This document discusses the impact of the textile industry on water pollution and proposes measures for more sustainable development. It notes that textile production heavily pollutes water sources through discharge of toxic chemicals from dyeing and other wet processes. It then outlines specific chemicals like NPEs that are hazardous and alternatives like natural dyes and bio-processing that can reduce pollution. The document concludes by emphasizing the need for all stakeholders to adopt cleaner production techniques to protect the environment and ensure long term economic viability of the textile industry.
2. SUSTAINABLE DEVELOPMENT OF TEXTILE INDUSTRY
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1. INTRODUCTION
The textile industry has been a major contributor of water pollution globally. Wet processing of
textiles leads to the discharge of large quantities of effluent containing toxic chemicals due to
processes such as dyeing, washing, sizing and finishing. China is the worst water polluting country
in the world, with 70% of its lakes, rivers and water reservoirs affected. About 20% of the non-
biodegradable organic pollutants in China’s waterways are from discharges from the textile
industry [1]. Unquestionably, the current approach of control over water pollution; which relies on
wastewater treatment plants limiting certain pollutants, have been unable to prevent industrial
water pollution of hazardous and persistent chemicals. Essentially, water treatment plants are
unable to remove all of the carcinogenic toxic pollutants; they either pass through the treatment
process untreated, are converted into other polluting substances, or accumulate in residues, in the
form of waste sludge.
2. EFFECT OF TEXTILE INDUSTRY ON WATER POLLUTION
Textile products such as clothing and fabric based shoes sold by international clothing brands are
manufactured using nonyl-phenol ethoxylates also called NPEs. NPEs are used as surfactants in
textile production which subsequently break down to form biologically persistent, toxic and
hormone disrupting nonylphenol (NP). When released in the water stream, NPEs break down in
rivers to form the NP [2]. Even in suppliers where adequate treatment facilities are available, they
are incapable of fully eliminating NPEs, and can only partially degrade them – often catalyzing its
conversion into toxic form. It has been found that NPEs accumulate in the tissues of aquatic
organisms such as fish, and to increase in concentration through the food chain, traces of which
are have been found in humans as well. Washing of these clothing items can release residual NPEs
contained within the product into sewage systems. Even though the level of NPEs in one washing
cycle is small, collectively the total volume of clothing washed means that the amount of NPEs
released into the streams may be substantially high.
3. MEASURES TO ENSURE SUSTAINABLE DEVELOPMENT OF TEXTILE INDUSTRIES
Textiles are an important sector in the South Asian Economies with it accounting for 7.6 % for
China and 17 % of India’s total trade volume [3]
. Also, the SEA (South-East Asian) countries have
high population densities with increasingly stressed water sources. Steps need to be taken urgently
to curb the environmental impact of the textile industries while also securing their future growth
prospects. Political commitment towards reduction and optimization of water consumption and
“Zero Discharge” of all hazardous chemicals is required as a precautionary and preventive measure.
This commitment must be reciprocated with an implementation plan with short term targets, a
dynamic list of hazardous chemicals which need to reduced/eliminated from the process, corporate
will to utilize bio-friendly chemicals/enzymes for processing and community accessible data on
emissions and use of hazardous substances such as Pollutant Release and Transfer Register
3. SUSTAINABLE DEVELOPMENT OF TEXTILE INDUSTRY
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(PRTR) needs to be maintained [4]. These steps are imperative in nature to ensure that we pass on
a healthy environment to future generations and avert the cost of expensive clean-up operations.
3.1.Substituting known Hazardous Chemicals
Many chemicals currently used in textile manufacturing contain carcinogenic amines,
heavy metals or absorbable organic halides other high stress chemicals which rid the water of its
usability. Usage of Petroleum-based synthetic Low Impact Dyes can ensure less water requirement
due to higher than average absorption rate (70-80%). These dyes also do not contain any heavy
metals and the rinse water can be recycled and used again. In the desizing, scouring and bleaching
processes, bio processing offers a low energy, less water and less effluent generating alternative.
For the final wash cycle, instead of using high amount of surfactants, eco-wash laundering system
may be employed which has been proven to be more effective and less damaging to the product
and the environment. [5]
3.2.Alternate Water-Friendly Production Techniques
Processes have been developed to nullify or reduce the toxic release of chemicals in textile
processing. By using bio-enzymes, the process can be made more selective and firms can eliminate
the risk of pollution. Foam processing is increasingly being used in various fields of textile
processing like pre-treatment, dyeing, rinsing, etc. Foam Finishing Technology (FFT) [6] has led
to better color yield, superior levelness, energy savings, minimum wash off and negligible
pollution. Another novel technology is by substituting water by super critical gases in the dyeing
process. Super Critical Fluid Dyeing Technology [7]
increases the color yield of the dye by
recyclability. For soil release and water repellent finishing; Plasma technology [8] offers a chemical
free alternative.
3.3.Water Treatment Processes for Zero Liquid Discharge
A typical dyeing operation involves multiple cycles of water discharge (10-15 in most
cases). All the discharge water is collected in a collection tank and sent to the water treatment plant
which is designed on the influent characteristics and the discharge parameters. The traditional
Effluent treatment plant consists of primary (removal of suspended solids) and secondary
treatment (removal of dissolved and colloidal impurities). To achieve recyclable process water,
effective tertiary treatment is required by processes stated below.
3.3.1. Electro Chemical Processes
These processes are most efficient when concentration of suspended solids or
colloids are not very high. However, they have lower temperature requirements and don’t need
any additional chemical. Also, they prevent the production of unwanted side products which leads
to reduced operational expenses. [9]
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3.3.2. Ion Exchange Method*
The biggest disadvantage of the process is that the resin needs to be recharged after
each cycle for which the process needs to be stopped frequently.
3.3.3. Photo Catalytic Degradation**
Photo Catalysis can decompose a wide range of dyes including highly complex long
chain synthetic dyes (carcinogenic amines).
3.3.4. Multiple Effect Evaporator Unit
i. Evaporation System – Reject stream from the Reverse Osmosis is fed to the vacuum
evaporator (process under vacuum reduces steam consumption) to concentrate up
to 40% solids concentration. The process vapor generated is mixed with steam
using Thermal Vapor Recompression Systems (TVR) to obtain better steam
economy. The condensate recovered has low COD/BOD Concentration and can be
recycled in the plant.
ii. Separation System – The concentrate obtained from the evaporation process is fed
to the thickener and centrifuging system to convert the dissolved salts and
chemicals to solid waste. Under carefully managed conditions, salts used in the
dyeing process may also be recovered from this system and reused. The mother
liquor is recycled back to the evaporator or sent to a solar pond. The water separated
may be recycled back to the plant for dyeing. [12]
3.3.5. Reverse Osmosis
Multiple Stage Reverse Osmosis Systems are used to increase the efficiency of
recovery of permeate from high TDS effluent. More than 80% of the salt and 90% of the color is
rinsed off in the first dye bath. Therefore, by segregating the drain bath, the major portion of the
load is isolated and would enhance the recovery. The industry average for recovery is 80-85 % [13].
This is a highly complex operation which requires a delicate balance of chemical and pressure
conditions and is therefore highly recommended to automate this process to the extent possible.
The concentrated brine can be treated by feeding it to the Multiple Effect Evaporator & Solar
Evaporation or by using one of the emerging technologies such as membrane distillation coupled
with crystallization, electro dialysis and forward osmosis. [14]
4. MATHEMATICAL APPROACH TO OPTIMIZE WATER USAGE & WASTE-WATER
TREATMENT PROBLEM
In industries where zero liquid discharge systems are not feasible, the water consumption and
treatment should be optimized. This can be done by employing a mathematical approach.
*This process removes undesirable anions and cations from effluent. Synthetic Polymeric Ion Exchange Resins exchange
undesirable cations and anions of the waste water with sodium or hydrogen ions of the resin [10].
** Photoactive catalyst illuminates with UV light, which leads to generation of a highly reactive radical [11], which decomposes
organics.
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A Mathematical approach helps develop systematic optimization methods to select process
configurations and operating conditions to develop solutions and strategies to combat these
problems. Similar techniques have been successfully applied in petrochemical industries for the
synthesis of heat exchanger networks. [15]
Mathematically, total mass balance around water using unit gives us:
The pollutant (component) mass balance around the unit gives us:
Combining the two equations for the treatment unit t gives us the following equation:
Similar constraints as above can be placed on concentration and flow rates.
The objective functions can be solved for -
• Minimization of Freshwater Consumption
• Minimization of Waste water generation
• Minimization of number of connections
• Minimization of Network costs
5. CONCLUSION
The global textile supply chain is dynamic & complex, involving many different stakeholders. It
is vital for brands to intervene and phase-out hazardous chemicals throughout their value chains,
starting with those that are known to be highly carcinogenic and that have already been regulated
in the developed countries. This paper has largely dealt with the effect of the textile industry on
water pollution because it is the most prominent and pressing need. However, the effect on air,
noise and land pollution should not be treated lightly. Currently, we consider a BOD to COD ratio
of 1:2 or 1:3 as biodegradable; however, the effluent generated has the ratio in the range of 1:5 to
1:6 [16]. End-of-Pipe treatment is no longer the only requirement to preserve the environment and
Cleaner Production Techniques need to be adopted. Most of these processes also have long term
economic advantages. As decision makers, brands need to take responsibility to restrict the use of
hormone altering and treatment resistant chemicals into our critical waterways, in both textile-
producing and consuming countries. But the biggest onus is on us, the consumer of these products
to purchase from companies adopting environmentally sustainable practices. The consumer needs
to be aware of the impact of the apparels he/she buys because if we don’t change our preferences,
sooner than later we will fail to obtain drinking water even though we might be donning the latest
trends of fashion.
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