China, India, South Korea and Taiwan demand dyes, while North America, Western Europe and Japan prefer to use organic pigments.
Paints are big business
The predominant use of paints is by industry (automotive paint, high performance coating, powder coating and marine paint) and architecture (enamel, distemper, emulsion, exteriors and wood finishes). Paints have market volumes of up to 600,000 tonnes, adding up to almost Rs 6,200 crore. The unorganised sector accounts for 45 per cent of this and comprises about 2,500 units that manufacture low technology paints for local use. (see pie charts: Paint makers and Where it's going)
Unlike textiles, the bigger share (55 per cent) here belongs to the organised sector, which is dominated by a few large players. With an annual growth of 10 to 12 per cent, domestic paint use in industry is growing at 15 per cent or Rs 1,000 crore per year and paint use in architecture/building at eight per cent or about Rs 2,200 crore.
Textiles: Good, Bad, Ugly
The textile industry occupies a vital place in the Indian economy. Indian textile exports have risen from Rs 100 crore in 1967-68 to Rs 34,800 crore in 1997-98. Of this, readymade garments constitute nearly 50 per cent of India's total textile exports and employ an estimated 35 million people directly.
Wet processing, dyeing and printing of textiles in India is mostly done in the decentralised sector. Most of these units buy their inputs from local markets and therefore lack detailed information about eco-standards and possible substitutes, technical know-how and financial resources to invest in pollution control measures.
About 80 per cent (more than 51,000 tonnes) of all dyestuff produced in India is used by textiles alone. With its needs for dyeing and printing, the textile sector is probably the worst offender when it comes to releasing coloured effluent discharge and Ludhiana, Panipat, Pali, Bichchri, Patancheru, Jetpur, Ahmedabad, Surat and Tirupur are some of the country's most polluted zones.
As a result, textile manufacturers have faced the most protests from local people who they affect and a fair amount of litigation as well. Though in the last decade, some change has been forced, mainly under pressure from court rulings and local people's movements, several problems still plague this sector.
Leather that weathers
India has about 3,000 tanneries with a total processing capacity of 700,000 tonnes of hides and skins per year. About 35 large firms are reported to account for 60 per cent of India's leather exports. More than 90 per cent of the tanneries are small or medium-sized, with processing capacities of less than two to three tonnes of hides/skins per day. In India, tanneries process sheep, goatskin, cow and buffalo hides, using both vegetable and chrome tanning. The highest concentration of tanneries in India is along the banks of the Ganga river in North India and around the Palar river system in Tamil Nadu.
Most tanneries in India use old technologies and production methods. Even in large tanneries, the technology used is inefficient. This is largely responsible for the wasteful use of water and chemicals, high load of effluent pollutants and low productivity.
A study of India's tanning industry, carried out on behalf of the Union ministry of science and technology, found that the chemical consumption in Indian tanneries is about 25 to 30 per cent higher than international norms. So a tannery that needs only 100 tonnes of colour ends up using 130 tonnes. The extra 30 tonnes goes out as waste and contaminates the soil and the water around the tannery.
However, export demands for higher standards may fuel some changes in environmental standards. For instance, Germany, a major importer of leather and leather goods from India, banned the import of leather products containing more than 5 milligramme/kilogramme (mg/kg) of pentachlophenol (pcp) in 1990.
This was followed by a German ban on the import of leather and textiles treated with a number of azo dyes in 1994. The use of benzidene and arylamines in dye formulations has also been banned in Germany since 1995.
Pulp & paper
In the large-scale domestic pulp sector, 16 mills manufacture several different kinds of coloured products; on an average, each of these account for 4.12 per cent of total volumes of pulp and paper.
Colouring matter in wastewater from pulp/paper mills is organic in nature and includes wood extractives, tannins, resins, synthetic dyes and lignin. The specific dye consumption for the large-scale pulp and paper sector is 4 kg/bone dry tonnes of coloured product. Coloured paper is obtained by dyeing the paper stock or the paper surface (size press, paper coating). Additionally, fixing agents and other additives are used to improve dye fixation and to obtain better dyeing results. Both inorganic and organic pigments (for instance, azo and phthalocyanine types) and carbon black are used for paper dyeing.
Colour impacts the environment when it is released into water. Paper mills, which experience several changes of tints or shades each day, have to get their water circuits cleaned every now and then. Discharge of coloured pulping effluents in water inhibits photosynthetic activity of aquatic biota by reducing the penetration of sunlight, besides direct toxic effects on biota. The colour compounds also collect metal ions and may import contamination by heavy metals.
India's large-scale pulp and paper sector discharged more than 100 tonnes of dyes as unused dyes each year between 1998 and 2001.
|Block the print
Pollutants associated with textile
||Discarded print paste and clear (pigment printing)
||Print paste (wet printing)
||Drying/curing oven emissions (solvents, acetic acid)
||Nonaqueous oil/water thickeners, machine cleaning, screen cleaning
||Discarded print paste, colour kitchen operations, implement cleaning
||Discarded print paste, photo operations, reducing agents in discharge printing, screen making, engraving operations
|Water (and heat)
||Washing of printed cloth, desizing operation
Back-coating operations, carpet printing
Sanganer, a small industrial town near Jaipur, is famous for hand block printed fabrics. But for its residents, dyeing units are a serious problem. Says Purshottam Singh: "Sometimes the supplied water is red and at other times bluish. How can we drink this?".
Sanganer's problem is typical of areas where industrial units operate freely. Colour in water is a pointer to contaminants ranging from dissolved organic material, high levels of disinfectants and excess of its by-products and inorganic contaminants like metals. The average hazard limit varies from five to 30 colour units, but colour can be objectionable even at 15 units.
What you see, what you get?
The limits for colour in potable water are based on visual or "aesthetic" parameters. Given a choice between visibly coloured water and a colourless source that may be more unsafe, people tend to opt for the latter. Colour is also determined by a visual comparison with a standard solution (see box: Gauging colour in water).
New drinking water standards prescribed by the Bureau of Indian Standards (is 10500) set colour standards at five colour units as the desirable limit and 25 colour units as permissible limit in the absence of alternate source.
The us Environmental Protection Agency (usepa) lays down 15 colour units as the secondary standard for drinking water in the us . These standards are non-enforceable guidelines regulating contaminants that may cause skin or tooth discoloration or aesthetic effects such as taste, odour, or colour in drinking water.
usepa also recommends secondary standards for water systems but does not require compliance. States, however, may adopt them as enforceable. On the other hand, the Drinking Water Inspectorate of England and Wales has prescribed the colour standard for water supply at 20 colour units. Unlike India and the us, these standards are not only prescribed but are enforceable in the uk .
No fix on industrial discharge
Colour standards for industrial discharge vary. Countries like Mauritius have set up standards for colour discharged from dye manufacturing, textile dyeing and paint units.
In India, however, the Central Pollution Control Board (cpcb) does not stipulate any standard for colour in the wastewater discharged from industries, except relating to dyes and dye intermediates. It just recommends that, "All efforts should be made to remove colour and unpleasant odour as far as practicable." For dyes and dye intermediates, the standard for colour in the effluent that's discharged has been set at 400 Hazen units.
But colour standards are not completely indicative of the pollution in water and effluents that can be caused due to colour. Total suspended solids, total dissolved solids, foaming agents and metals like aluminium, copper, iron and manganese are indicative of colour in water and should also be considered when tracing pollution caused by colour in water bodies.
Similarly, certain dyes in wastewater include toxic metals. The presence of metals in dyes can be caused by the use of mercury or other metals as catalysts during dye making. Mercury, besides being hazardous to health, is a metal that can also cause pollution problems during the manufacturing process. Some dyes also include metals as an integral part of the dye molecule.
metals in structure
What do industry and consumers look for in a dye? Permanence: the colour is unaffected when exposed to light, washing, chlorine or ozone. This is why dye chemistry produces dyes that last forever. The result of their success: outstanding permanence, but resistance to treatment or removal in wastewater treatment systems.
Most experts agree it is extremely difficult to remove colour from wastewater. There is no universally applicable technique for all conditions. Research and development, therefore, focuses on sector-specific methods and technologies to remove colour and similar contaminants from different kinds of waste streams. Such technologies use three kinds of processes:
adsorption: Adsorption, the attachment of the molecules of a liquid or gaseous substance to the surface of a solid, is commonly used to remove colour. Most wastewater treatment systems use activated carbon, a crude form of graphite commonly made from wood, coal, lignite and coconut shell, as an adsorbent. Activated carbon is highly porous; this imperfection differentiates it from tight graphite, but also provides it a very large surface area: 5 grammes of activated carbon is equivalent to the surface area of a football field. So, it can adsorb a wide range of components. Its physical adsorption forces are the strongest. Its adsorbing porosity is the best known to humankind.
filtration: In simple terms, a crossflow filtration system separates an influent stream into two effluent streams: the permeate and the concentrate. The former is what has passed through the semi-permeable membrane. The concentrate stream contains constituents the membrane rejects.
Nanofiltration is a proven method for colour removal because it can operate at much lower pressures.
electrolytic treatment: Research shows this can remove colour from wastewater, achieved by passing polluted water between two or more electrodes; colour-imparting material is absorbed, producing decolorisation.
ozonation: Due to its strong oxidative nature, ozone (combined with other physical, chemical or biological processes) can treat complex industrial wastes: colour molecules break down quickly. Industry and municipal bodies use this process extensively to remove colour from wastewater.
coagulation and flocculation: Both are crucial to water and wastewater treatment, and are commonly used to remove suspended matter or colour. The commonly used coagulants are ferric chloride, ferric sulphate and alum.
Typical processes include biologically activated sludge oxidation and post coagulation, followed by chemical oxidation of the final effluent by sodium hypochlorite (naocl).
But the most important strategy is to minimise pollution. Simple steps exist: maximising dye use in the dyebath (thereby reducing what goes out as effluent); maximising dye fixation (reducing usage of dyes) and minimising washoff. These reduce dye consumption by as much as 10 to 20 per cent.
Dyes without metals should be used wherever possible. If a shade cannot be matched with a metal-free colour (say, with bright green, royal blue direct and fibre-reactive colours), reducing metal-bearing dye content is often possible by substituting part of the dye.
In sum, a question remains: how many factories actually use them? More than 70 per cent of dye manufacturing units are in the small-scale industries (ssi) sector, producing more than half of the total dye and dyestuff in the country. The ssi sector pays no heed to environmental regulations: effluents are discharged sans treatment. The same occurs in the unregulated textile dyeing sector. Pollution problems in towns like Panipat, Pali, Bichchri, Jetpur, Tirupur and Ludhiana testify to this fact.
The colour problem will only increase in future. Polluting industries in the West, facing stiffer environmental regulations, continue to shut shop and shift to countries like India, helped by weak enforcement and monitoring. Competition from countries like China will drive manufacturers to look for cheaper options. In this, the casualties will be health and the environment: sub-standard and cheaper inputs mean highly polluting, conventional materials and technologies will remain in use with no incentives for switching to better, less polluting technologies.
Regulatory authorities will have to look for novel solutions. The situation is unique; the solution, too, must be so. To start with, a major improvement in enforcement and monitoring is the need of the day. Authorities will have to encourage research and development to look for solutions that work in our conditions. Consumers will have to be better informed about the dangers the products they use, can cause. As it has been in the past, a demand for change--and from the consumers--is a much better trigger to improve things than any threats from the government.
Colours will continue to be an integral part of our lives. But so will be the problems associated with them. Colours cannot, and should not, be wished away. But dealing with the problems they pose is also not easy. So the next time you see that colourful fabric or notice that beautiful paint on the wall, just remember what went behind colouring it.
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