Overview of the effect of environmental legislation on the UK textile wet processing industry

Peter Cooper Courtaulds Textiles, PO Box 54, Haydn Road, Nottingham NGS 1 DH, UK

INTRODUCTION To understand the effect of environmental legislation on the textile wet processing industry it is necessary to consider the statutory framework prior to recent legisla- tion in the UK and the effect of EC directives. Therefore my presentation will: (a) Describe and evaluate the consent system and its

(b) Investigate the pollution load produced by the textile

(c) Explain new legislation and regulation (d) Draw conclusions about the consequences, both

threats and opportunities, for the textile wet process- ing industry.

effectiveness prior to 1988

wet processing industry

CONTROL OF EFFLUENT Waste water discharges in the UK can be split into two distinct categories, those discharging to sewer, which are then treated by municipal sewage treatment works, and those discharging direct to water courses (rivers, streams). As the majority of textile wet processors discharge to sewer I will concentrate on the system controlling these discharges, but it should be understood that direct dis- charges are under similar control, albeit the control pa- rameters are much stricter.

Drainage of trade premises to sewer has been control- led since 1937 by the Drainage of Trade Premises Act, with some notable amendments in 1961 and 1974. The 1937 act gave control of trade effluent discharges to the local authorities but this was changed in the 1974 act to give control to the newly formed (1973) regional water authorities. Thus from 1974 to 1988 each regional water authority was responsible for control and management of both potable and foul (waste) water.

The aims of this effluent control system were various, but included: (a) Preventing discharges having harmful effects on the

(b) Ensuring the disposal of sewage meets discharge

(c) Preventing interference with the effective workmg

environment

standards

and economic operation of treatment works.

The system, which is still widely operational, allows discharge of industrial effluent with the consent of the water authority; otherwise an offence is committed and

the person responsible can be fined. Trade effluent is defined as ‘any liquid, with or without particles in sus- pension, which is produced ... in the course of any indus- try process.’

The licence (called a ’consent’) to discharge to sewer under this system contains conditions covering: (a)The composition, volume and rate of discharge of

(b) Its temperature, acidity and alkalinity (c) Elimination or reduction of any specified substance

that might make treatment especially difficult or ex- pensive

trade effluent

(d) Timing, monitoring and the basis of charging.

In practice, this system specifically bans from dis- charges the substances quoted below: - Petroleum spirit - Calcium carbide - Cyanides, cyanogen compounds producing HCN - Carbon disulphide - Mercury and its compounds - Cadmium and its compounds - Organohalogen compounds.

Of particular relevance to the textile industry are carbon disulphide, mercury as a contaminant in inorganic prod- ucts and organohalogen compounds used as solvents and degreasers. The system limits, to a maximum con- centration, most of or all the parameters listed below: - PH - COD - Suspended solids - Heavyhoxic metals - Sulphate - Grease and oil - Anionic detergents - Ammoniacal nitrogen - Sulphide, hydrosulphide, etc.

The toxicheavy-metal category is large, including ar- senic, beryllium, chromium, copper, lead, nickel and zinc. Most of the parameters, particularly pH, COD, metal, sulphate, detergents, sulphides and nitrogen are relevant to the textile industry. Control strategies, in- cluding neutralising pH, balancing and COD control are therefore in use, but control generally tends to be at or towards the limits of consent.

176 JSDC VOLUME 108 APRIL 1992

On the face of it, therefore, this is a fairly wide-ranging pollution control system. However, the inability of this system to function effectively (the so called poacher- gamekeeper role of the water authorities) was a major reason for the changes introduced recently, which are discussed further below. But how relevant has this inef- fectiveness been to textile wet processing? Can the sector pollute the environment through its process emissions and if so, how significantly?

The perception of the general observer is that it does, as shown in Figure 1. More detailed investigation of raw materials, processes and products may help to determine how accurate this perception is. The industry's products, both fabrics and garments, made from natural fibres (cotton, wool, etc.) and regenerated cellulosics biodegrade effectively. Polyester, nylon, polypropylene and acrylics are persistent, constitute a threat and account for some 65% of total fibre usage in textiles.

High

>105 C 0 r - -0-

5 Med.

z E

5 4 0 5

-0

c

Low

Kev

I I

Low Med. High

Water pollution

I Electricity 5 Paper and pulp 9 Electronics 2 Food and drink 6 Metal manufacture 10 Chemicals and 3 Synthetic fibres 7 Oil refining textiles 4 Rubber 8 Leather 11 Metal fabrication

Figure 1 Water demand/pollution matrix (sizes of circles provide an indication of the respective sizes of the various industry sectors) (Source: Ecotec Research and Consulting Ltd)

Viscose fibres and fabrics could claim to be environ- mentally acceptable as they are made from a renewable source (trees) and are readily biodegradeable as final products. However, the process involves use of carbon disulphide, sulphuric acid and zinc compounds which are tightly controlled in production, but all could have a significant environmental impact.

Characterisation of some of the typical chemicals and products used in textile processes using a pollution cat- egory range of 1 to 5 (1 being the least harmful and 5 being the most harmful), as shown in Table 1, indicates that the industry uses products from across the whole range of pollution capability.

Table 1 Pollution capability of some of the chemicaMproducts used in the textile industry (Source: ICI Specialties)

General chemical Difficulty of Pollution type treatment category

Alkalis Mineral acids Natural salts Oxidising agents

Starch sizes Vegetable oils, fats

and waxes Biodegradable surfactants

Organic acids Reducing agents

Dyes and fluorescent

Fibres and polymeric

Polyacrylate sizes Synthetic polymer finishes

Silicones

brighteners

impurities

Wool grease PVA sizes Starch ethers and

esters Mineral oil Surfactant resistant to biodegradation

Anionic and non-ionic softeners

Formaldehyde and N-methylol reactants

Chlorinated solvents and carriers

Cationic retarders and softeners

Biocides Sequestering agents Heavy-metal salts

Relatively harmless 1 inorganic pollutants

Readily biodegradable 2 moderate-high BOD

Dyes and polymers 3 difficult to biodegrade

Difficult to biodegrade

Moderate BOD

Unsuitable for conventional biological treatment

Negligible BOD

4

5

The inorganic and organic acids, oxidising and reducing agents, alkalis and starches and waxes used are relatively harmless pollutants and/or readily biodegradeable. Of course high concentrations of the acids, alkalis, and re- ducing and oxidising agents can have significant envir- onmental impact if an uncontrolled spill occurs.

The dyes used are difficult to biodegrade and some, particularly hydrolysed reactives and certain acids, are not readily absorbed by active sludge, and therefore pass through the treatment works into rivers and streams. Those that do this are not thought to have a significant long-term effect, but coloured rivers are not acceptable.

Some dyes and auxiliaries contain heavy metals such as copper, zinc and chromium that are not totally ex- hausted onto the fibre. When these are discharged they clearly do have an environmental impact. The discharg- ing of baths containing any number of the products in categories 4 and 5 (giving the most persistent type of

JSDC VOLUME 108 APRIL 1992 177

pollution) happens on most days of the week. Table 2 shows the type of pollution load associated with various coloration processes. Clearly all the various coloration processes on a number of substrates can have medium to high pollution potential.

Table 2 Type of pollution associated with various coloration processes

Fibre Dye class Type of pollution

Cotton Direct

Reactive

Vat

Sulphur

Wool Chrome

1 :2 Metal- complexes Acid

Polyester Disperse

1 Salt 3 Unfixed dyes (5-30%) 5 Copper salts

cationic fixing agents 1 Salt, alkali 3 Unfixed dyes (1 0-40%) 1 Alkali, oxidising agents 2 Reducing agents 1 Alkali, oxidising agents 2 Reducing agents 3 Unfixed dye (20-40%)

2 Organic acids 5 Heavy-metal salts 2 Organics acids

2 Organic acids 3 Unfixed dye (5-20%)

2 Reducing agents organic acids

5 Carriers

Thus the conclusion quite clearly is that textile wet processing does have the capability to pollute the en- vironment if not properly controlled. It is because the controls were not being applied (and consequently toxic, persistent and bioaccumulative chemicals are increasing in the aquatic environment) that the UK government introduced new controls in the Water Act of 1989.

THE WATER ACT This act privatised the ten regional water authorities in England and Wales, and this in itself will result in extra charges to industry. The water industry needs massive investment to improve the pipe and sewer system, some of which was laid in Victorian times, and to improve the treatment facilities. This investment is being recovered from the industrial user by an annual percentage figure of I + K , where I is annual inflation and K is an adjusting figure to recover investment costs. K can be positive or negative but has already been set for the next ten years at an approximate average 5% for years 1 to 5 and an average 3.9% for years 6 to 10.

