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P. S. Kumar et al.
wasted in the process. Though its volume is not considerably large (i.e., less grey
water volume), however, it has high levels of COD, BOD, and SS which pollutes the
environment. Another important operation that comes in this category is the printing
process. The specific water consumption of this process lies in the range of 8–16
L/kg of the product. In this process, water is used to wash off the colorants added
in specific locations, according to the design pattern. The amount of water used for
printing is very less compared to that of dyeing. However, the colorants used in this
process contaminates water with high levels of COD and TSS.
13.4 Wet Processing Unit
As the name suggests the wet processing unit utilizes large amounts of water, majorly
for rinsing the fabric after chemical treatment. Also, water consumption varies widely
with the equipment used to carry out the process. For example, the water requirement
for a batch processing unit is proportional to the bath ratio and other characteristics
such as mixing, agitation, and the turnover rate of fabric [30]. In general, the wet
processing unit comprises pretreatment, dyeing, and, finishing operations that are
specific to the type of fabric used. Therefore, the basis of the classification of the
water footprint of the cotton textile industry is built on the different methods of fabric
production. The basic steps involved in the wet processing stage of woven and knitted
fabric is shown in Fig. 9. The major footprints: blue and grey water footprints for
each of these fabrics are compared and discussed in detail in the following section.
14 Blue Water Footprint in Textile Industrial Processes
The blue water footprint of the fabric processing unit is described in Fig. 8. It is evident
from the figure that the dyeing operation utilizes a tremendous amount of water
compared to the other processes. The desizing and bleaching operations consume
water in the range of 2.5–25 L/kg fabric. Scouring and Mercerization consume water
in the range of 20–45 and 17–32 L/kg fabric. Dyeing requires water in the range of 10–
300 L/kg of the product. The reason for the range to be larger is because the water
requirement varies according to the chemical used for dyeing and the machinery
assigned to perform the dyeing operation. The water requirement of some of the
dyeing equipment is listed in Table 2.
The specific water consumption for dyeing of the woven fabric process is found to
be in the range of 130–150 L/kg of dyed fabric. While for the knitted fabric process,
it is found to be in the range of 110–130 L/kg of dyed fabric. The woven fabric
has a higher water footprint than the knitted fabric due to additional pretreatment
operations involved in the wet processing unit as described in Fig. 9. This highwater consumption will reflect in the environment in the form of grey water which
is released as effluent from each of the individual processes.
P. S. Kumar et al.
wasted in the process. Though its volume is not considerably large (i.e., less grey
water volume), however, it has high levels of COD, BOD, and SS which pollutes the
environment. Another important operation that comes in this category is the printing
process. The specific water consumption of this process lies in the range of 8–16
L/kg of the product. In this process, water is used to wash off the colorants added
in specific locations, according to the design pattern. The amount of water used for
printing is very less compared to that of dyeing. However, the colorants used in this
process contaminates water with high levels of COD and TSS.
13.4 Wet Processing Unit
As the name suggests the wet processing unit utilizes large amounts of water, majorly
for rinsing the fabric after chemical treatment. Also, water consumption varies widely
with the equipment used to carry out the process. For example, the water requirement
for a batch processing unit is proportional to the bath ratio and other characteristics
such as mixing, agitation, and the turnover rate of fabric [30]. In general, the wet
processing unit comprises pretreatment, dyeing, and, finishing operations that are
specific to the type of fabric used. Therefore, the basis of the classification of the
water footprint of the cotton textile industry is built on the different methods of fabric
production. The basic steps involved in the wet processing stage of woven and knitted
fabric is shown in Fig. 9. The major footprints: blue and grey water footprints for
each of these fabrics are compared and discussed in detail in the following section.
14 Blue Water Footprint in Textile Industrial Processes
The blue water footprint of the fabric processing unit is described in Fig. 8. It is evident
from the figure that the dyeing operation utilizes a tremendous amount of water
compared to the other processes. The desizing and bleaching operations consume
water in the range of 2.5–25 L/kg fabric. Scouring and Mercerization consume water
in the range of 20–45 and 17–32 L/kg fabric. Dyeing requires water in the range of 10–
300 L/kg of the product. The reason for the range to be larger is because the water
requirement varies according to the chemical used for dyeing and the machinery
assigned to perform the dyeing operation. The water requirement of some of the
dyeing equipment is listed in Table 2.
The specific water consumption for dyeing of the woven fabric process is found to
be in the range of 130–150 L/kg of dyed fabric. While for the knitted fabric process,
it is found to be in the range of 110–130 L/kg of dyed fabric. The woven fabric
has a higher water footprint than the knitted fabric due to additional pretreatment
operations involved in the wet processing unit as described in Fig. 9. This highwater consumption will reflect in the environment in the form of grey water which
is released as effluent from each of the individual processes.