«EUROPEAN COMMISSION Integrated Pollution Prevention and Control (IPPC) Reference Document on Best Available Techniques for the Textiles Industry July 2003 ...»
The concept of “levels associated with BAT” described above is to be distinguished from the term “achievable level” used elsewhere in this document. Where a level is described as “achievable” using a particular technique or combination of techniques, this should be understood to mean that the level may be expected to be achieved over a substantial period of time in a well maintained and operated installation or process using those techniques.
Where available, data concerning costs have been given together with the description of the techniques presented in the previous chapter. These give a rough indication about the magnitude of costs involved. However, the actual cost of applying a technique will depend strongly on the specific situation regarding, for example, taxes, fees, and the technical characteristics of the installation concerned. It is not possible to evaluate such site-specific factors fully in this document. In the absence of data concerning costs, conclusions on economic viability of techniques are drawn from observations on existing installations.
It is intended that the general BAT in this chapter are a reference point against which to judge the current performance of an existing installation or to judge a proposal for a new installation.
In this way they will assist in the determination of appropriate "BAT-based" conditions for the Textiles Industry 445 Chapter 5 installation or in the establishment of general binding rules under Article 9(8). It is foreseen that new installations can be designed to perform at or even better than the general BAT levels presented here. It is also considered that existing installations could move towards the general BAT levels or do better, subject to the technical and economic applicability of the techniques in each case.
While the BAT reference documents do not set legally binding standards, they are meant to give information for the guidance of industry, Member States and the public on achievable emission and consumption levels when using specified techniques. The appropriate limit values for any specific case will need to be determined taking into account the objectives of the IPPC Directive and the local considerations.
5.1 Generic BAT (whole textile industry) The textile industry is a fragmented and heterogeneous sector, composed of a wide number of sub-sectors. The nature of waste generated depends on the type of textile facility, the processes being operated and the fibres used. Despite this complexity, a number of techniques can be defined as general BAT applicable to all types of textile operations, regardless of the processes they use or the products they produce.
Technology by itself is not sufficient; it needs to go together with environmental management and good housekeeping. Management of an installation that uses potentially polluting processes requires the implementation of many of the elements of an Environmental Management System (EMS).
BAT is to:
· implement environmental awareness and include it in training programmes · apply good practices for maintenance and cleaning (see 4.1.1) · store each chemical according to the instructions given by the manufacturer in the Material Safety Data Sheets and follow the indications given in the horizontal BREF on Storage (in preparation at the time of writing) · put in place measures to avoid spillage of chemicals and process liquors. If spillage does occur, containment procedures must be available as well as a means of cleaning up and disposing of the spillage safely. It should be impossible for spillage to enter surface waters or sewer · implement a monitoring system for process inputs and outputs (both on-site and on-process level), including inputs of textile raw material, chemicals, heat, power and water, and outputs of product, waste water, air emissions, sludges, solid wastes and by-products. A good knowledge of the process inputs and outputs is a prerequisite for identifying priority areas and options for improving environmental performance.
Dosing and dispensing of chemicals (excluding dyes)
BAT is to install automated dosing and dispensing systems which meter the exact amounts of chemicals and auxiliaries required and deliver them directly to the various machines through pipework without human contact. The water used for washing the preparation vessel and supply pipes is taken into account when the quantity of prepared liquor is calculated. Other systems use individual streams for each of the products to be delivered. In this way the chemicals are not premixed before being introduced into the applicator or machine and there is no need to clean containers, pumps and pipes before the next step. More information about automated dosing and dispensing systems is given in Section 4.1.3.
Selection & use of chemicals
BAT is to follow certain general principles in selecting chemicals and managing their use:
· where it is possible to achieve the desired process result without the use of chemicals, then avoid their use altogether · where this is not possible, adopt a risk-based approach to selecting chemicals and their utilisation mode in order to ensure the lowest overall environmental risk.
There are a number of lists and classification tools for chemicals. Some examples of tools for selecting/ assessing chemicals, according to their relevance to water and air impact are described in Sections 4.3.1 and 4.3.2. Modes of operation that ensure the lowest overall risk include techniques such as closed-loops and the in-loop destruction of pollutants. Of course, it is essential that due recognition be given to relevant Community legislation.
Following these principles, a number of detailed BAT conclusions arise. These are listed below.
