«EUROPEAN COMMISSION Integrated Pollution Prevention and Control (IPPC) Reference Document on Best Available Techniques for the Textiles Industry July 2003 ...»
Indirect environmental benefits are associated with the potential savings in energy and chemicals as a result of the improved process control.
The main limitation in the implementation of these expert systems in the textile industry is often the lack of a reliable database.
On-line monitoring Process control by on-line monitoring enhances operation liability in the direction of “right first time production”.
Examples of on-going research in this area are:
· dyeing: the concentration of the COD (related with the dyestuff concentration) is measured on-line during washing and rinsing operations in discontinuous dyeing processes. When the dyestuff concentration in the rinsing bath is negligible, the rinsing process is automatically stopped. This technique allows considerable water and energy savings.
· dyeing and bleaching: by using a special amperometric sensor, the concentration of reducing or oxidising agents on fabrics can be controlled on-line. For example, the completeness of H2O2 removal after bleaching or the concentration of reducing agents in vat dyeing can be monitored and excess use of chemicals avoided.
· dyeing with vat dyes: by monitoring the redox potential, it is possible to detect exactly the point at which the reducing agent is completely rinsed off. When this point is reached the rinsing process can be stopped and the oxidant added to the bath.
Future development of Advanced Oxidation Processes in the textile industry Advanced oxidation processes are already applied in the textile industry (see Section 4.10.7) and further research is under way. The BIOFL-UV project is one example. The aim of this research is to develop and test a waste water treatment based on the UV-activated photolysis of hydrogen peroxide (for the decolouration of the spent bath) combined with a bioflotation process (for the destruction of the residual organic load). The combination of these waste water treatment processes is expected to achieve a complete decolourisation of the process waters for every type of wet process (finishing, bleaching, dyeing, etc.). The project will also develop and implement a process-control software based on artificial neural network and systems dynamics.
The ultimate goal is the recycling, after filtration of 75 % of the process water and dye destruction [313, BIOFL-UV, 2002].
Reed bed systems for waste water treatment
For a long time researchers have pointed out the high removal capacity of natural environments (soil, wet lands, etc.) and have studied the possibility of using such environments (ecosystems) in order to purify, or at least to complete the waste water purification process. Purification techniques that use these principles in constructed plants (artificially reconstructed and confined) are commonly defined as “RBSs” or “constructed wet lands”. These techniques involve the use of plants for waste water treatment, although plants do not always play a primary role in the process. Indeed, the removal of pollutants and the consequent waste water purification are the results of a series of processes which involve reactions and interactions among substratum, micro-organisms and plants.
At present, industrial testing has proven that reed bed techniques and plants can be applied both for the secondary or tertiary treatment of industrial, municipal and zootechnical waste water.
Two textile finishing mills in Italy (Prisma Ricerche in Belluno and Filati di Ziche in the Treviso area) are assessing this technique. In one mill, the waste water coming from the dyehouse (all kind of fibres and dye groups) is treated, after equalisation, in a reed bed system of five tanks in series. It is reported that 90 % COD reduction is achieved [106, Vekos, 2001].
The other company treats the effluent coming from the activated sludge system. This enables a further 51 % reduction of the residual COD [106, Vekos, 2001].
7 CONCLUDING REMARKS
7.1 Timing of the work The work on this BAT Reference document started with a kick-off meeting of the TWG on the 12th and 13th February 1998. A first draft was sent out for consultation to the Technical Working Group in February 2001, then a second draft was issued in November 2001 and the work concluded with a second TWG meeting on 6 - 8 May 2002. After the second TWG meeting there were short consultation periods on the revised parts of Chapter 4 and Chapter 5 and on the new Chapter 6 “Emerging Techniques”, Chapter 7 “Concluding Remarks” and the Executive Summary. Following this consultation the final redrafting took place.
7.2 Source of information Many reports from industry and authorities were elaborated on purpose for the EIPPC Bureau to provide targeted information for the development of the BREF. The reports submitted by Germany [179, UBA, 2001], Spain [180, Spain, 2001], Denmark [192, Danish EPA, 2001], Belgium [18, VITO, 1998] and Euratex [77, EURATEX, 2000] can be considered building blocks for the sections about textile finishing. For the carpet sector information was gathered mainly from GuT ([63, GuT/ ECA, 2000], [171, GuT, 2001]) and ENco [32, ENco, 2001], whereas the wool scouring section is largely based on the document submitted by Interlaine [187, INTERLAINE, 1999]. On many different subjects the contributions provided by VITO were fundamental for refining the information received from other sources and also for ensuring the link with the conclusions reached so far by the OSPAR Forum in the textile sector.
Valuable additional contributions were also received from various players outside the TWG (CRAB - Biella in Italy [193, CRAB, 2001] and Australian representatives [201, Wooltech, 2001] as two examples). Useful information, especially on emission and consumption levels, has also been made available through the participation of IPTS in the European Commission funded project “towards effluent zero” (TOWEFO). The companies involved in the survey as part of the TOWEFO project have collected data supplementing the information provided by the Technical Working Group.
7.3 Level of consensus The exchange information process was successful and a high degree of agreement was reached following the second meeting of the Technical Working Group. No split views were identified
during the final discussion. However, the following points need to be highlighted:
1. Speed of implementation of BAT: the textile industry is a very complex and variegated sector not only in terms of size of the mills, but also in terms of the combination of processes carried out and the possible end-products. The technological level is also very variable ranging from highly automated plants to mills where manual operation is still dominant. The BAT conclusions identified in the BREF represent a good level of environmental ambition, but concerns have been raised by some industry members because of the initial capital investment often required. However, most of the identified BAT are process-integrated techniques, which can deliver cost savings because of improved efficiencies and reduction of waste. The speed of implementation will therefore be a particularly sensitive issue for this industry.
2. Selection of incoming fibre raw material: an important point of discussion concerned the determination as BAT of techniques involving the selection of incoming raw fibre according to environmental criteria.
From the outset, industry put forward strong evidence to show that a large fraction of the pollution load comes from upstream processes. Many techniques have been submitted by the TWG on the available preventive measures and described in Chapter 4. These Textiles Industry 465 Chapter 7 techniques should be part of a general approach in which at each stage of the product’s life cycle the supplier provides information on the type and load of chemicals that are added and that remain on the fibre.
The general principle of this preventive approach is largely accepted. However, objections have been raised by some industry members about the difficulty for the finisher to know what is on the fibre and about the excessive pressure that this approach would put on finishers (especially commission companies) compared to other sectors of the chain.
Mindful of the current difficulties that certain companies may have in controlling/ selecting the source of the fibre raw material, it was recognised that a quality assurance system for incoming textile material is necessary in order to produce an adequate application for an IPPC permit.
It is also evident that the customer is becoming more concerned about the overall environmental impact of the product that he is buying. This is already encouraging brand names (who give their production to commission companies) to ensure that their production satisfies ethical and environmental requirements during the whole production chain, from design to shop-window.
It is consistent with the BAT approach to seek collaboration with upstream partners in the textile chain, not only at a site-specific level, but also at higher levels, such as through trade associations, in order to create a chain of environmental responsibility for textiles.
7.4 Recommendations for future work Limited data was available at the start of the BREF work about the current consumption and emission levels and about the performance of techniques to be considered in the determination of BAT, especially for water effluents. For water emissions, analytical measurements are carried out on the mixed final effluent after the waste water treatment plant (when this exists), but such data is not useful for the needs of the BREF.
A big effort has been made by some members of the TWG to carry out surveys and analytical campaigns in selected textile mills and thanks to the results of this work the base of data reported in this document is already of high value. Nevertheless, for future BREF reviews, all TWG and interested parties should continue, or start, to collect data for the most problematic processes, with the aim of assessing as far as possible the relationship between the environmental performance of the process and the technology and chemicals used. Initiatives and research projects should also be encouraged with this purpose.
In the future it is also envisaged that more data should come from the application of a systematic monitoring of inputs and outputs at process-specific level at the textile mills.
Another general remark for future work concerns economic data. In some cases the information received was too vague to allow a precise balance of the costs and savings involved. In future more extensive data about costs and savings could be beneficial in assisting the determination of BAT.
Apart from these general considerations, specific areas where data and information are missing
are the following:
· biological treatment techniques for wool scouring water effluents: performance data are missing · scouring of extra-fine wool: specific consumption and emission levels reported in the BREF are not in relation with the technology used and could not be used to reach conclusions on BAT-associated values · functional finishing: in Chapter 4 a number of techniques have been described for easy-care, mothproofing and softening treatments. However, little information was provided about techniques to be considered in the determination of BAT for other functional finishing treatments 466 Textiles Industry
Chapter 7· carpet sector (excluding carpet yarn wet processing): except for air emissions, very little data has been supplied on consumption and emission levels for wet processes (e.g. dyeing, printing, etc.) · silk, flax and linen: very little information has been provided in general about these fibres · industry-specific monitoring aspects.
7.5 Suggested topics for future R & D projects
The following might be considered for future Research and Development projects:
Knowledge/ monitoring of the process · techniques to improve on-line monitoring and understanding of the process: at present textile process parameters are often set more on the basis of human experience than on a real physical/chemical basis · there are two connected data problems for proprietary chemicals and auxiliaries used in the
textile sector that hinder the selection of the most environmentally-sound options:
§ readily-comparable environmental data § information on single components, main impurities and by-products present in formulations.
There are obvious commercial confidentiality problems, but this should not prevent further dialogue and development.
Specific processes/ treatments · desizing: weaving and desizing at the same mill, with the aim of allowing a more extensive application of size recovery · membrane techniques: treatability studies of single defined and segregated waste water streams by membrane techniques with assessment of the chemical compounds causing scaling/fouling or damage to the membranes · pesticides: some pesticides are naturally degraded by UV light. The use of artificial UV light to accelerate this degradation in opened fleeces is a technique that warrants further work · spin finishing agents for man-made fibres: despite recent improvement in this field, further work is necessary to develop alternative compounds easy to remove and with reduced environmental impact both on water and air.
Waste water · waste water streams containing a significant non-biodegradable fraction should be treated by adequate techniques, before or instead of final biological treatment: R&D is needed to improve techniques for segregating such streams as close as possible to their point of production to maximise effective recovery or targeted treatment · effluents from the textile industry are complex mixtures of organic and inorganic substances. In most cases, the acute toxicity to test organisms is reduced dramatically by biological treatment. The environmental impact of such mixed effluents, with possible synergistic effects of components, remains difficult to ascertain. Work is needed in two
§ the continuing development of Direct Toxicity Assessment (DTA) on mixed effluents § the identification of compounds with residual (sometimes high) toxicity after treatment(s).
The EC is launching and supporting, through its RTD programmes, a series of projects dealing with clean technologies, emerging effluent treatment and recycling technologies and management strategies.
Among these projects, there are some dealing with:
1) development of ultrasonic and laser technologies to replace the traditional scouring of wool;
2) development of plasma technologies (use of gases instead of liquids for chemical treatments) for the finishing of textiles;
3) development of new enzyme-based processes for wool-felting processing, covering the whole chain from carbonisation (replacing sulphuric acid with enzymes) to final felting;
4) development of supercritical fluids for dyeing.
In particular, the EC supports research on harmful properties on dyes used in textile industry, especially by SMEs. Most of these dyes are "existing substances", thus not having been tested for any harmful effects. Dyes widely used in textile industry are being tested for their mutagenic effects. When possible, substitutes are identified.
Potentially these projects could provide a useful contribution to future BREF reviews. Readers are therefore invited to inform the EIPPCB of any research results which are relevant to the scope of this document (see also the preface of this document).
REFERENCES 3 RIZA, (1998). "Dutch notes on BAT for the textile and carpet industry",.
4 Tebodin, (1991). "Technical and economic aspects of measures to reduce water pollution from the textile finishing industry",.
5 OSPAR (1994). "PARCOM Recommendation 94/5 concerning Best Available Techniques and Best Environmental Practice for Wet Processes in the Textile Processing Industry".
7 UBA, (1994). "Reduction of Waste Water in the Textile Industry", Texte 3/94.
8 Danish EPA, (1997). "Environmental Assessment of Textiles", Environmental project n. 369.