2
C. Gutiérrez-Bouzán et al.
1 Introduction
In the last decades, the textile industry has made huge efforts to become more sustainable. It is one of the most important industrial sectors and it uses high amount of
water and chemicals [1, 2]. For this reason, the achievement of a lower environmental
impact is an important goal. On the one side, the production processes have been
improved by using less chemicals o substituting the more hazardous ones by others
less aggressive to the environment. On the other hand, the treatment of wastewater
has been noticeably improved, which is an important contribution because the textile
industry generates up to 20% of industrial wastewater worldwide [3].
Known examples of products substitution by more sustainable ones are, among
others, the use of more biodegradable sizing materials, the non-use of certain azo
dyes, the change of formaldehyde-based finishing by non-allergenic resins, the
replacement of alkylphenols by alcoholethoxylates, the application of more sustainable flame retardants, etc. In addition, all processes have been generally revised and
adapted in order to reduce the consumption of chemicals, energy and water. Thus,
for instance, in the cotton dyeing processes, new types of reactive dyes with lower
salt and water requirements have been developed [4].
As indicated, one of the points that influence the sustainability of the textile
industry is that it is a water-intensive sector. The Ellen MacArthur Foundation
reported that the different processes of the textile industry spent in total about 93
billion cubic metres of water, of which approximately 6 billion cubic metres are
consumed in dyeing and finishing processes [5]. For this reason, different methods
and products to reduce the liquor ratio in the in dyeing, washing and finishing
processes have been developed. This is the case of Avitera reactive dyeing technology
that reduces both water and energy consumption [6].
In any case, the effluents generated in dyeing and washing processes are characterised by a deep colouration due to the unfixed residual dyes, and generally, they have
also a high content of salts as a result of the electrolyte added in the dyeing process.
Due to this salinity, it is not always possible to reduce more the water consumption
in order to accomplish the discharge limits.
On the other hand, the sales of textile products are expected to increase to about
160 million tonnes in 2050; therefore, the amount of discharged wastewater will
also increase significantly [5]. For this reason, the reuse of the treated wastewater is becoming an increasing interest for companies with the aim to reduce the
environmental impact and to achieve the more efficient use of water resources.
This chapter presents the result of our studies to treat and reuse the coloured
effluents of textile industry, which are generally poorly biodegradable. Moreover, the
work is especially focussed on those effluents that have a high content of salts, as it is
the case of reactive dye effluents [7–11]. With this purpose, a coupled electrochemical
and ultraviolet treatment (EC-UV) is used. It is applied to the more coloured and
saline effluents, which are segregated at the end of the dyeing or washing process.
C. Gutiérrez-Bouzán et al.
1 Introduction
In the last decades, the textile industry has made huge efforts to become more sustainable. It is one of the most important industrial sectors and it uses high amount of
water and chemicals [1, 2]. For this reason, the achievement of a lower environmental
impact is an important goal. On the one side, the production processes have been
improved by using less chemicals o substituting the more hazardous ones by others
less aggressive to the environment. On the other hand, the treatment of wastewater
has been noticeably improved, which is an important contribution because the textile
industry generates up to 20% of industrial wastewater worldwide [3].
Known examples of products substitution by more sustainable ones are, among
others, the use of more biodegradable sizing materials, the non-use of certain azo
dyes, the change of formaldehyde-based finishing by non-allergenic resins, the
replacement of alkylphenols by alcoholethoxylates, the application of more sustainable flame retardants, etc. In addition, all processes have been generally revised and
adapted in order to reduce the consumption of chemicals, energy and water. Thus,
for instance, in the cotton dyeing processes, new types of reactive dyes with lower
salt and water requirements have been developed [4].
As indicated, one of the points that influence the sustainability of the textile
industry is that it is a water-intensive sector. The Ellen MacArthur Foundation
reported that the different processes of the textile industry spent in total about 93
billion cubic metres of water, of which approximately 6 billion cubic metres are
consumed in dyeing and finishing processes [5]. For this reason, different methods
and products to reduce the liquor ratio in the in dyeing, washing and finishing
processes have been developed. This is the case of Avitera reactive dyeing technology
that reduces both water and energy consumption [6].
In any case, the effluents generated in dyeing and washing processes are characterised by a deep colouration due to the unfixed residual dyes, and generally, they have
also a high content of salts as a result of the electrolyte added in the dyeing process.
Due to this salinity, it is not always possible to reduce more the water consumption
in order to accomplish the discharge limits.
On the other hand, the sales of textile products are expected to increase to about
160 million tonnes in 2050; therefore, the amount of discharged wastewater will
also increase significantly [5]. For this reason, the reuse of the treated wastewater is becoming an increasing interest for companies with the aim to reduce the
environmental impact and to achieve the more efficient use of water resources.
This chapter presents the result of our studies to treat and reuse the coloured
effluents of textile industry, which are generally poorly biodegradable. Moreover, the
work is especially focussed on those effluents that have a high content of salts, as it is
the case of reactive dye effluents [7–11]. With this purpose, a coupled electrochemical
and ultraviolet treatment (EC-UV) is used. It is applied to the more coloured and
saline effluents, which are segregated at the end of the dyeing or washing process.