Everyone in the textile industry knows that a lot of water is used to produce fabric. If you consider just the fabric processing stages, water is used in 3 main areas including; Pre-cleaning and rinsing of fabric or yarn before dyeing or printing; Dyeing, printing, soaping and the after-treatment and; Rinsing.
Before the fabric is even processed, a lot of water has already been consumed. But how much specifically is used? Let’s put a few numbers on the table:
The global textile industry is said to consume 2 trillion gallons of water
The textile mill industry in the U.S. produces 135 billion gallons of discharge water each year
The textile industry in India uses 425 Million gallons of water a day
Cotton consumes 2.6% of global water usage annually
An average textile mill with a production of 8 tons of fabric a day uses about 1.6 million litres or 422,675 gallons per day
Depending on the dye used, 30-50 litres of water are used per kg
Water used in dyeing yarn is at approximately 60 litres per kg of yarn
As you can see, these numbers are huge and even if the numbers may not be consistent depending on the study or research you point at, the fact remains that, the mammoth amount of water used in the textile industry is competing with the growing water needs of the rest of nature and humanity.
Use of dyes in fabrics
Whether you look at natural fibres (e.g. cotton or wool) or synthetic fibres (e.g. polyester and nylon), dyeing is a water-consuming part of the process.
If you consider the two basic stages of textile production: fibre production and weaving into cloth.
The production of fibre takes little to no water for synthetics while for natural fibres like cotton, enormous amounts of water are used.
For the weaving fibre into cloth process, both synthetic and organic fibres use the same types of dyes as well as the same amount of water used in the dyeing process.
The Dyeing process involves the use of varying grades of dyestuffs such as – dyeing agents, Disperse Dyes (Polyester), Vat Dyes (Viscose), Sulphur Dyes, Reactive Dyes, dispersants and solubalisers, soaping and levelling agents.
This is important to note because dyeing not only uses copious amounts of water, but also has the capacity to contaminate water bodies when not correctly disposed.
Effects and dangers of textile dyeing on water systems
On average, dyeing accounts for 15%-20% of all the waste water flow in textile production. Most of these chemicals end up in water effluent. According to the World Bank, almost 20% of global industrial water pollution comes from dyeing and treatment of textiles and ‘Some 72 toxic chemicals reach our water supply from textile dyeing’.
Another study shows that up to 200,000 tons of dyes are lost to effluents every year during the dyeing and finishing processes. These dyes escape from conventional waste water treatment processes and make their way to water systems. It is therefore no surprise that the textile industry is considered to be the most polluting of all industrial sectors.
Some of the effects of the textile dye effluents on water systems include:
Oily scum and colours cause bad smell and bad appearance on water systems
Interfere with photosynthesis by blocking the penetration of sunlight
Oxygen depletion for marine life
Clogs soil pores and thus reduces soil fertility
Hardens soil causing difficulty in root penetration
Polluted water allows breeding of bacteria and viruses
Carcinogen from colorants containing organically bound chlorine
Practical solutions to the problem
There are basically two ways for the water pollution problem caused by dyes in textile industry to be faced; one is through better management (or better operation, maintenance and procedures) and the second is through using better technical options.
The core objective of both these options would be to :
reduce water consumption by reducing the number of steps in the process as well as recycling water within the process.reduce chemical consumption by substituting harmful chemicals and finding processes to reduce chemical use.reduce the impact of dyes on water bodies by using dyes with lower toxicity, promoting natural dyes and using more water efficacious processes.
References:
Most of the information, data and statistics in this article has been sourced from: