What is a Dye?

A natural or synthetic substance used to add a colour to or change the colour of something. Such substances with considerable coloring capacity are widely employed in the in the production of consumer products, including paints, textile, printing inks, pharmaceutical, food, cosmetics, plastics, photographic and paper industries.

It is estimated that over 10,000 different dyes and pigments are used industrially and over 7 x 105

tons of synthetic dyes are annually produced worldwide.

Types of dyes

1. Natural dyes 2. Synthetic dyes3. Food dyes4. Other dyes like leather, laser and also based on chemical classification

With respect to the number and production volumes, azo dyes are the largest group of colorants, constituting 60-70% of all organic dyes produced in the world. They have a wide range of applications in the textile, pharmaceutical and cosmetic industries, and are also used in food, paper, leather and paints

Market demand for dye and dye intermediates is expected to grow to 1500,000 tons in 2014. The organized sector dominates, with 65% share of the total market, while the unorganized sector controls the remaining 35% of the market. Exports of dyes are also expected to increase by 6.4% due to the shift of production bases from developed countries to India on account of stringent pollution control measures being adopted in those countries. At present, India contributes about 6% of the share in the global market with a CAGR of more than 15% in the last decade.

The dyeing process in various industries has garnered a lot of attention lately because of the emerging concept of sustainability and eco-friendly variants. Due to the toxicity of the dyes and inappropriate discharge of such waste has led to skin diseases and respiratory problems among many factory workers. This has given an impetus to the rising demand for producing textile, paper, cosmetics products through sustainable dyes and processes.

Let us consider its effects in 2 major industries of application :

1.Textile Industry: Till the midst of nineteenth century all the dyes used for textile products were procured naturally, until the invention of mauvine in 1856 by Perkin. Since then there has been no looking back in the production of synthetic dyes because they were affordable, available in a lot of different colors, good color-fastness, and most of all were easy to produce. The textile industry is accountable for using and producing 1.3 million tons of dyes and pigments, most of which are made synthetically.

o The textile industry is one of the largest sectors globally and produces an astonishing 60 billion kilograms of fabric annually, using up to 9 trillion gallons of water.

o 10-25% of textile dyes are lost during the dyeing process, and 2-20% is discharged as aqueous effluents in different environmental components.

In particular, the discharge of dye-containing effluents into the water environment is undesirable because of their color, released directly and breakdown products are toxic, carcinogenic or mutagenic to life forms mainly because of carcinogens such as benzidine, naphthalene and other aromatic compounds

2.Printing Ink: Heavy metals in the colorants used in printing industry have been reduced significantly in the past 20 years, but many are still in use. For example, titanium oxide, chromate, molybdenum, and iron are used as pigments; titanium oxide is used for pearlescent pigments; and aluminum and brass are used in metallic inks. Heavy metals pose unique and serious environmental problems.

One concern is the ability of heavy metals to leech into ground water, which could lead to serious health issues in both humans and wildlife.

A more potent pathway, however, is the inhalation of finely ground metals, such as those created in ink manufacturing.

Environmental impact of DyesAir pollution - Most processes performed in textile mills produce atmospheric emissions. Gaseous emissions have been identified as the second greatest pollution problem (after effluent quality) for the textile industry. Speculation concerning the amounts and types of air pollutants emitted from textile operations has been widespread but, generally, air emission data for textile manufacturing operations are not readily available. Air pollution is the most difficult type of pollution to sample, test, and quantify in an audit.

Water Pollution – The textile industry consumes a substantial amount of water in its manufacturing processes used mainly in the dyeing and finishing operations of the plants. The wastewater from textile plants is classified as the most polluting of all the industrial sectors, considering the volume generated as well as the effluent composition.

In the textile industry, up to 200,000 tons of these dyes are lost to effluents every year during the dyeing and finishing operations, due to the inefficiency of the dyeing process.

In addition, the increased demand for textile products and the proportional increase in their production, and the use of synthetic dyes have together contributed to dye wastewater becoming one of the substantial sources of severe pollution problems in current times.