For surfactants BAT is to substitute alkylphenol ethoxylates and other hazardous surfactants with susbtitutes that are readily biodegradable or bioeliminable in the waste water treatment plant and do not form toxic metabolites (as described in Section 4.3.3).
For complexing agents BAT is to:
· avoid or reduce the use of complexing agent in pretreatment and dyeing processes by a
Ø softening of fresh water to remove the iron and the hardening alkaline-earth cations from the process water Ø using a dry process to remove coarse iron particles from the fabric before bleaching (magnetic detectors are installed on continuous pretreatment lines as described in Section 4.5.6). This treatment is convenient when the process starts with an oxidative/desizing step, otherwise a huge amount of chemicals would be required to dissolve the coarse iron particles in a wet process. However, this step is not necessary when an alkaline scouring treatment is carried out as a first step before bleaching Ø removing the iron that is inside the fibre using acid demineralisation, or better, nonhazardous reductive agents (see Section 4.5.6), before bleaching heavily contaminated fabrics Ø applying hydrogen peroxide under optimal controlled conditions as described in Section 4.5.6 · select biodegradable or bioeliminable complexing agents (as described in Section 4.3.4).
For antifoaming agents BAT is to:
· minimise or avoid their use by:
Ø using bath-less air-jets, where the liquor is not agitated by fabric rotation Ø re-using treated bath · select anti-foaming agents that are free from mineral oils and that are characterised by high bioelimination rates, as described in Section 4.3.5.
Selection of incoming fibre raw material
At present, textile manufacturers are not well informed by their suppliers about the quality and quantity of substances (e.g. preparation agents, pesticides, knitting oils) applied on the fibre during the upstream processes. Knowledge of these characteristics is essential to enable the manufacturer to prevent and control the environmental impact resulting from these substances.
BAT is to seek collaboration with upstream partners in the textile chain in order to create a chain of environmental responsibility for textiles. It is desirable to exchange information on the type and load of chemicals that are added and remain on the fibre at each stage of the product’s life cycle. Besides specific contract conditions, a number of schemes exist such as the organic certification for cotton, the certification scheme applied in Germany for garments, etc. The table Textiles Industry 447 Chapter 5 below lists the BAT identified for a some raw materials for preventing at source the environmental impact arising from pollutants present on the fibre before it enters the finishing process. All measures assume that the fibre raw materials to textile processing are produced with some sort of quality assurance scheme so that the finisher can get the appropriate information about the types and amounts of contaminants.
Table 5.1: BAT for selection of incoming fibre raw material Water & energy management Water and energy savings are often related in the textile industry because the main use of energy is to heat up the process baths.
The following is a summary of the selected BAT for water and energy saving. The limitations in the applicability of the listed techniques are discussed in the cross-referenced sections.
BAT is to:
· monitor water & energy consumption in the various processes, as mentioned earlier and described in Section 4.1.2 · install flow control devices and automatic stop valves on continuous machinery (Sections 4.1.4 and 4.9.2) · install automatic controllers for control of fill volume and liquor temperature in batch machines (Sections 4.1.1 and 4.6.19) · establish well-documented production procedures in order to avoid wastage of resources from inappropriate work practices (Section 4.1.4) · optimise scheduling in production and adjust processes in pretreatment to quality requirements in downstream processes (Section 4.1.1) · investigate the possibility of combining different treatments in one single step (Sections 4.1.1 and 4.1.4) · install low- and ultra-low liquor ratio machinery in batch processes (Sections 4.6.19 to 4.6.21) · introduce low add-on application techniques in continuous processes (Section 4.1.4) · improve washing efficiency in both batch and continuous processing, as described in Sections 4.9.1 and 4.9.2 · re-use cooling water as process water (also allowing heat recovery) (Section 4.1.1) 448 Textiles Industry
Chapter 5· investigate possibilities for water re-use and recycling by systematic characterisation of quality and volume of the various process streams in order to identify processes for which the substances contained in the various waste streams are still valuable and/or do not interfere with the quality of the product. For recycling purposes in batch processes it is convenient to install machinery with built-in features that facilitate recovery and re-use of waste streams. Examples of options for water re-use are reported in Sections 4.5.8 and 4.6.22 · fit hoods and covers ensuring full closure of machinery that could give rise to vapour losses (Sections 4.1.1 and 4.6.19) · insulate pipes, valves, tanks, machines to minimise heat losses (Section 4.1.5) · optimise boiler houses by applying re-use of condensed water, preheating of air supply, heat recovery from combustion gases (Sections 4.1.1, 4.4.3 and 4.8.1) · segregate hot and cold waste water streams prior to heat recovery and recover heat from the hot stream (Sections 4.1.1 and 4.6.22) · install heat recovery systems for off-gases (Sections 4.1.1, 4.4.3 and 4.8.1) · install frequency-controlled electric motors (Section 4.1.1).