Figure 2 shows the total effect to the year 2000 at an annual inflation rate of 7%. Prices can be expected to double, in real terms over that period if K remains static, but a ’pass through’ mechanism, which allows recovery of unforeseen costs, particularly environmentally impor- tant ones, can also be passed on to the consumer. Thus if

280

240

200

2 160

9 0 0

(c(

X

7

5 120 0

80

40

- A K = 15% B K = 10% C K = 5% years 1-5

= 3.9% years 6-10

J 90 92 94 96 98 2000

Figure 2 Effect of increasing Kfactors on costs

K averages 10% costs will quadruple over the period. This must be a concern and a threat to the textile wet process- ing sector as a large user of water in the UK

The opportunity, and it is a real opportunity in dyehouses that I visit, is to offset the threat with cost re- ductions. This can be achieved in a number of ways, some of which will require a little technical initiative, such as: (a) Reduction in water usage (b) Reuse of water (spent dyebaths, rinse baths, cooling

(c) Control of flows (d) Effluent management (e) Recovery of raw materials.

water)

Some options require capital outlay, others just re- quire sound common sense, but the pay-back can be well worth the effort. One of Courtaulds Textiles’ major dye- houses has achieved significant savings in a year by very specific and detailed water and effluent management (Figure 3).

60 t l

“E 50 5

.- g 55

6 45 0

40

z 35

30

25

r

v)

2 I I I I I I I I 1

5 10 15 20 25 30 35 40 45 50 Calender week

Figure 3 Savings achieved in 1990 in a Courtaulds dyehouse by specific and detailed water and effluent management

178 JSDC VOLUME 108 APKIL 1992

The Water Act also introduced three other key changes to water control legislation that will affect environmental control: (a) The formation of an independent regulatory body,

the National Rivers Authority (NRA), to take over the regulatory duties of the water authorities

(b) Formalised the principle of the 'polluter pays' (c) A statutory framework for both river quality stand-

ards and the control of drinking water, in my view linking the two irrevocably together.

The new regulatory body, the NRA, has already done more to enforce existing pollution controls, and as a result the20% of sewage treatment works that did exceed consent have improved. This has had an impact on industries in these particular areas and, though not yet widespread, reduced consent limits have had to be met with additional on-site facilities, with their attendant cost implications. However, real changes are becoming ap- parent, such as control of more specific compounds, reduction in the number and concentration of metals permitted, and the introduction of colour standards. These trends are of concern to the textile wet processing sector as the tighter controls on metals, such as copper and nickel, will affect dyestuff selection, and colour con- trols will fundamentally affect the use of reactive and acid dyes which are not adsorbed by sewage sludge and which pass through to the river. Additional treatments, either on site or at the municipal treatment works, to treat specialist effluents will cost more - under the 'polluter pays' principle - and this could represent an approx. 3-5% cost increase per metre of fabric.

This is only the start. The NRA recently published its longer-term view on how the control system can be improved, and some of the items relevant to the wet- processing sector are shown below: (a) Absolute limits on consents, including flow (absolute

compliance equals full, not proportional or percen- tile)

(b) Limits backed by percentile limits (c) Consistent application of limits for ammonia (d) Clearly defined toxicity limit for complex discharges

(e) TOWurbidity rather than COD/suspended solids (f) Limits on load (g) Action warnings prior to prosecution, based on both

(relevant to micropollutants)

types of effluent sample (composite and spot).

The introduction of these items, particularly absolute limits, ammonia consents, toxicity and limits on load can only increase the pressure on the wet processing sector. One positive point is that a change to total organic carbon (TOC) from chemical oxygen demand (COD) could help the sector as some of its COD load is inorganic!

As the regulator responsible for implementation of EC and North Sea Conference decisions, the NRA can also be expected to introduce further control parameters in the short term.

The Third North Sea Conference decisions require the reduction of certain specific substances discharged into river and the atmosphere, and hence the North Sea (including the Irish Sea), by 1995: (a) Reduction of 50% or more of 36 specified substances

by 1991 (now includes heavy metals and chloro- organics)

(b) Reduction of 70% or more of four specified substances by 1995 (major threat substances: dioxins, mercury, cadmium, lead)

(c) Substantial reduction of pesticides by December 1991 (d) Initiatives to reduce emissions of specified activities

(textile industry, persistent organic substances, AOX) (e) Initiatives to set priorities for control on a further 171

compounds.