Unfortunately, most of the dyes escape conventional wastewater treatment processes and persist in the environment as a result of their high stability to light, temperature, water, detergents, chemicals, soap and other parameters such as bleach and perspiration. Dyes can remain in the environment for an extended period of time, because of high thermal and photo stability to resist bio degradation.

Dyes lead to number of environmental & health hazards which are as follows:

1. The greatest environmental concern with dyes is their absorption and reflection of sunlight entering the water. Light absorption diminishes photosynthetic activity of algae and seriously influences the food chain.

2. Many dyes and their breakdown products are carcinogenic, mutagenic and/or toxic to life. Dyes are mostly introduced into the environment through industrial effluents.

3. Triple primary cancers involving kidney, urinary bladder and liver of dye workers have been reported.

4. Textile dyes can cause allergies such as contact dermatitis and respiratory diseases, allergic reaction in eyes, skin irritation, and irritation to mucous membrane and the upper respiratory tract.

5. Reactive dyes form covalent bonds with cellulose, woollen and PA fibres. Certain reactive dyes have caused respiratory sensitisation of workers occupationally exposed to them.

6. The presence of very small amounts of dyes in the water, which are nevertheless highly visible, seriously affects the quality and transparency of water bodies such as lakes, rivers and others, leading to damage to the aquatic environment.

7. The highly toxic and mutagenic dyes decrease light penetration and photosynthetic activity, causing oxygen deficiency and limiting downstream beneficial uses such as recreation, drinking water and irrigation.

8. Azo dyes have toxic effects, especially carcinogenic and mutagenic. They entering the body by ingestion and are metabolized by intestinal microorganisms causing DNA damage.

The parameters of water to be checked for pollution:

o pH o Temperatureo Alkalinity o Dissolved oxygen (DO) o Electrical conductivity

Examples of the effects of environment pollution in India as a result of Dye Industries: In India there are estimated to be about 1,000 small-scale entities and 50 large industrial plants.  While the organized dye industry does dominate the market, there are many unorganized small-scale plants that disproportionately add to the problem of pollution. The top pollutants are chromium, lead and cadmium.

o Total dissolved solids (TDS) o Total suspended solids (TSS)o Total hardness o Chemical oxygen demand (COD)o Total solids (TS)

Maharashtra and Gujarat account for 90% of dyestuff production in India due to the availability of raw materials and dominance of textile industry in these regions.

Jodhpur, India, contains the biggest bloc of textile dyeing and printing industries. About 215 textile industries exist in Jodhpur, with a population of nearly 900,000. 

Pollution Monitoring control program launched for river Kshipra, MP

The results indicate that the effluents affects the water quality which lead to significant environmental and health risk to the rural communities who rely on the receiving water as their source of domestic water purpose without treatment. The study revealed that there was an adverse impact on physicochemical characteristics of the river Kshipra as a result of discharge of untreated effluents of Bhairavgarh Ujjain.

Dyeing Industrial Effluents has adversely impacted the groundwater Quality in Kancheepuram, India

In Tirupur, India, home to scores of factories and workshops where workers dye materials for t-shirts and other garments marketed around the world. Local dye houses have long dumped wastewater into the local river, rendering groundwater undrinkable and local farmland ruined. Despite tougher regulations, a watchful local press, and the closure of companies in non-compliance, water pollution has festered. The city's 350,000 residents, not multinational textile companies, pay the price.

River Bandi affected by textile dyeing and printing effluents, Pali, Western Rajasthan

Legal laws governing dye industry

With respect to the legislation, there is no consensus amongst the different countries concerning effluent discharge, and there is no official document listing the different effluent limit values applied in different countries. Many federal countries, such as the United States of America, Canada and Australia have national environmental legislation, which, as in Europe, establishes the limits that must be complied with. Some countries, such as Thailand, have copied the American system, whereas others, such as Turkey or Morocco, have copied the European model. In some countries, for example India, Pakistan and Malaysia, the emission limits are recommended, but are not mandatory.

With respect to the color, in some countries such as France, Austria and Italy, there are limits for the color of the effluent, but since they use different units, a comparison is impossible.

Listed below are the Acts formed by Central Pollution Control Board.

The Water (Prevention and Control of Pollution) Act, 1974 - To provide for the prevention and control of water pollution and the maintaining or restoring of wholesomeness of water.

The Water (Prevention and Control of Pollution) CESS Act, 1977 - To provide for the levy and collection of cess on water consumed by persons carrying on certain industries.

The Air (Prevention and Control of Pollution) Act, 1981 – To provide for prevention and control of air pollution

The Environment protection Act, 1986 – to provide for protection and improvement of environment

The Public Liability Insurance Act, 1991 – To provide for public liability insurance for the purpose of providing immediate relief to the persons affected by accident occurring while handling any hazardous substance and for matters connected therewith or incidental thereto

The National Environment Tribunal Act, 1995 – To provide for strict liability for damages arising out of any accident occurring while handling any hazardous substance and for the establishment of National Environment Tribunal for effective and expeditious disposal of cases arising from such accident.

In addition to the above the Gujrat pollution Control Board has initiated Plans to create 10,000 skilled personnel with in-depth knowledge of water, air and earth pollution

Suggested measures

The release of improperly treated textile effluents into the environment can become an important source of problems for human and environmental health.

Based on all the problems cited above regarding the discharge of effluents into the environment, it is obvious there is a need to find alternative treatments that are effective in removing dyes from effluents.

Enhance the existing effluent treatment plants through Reverse Osmosis (RO) and the resultant water can be used as fresh water for the region

Industries should switch over to Cleaner Production Technologies (CPT) by using combination of soft flow machines, low salt dyes and membranes filtration. This effectively reduces the water consumption by 50%.

Air Dyeing Technology is a dyeing process that uses air instead of water to dye gar-ments, allowing companies to create garments with vivid designs and colors, without polluting the water and environment.

o It uses 95 percent less water.

o Emits 84 percent less Green House Gases (GHG)

o Requires 87 percent less energy

Ultrasound-assisted textile dyeing: Ultrasound-assisted textile dyeing was first reported by Sokolov and Tumansky in 1941. Due to the revolution in environmental protection, the use of ultrasonic energy as a renewable source of energy in textile dyeing has been increased, due to the variety of advantages associated with it.

Ultrasonic energy can clean or homogenize materials, accelerating both physical and chemical reactions, and these qualities can be used to improve textile processing methods. Environmental concern has been focused on textile processing methods for quite some time, and the use of ultrasonic energy has been widely studied in terms of improving washing fastness. The textile dyeing industry has long been struggling to cope with high energy costs, rapid technological changes and the need for a faster delivery time, and the effective management of ultrasonic energy could reduce energy costs and improve productivity.

Use of activated carbon in the absorption of chemicals in waste from the dye process, which has shown to greatly reduce some of the pollutants in the waste.

Dye fed silk worms' take silk farming to the next level: Researchers have come up with a process wherein by adding a chemical dye to the diet of the silkworms, cocoons are produced in bright; luminous hues. The process is expected to eliminate the requirements of conservative dyeing such as huge volumes of water. It would to result in restricting water and environmental pollution.

The Dyestuffs Manufacturers Association of India, popularly known as DMAI was set up in 1950, to promote and protect trade, commerce & Industries connected with dyestuffs & to encourage friendly feelings & unanimity amongst those engaged in the manufacture of dyestuffs in India. The organization needs to promote environment concerns of this industry and the ways to manage it.

Conclusion

An alternative to minimize the problems related to the treatment of textile effluents would be the development of more effective dye that can be fixed fiber with higher efficiency decreasing losses on tailings waters and reducing the amount of dye required in the dyeing process, reducing certainly improve the cost and quality of the effluent.

The global demand for cheap end products like paints, textiles, printing inks, paper, plastics and food will push dye houses to simply react to local regulations by moving operations to another city. Moral outrage will not convince many leading manufacturers to change their ways; as long as companies do not pay a price for the land and water their suppliers poison, the excessive use and abuse of environmental parameters like air and water to dye products will continue.

http://en.wikipedia.org/wiki/Dye

http://www.cpcb.nic.in/NewItem_19_PollutionControlLaw.pdf

http://textilelearner.blogspot.in/2011/04/problems-of-textile-dyes-in-environment_4787.html

http://nepis.epa.gov/