Management of waste streams
BAT is to:
· collect separately unavoidable solid waste · use bulk or returnable containers.
5.2 Process-integrated measures for unit processes and operations This section presents process-integrated measures for processes and operations covered in this document. End-of-pipe abatement measures are described in the next section. The presentation follows a unit process-basis approach indicating, where necessary, the sectors/categories of mills where there are limitations in the applicability of the specific measure discussed.
5.2.1 Wool scouring Wool scouring can be done using water (most common situation) or organic solvent. Both methods are determined as BAT, provided that a number of requirements are satisfied.
Wool scouring with water
BAT is to:
· select raw wool fibre according to the BAT measures identified in Table 5.1 · substitute alkylphenol ethoxylates detergents with alcohol ethoxylates or other readily biodegradable substitutes that do not give rise to toxic metabolites, according to the BAT measures defined in Section 4.3.3 · use dirt removal / grease recovery loops of high capacity as described in Section 4.4.1 (for fine and extra-fine wool, the wool grease recovery loop, when carried out using machinery that has a separate continuous sludge flow output, also allows the elimination of the very fine dirt fraction, without the need for a separate loop for dirt removal). BAT-associated values for water consumption are 2 to 4 l/kg of greasy wool for medium and large mills (processing 15000 tonnes/year of greasy wool) and 6 l/kg for small mills. Associated values for grease recovery range between 25 and 30 % of the grease estimated to be present in the wool scoured · reduce energy consumption to 4 - 4.5 MJ/kg greasy wool processed, comprising approximately 3.5 MJ/kg thermal energy and 1 MJ/kg electrical energy by a suitable combination of the following techniques (in addition to the grease recovery loop mentioned
Textiles Industry 449 Chapter 5 Ø fitting covers to scour bowls to prevent heat losses Ø optimising the performance of the final squeeze press in order to improve mechanical removal of water before the drying process Ø runnning the last bowl at relatively high temperature. Optimum temperature is shown to be 65°C, except when peroxide bleaching is carried out in the last bowl. In this case the optimum bleaching temperature is 48°C Ø controlling automatically the humidity in the dryer via sensors which measure the humidity of the dryer atmosphere or of the wool itself Ø retrofittting heat recovery units to dryers.
Due to the lack of data it is not possible to define whether the above-mentioned BAT associated values for water and energy consumption are also applicable to extra-fine wool (fibre diameter typically less than 20µm).
Scouring with organic solvent Scouring with organic solvent is determined as BAT, provided that all measures described in Section 18.104.22.168 are taken to minimise fugitive losses and prevent any possible contamination of groundwater arising from diffuse pollution and accidents.
5.2.2 Textile finishing and carpet industry
PRETREATMENTRemoving knitting lubricants from fabric
BAT is to do one of following:
· select knitted fabric that has been processed using water-soluble and biodegradable lubricants instead of the conventional mineral oil-based lubricants (see Section 4.2.3).
Remove them by water washing. With knitted fabrics made of synthetic fibres the washing step needs to be carried out before thermofixation (to remove the lubricants and avoid them being released in the form of air emissions) · carry out the thermofixation step before washing and treat the air emissions generated from the stenter frame by dry electrofiltration systems that allow energy recovery and separate collection of the oil. This will reduce the contamination of the effluent (see Section 4.10.9) · remove the non-water soluble oils using organic solvent washing. The requirements described in Section 4.9.3 are then taken, along with provisions for the in-loop destruction of the persistent pollutants (e.g. by advanced oxidation processes). This will avoid any possible contamination of groundwater arising from diffuse pollution and accidents. This technique is convenient when other non water-soluble preparation agents, such as silicone oils, are present on the fabric.
BAT is to do one of the following: