Water Consumption in Textile Processing Industry

Last Updated on 03/02/2021

Water Consumption in Textile Industry:

Water is used extensively throughout textile processing operations. Almost all dyes, specialty chemicals, and finishing chemicals are applied to textile substrates from water baths. In addition, most fabric preparation steps, including desizing, scouring, bleaching, and mercerizing, use aqueous systems.

Each textile process utilizes a large amount of water, which will finally become wastewater. The most significant sources of pollution among various process stages are pretreatment, dyeing, printing, and finishing of textile materials.

Desizing is the industry’s largest source of pollution. During desizing, all the sizes used during weaving are removed from the fabric and discarded into the wastewater. In scouring, dirt, oil, and waxes from natural fibers are removed from the fabric and washed into wastewater stream. Normally, desizing and scouring are combined and these two processes may contribute to 50% of BOD in the wastewater in the wet processing.

Factors of water consumption in textile processing industry:
Water consumption in textile industry is related to many factors, including:

Type of fiber and specific operations performed;
Mill size;
Type and age of equipment; and
Type of operation (batch, semi–continuous, continuous).

On average, 90–95% of the water used by the factory ends up as effluent. The only losses are due to steam production and evaporation from hot baths, dyeing and drying operations. The largest water use generally refers to cotton products; synthetic fibers, wool and silk require lower water volumes per unit of product.

The amount of water used varies widely in the industry, depending on specific processes operated at the mill, equipment used, and prevailing management philosophy concerning water use.

Textile operations vary greatly in water consumption. Below Figure summarizes the water consumption of various types of operations in textile processing industry. Wool and felted fabrics processes are more water intensive than other processing subcategories such as wovens, knits, stock, and carpet.

Figure: Water Consumption in Textile Industry

Water use can vary widely between similar operations as well. For example, knit mills average 10 gallons of water per pound of production, yet water use ranges from a low of 2.5 gallons to a high of 45.2 gallons.

Textile industry is a leading consumer of water and it ranks among ten top water consuming industries. Table-1 shows the approximate consumption of water for the processing of various textile fibres.

Table-1: Water Consumption by Textile Industry in Various Processes

Substrate …………………Water consumption (kg/kg of fabric)

Cotton …………………250-350
Wool …………………..200-300
Nylon ………………….125-150
Rayon …………………125-150
Polyester ………………100-200
Acrylic …………………100-200

Cotton fibres require the largest amount of water for its preparation. In general, the water consumption in a process house is about three times the consumption of all other units put together (Table-2). The water consumption in the bleaching section is highest.

Table-2: Water Consumption Pattern in Textile Mills

Process ……………………………Water consumption (% of total)

Bleaching, Finishing ……………38
Dyeing ………………………16
Printing ……………………….8
Boiler House …………………14
Humidification (spinning) ………6
Humidification (weaving)……… 9
Sanitary, Domestic etc……….. 9

Water consumption in continuous dyeing is much lower and hence a much smaller membrane area is needed to remove dye from a more concentrated waste stream.

Water consumption for exhaust dyeing of cellulose with direct dyes is much less than for reactive dyes and recycling possibilities are likely to be easier to realize. This is because exhaust processes generally use much less salt, require no fixation alkali and achieve desired levels of wet fastness by special after treatments.

The conventional preparatory processes of textiles namely, desizing, scouring, bleaching, and washing are highly water consuming operations and consequently energy-intensive (Table-3).

Table-3: Consumption of Water and Energy in Kiers and J-Box Processes

Process ……Consumption of water 1/kg……Consumption of steam kg/kg (J-Box Processes)

Desizing …………………………3 …………………..….0.25
Washing ……………………….20 …………………..…0.35
Scouring ………………………2 ………………………..1.75
Washing ………………………..20 …………………..…0.30
Bleaching ………………………2 ……………………….1.00
Washing ……………………….40 ……………………….0.60
Total ……………………………87 ……………………..4.20

Conventional kier-boiling …100 ……………………….5.10

Textile industry generally needs to find ways to reduce its water consumption. As a major user and potential polluter of water, the textile wet processing industry is under particular pressure to reduce water consumption on both environmental and economic grounds. Securing a reliable and economic supply of water is now a strategic imperative for textile operations.

It is more important to minimize specific water consumption and specific wastewater flow, respectively. It is even more important to prevent and minimize wastewater pollution by process-integrated and production-integrated measures.

References:

Water recycling in textile wet processing by Edited by J Kenneth Skelly
Characterization and Treatment of Textile Wastewater by Himanshu Patel and R.T. Vashi
Theory and Practice of Water and Wastewater Treatment By Ronald Droste and Ronald Gehr

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Mazharul Islam Kiron

Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. He is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.