Pesticide control affects wool and cotton processing (cur- rent pentachlorophenol issue), and AOX (adsorbable organohalogens) is already a major issue in Germany, and it can only be a matter of time before it assumes the same importance in the UK. The list of 36 substances requiring 50% reduction clearly influences dyehouse discharges, as a number of the metals (chromium, cop- per, nickel, zinc) are major constituents in some of the dyes and processing chemicals used. The opportunity here is to find alternative products. A case in point is the replacement of chromium dyes with metal-complex dyes. The cost advantage lies in the fact that the alternative will require less control measures, even if the alternative itself is a little more expensive. I am sure that suppliers can offer alternatives because a number of the multi-national companies are already selling more environmentally ac- ceptable products into parts of Western Europe where tighter environmental monitoring controls are currently in force.

The Third North Sea Conference also made a major strategic decision to avoid potentially damaging impacts even where there is no direct scientific evidence. I believe this represents a major change in thinking and will certainly appeal to the environmental lobby that 'dis- trusts scientists'. We must therefore adjust our thinking.

THE RED LIST Two recent pieces of UK legislation, namely the Trade Effluent (Prescribed Substances and Processes) Regula- tions, 1989, and the Environmental Protection Act, 1990, bring the so-called UK Red List substances under statu- tory control. The Red List is essentially a shortened version of List I (or the Black List) included in EC directive 76/464. While the approach to alternatives I have just described is also appropriate, this area of Red List control is made more difficult by lack of knowledge, lack of data and low levels of micropollutants in products. Perhaps the most quoted example is mercury in sodium hydrox- ide, but cadmium can be associated with zinc and deter- gents. After dilution, levels are often below 1 p.p.m., and even just a few p.p.b, but they have not been quantified because many processors are not aware that such

JSDC VOLUME^^^ APRIL 1992 179

micropollutants are present. However, the law does re- quire notification to Her Majesty’s Inspectorate of Pollu- tion (HMIP) if Red List chemicals are present. The industry must clearly liaise with the regulators (NRA and HMIP) to ensure that the controls required are achievable within the resources available and to establish the concept of BATNEEC (best available techniques not entailing exces- sive cost).

The relationship between the control of drinking wa- ter and the control of river quality, because of the abstrac- tion of drinking water, often downstream of treated effluent discharge, will also inevitably lead to more con- trols.

Table 3 shows a comparison of current textile effluent consent limits across the UK compared with the EC A31 maximum limits for drinking water. Generally dilution effects are sufficient to meet the required limits, but in some cases (e.g. copper, COD and grease/oil) further reduction in consent limits will require additional control to ensure the drinking water quality is maintained.

Table 3 Textile effluent consent limits across the UK compared with the EC A31 maximum limits for drinking water

Limits (p.p.m.)

EC A31 Average Maximum drinking industry industry water consent consent

Suspended solids 25 30 500 COD 30 800 1500 Oil 1 20 50 Mercury 0.001 Banned Banned Lead 0.05 1 .o 2.0 Chromium 0.05 1 .o 2.0 Copper 0.05 1 .o 5.0

These key changes again suggest cost implications but the opportunities identified previously are still relevant. Another opportunity is to look for alternative products, which could be more expensive, but which could give improved environmental performance while maintain- ing easy-care properties and thereby add value to the end product. A recent survey in the UK showed that the environment will be the most important consumer issue over the next decade and 36% of UK adults have values and attitudes consistent with ‘green’ consumerism.

ATMOSPHERIC POLLUTION The Environmental Protection Act, although not specifi- cally aimed at the textile wet processing area, does intro- duce controls that both directly and indirectly affect the wet processor. The act introduces major changes over the control of: (a) The discharge of Red List substances in textile efflu-

ents, controlled by HMIP (as covered above)

(b) Air emissions (c) Waste and waste disposal, including duty of care (d) Nuisance (noise, odour, smell).

Air emission control is to be split between two regula- tory authorities. Those processes that are the most pollut- ing (essentially those already covered by 1983 emission regulations) will be under HMIP control, while those processes that are less polluting but have an environ- mental impact (estimated at some 27 000operations across the UK), will be under local authority control. Most textile finishingprocesses will be in the second category and are covered in a section defined as ‘coating processes’. The definition of coating is not that traditionally used in the textiles sector but appears to cover surface application of any chemical to any substrate. The coating processes included, which must have the potential to emit volatile organic compounds (VOC) to atmosphere, cover use or application of polyurethane and polymer coatings, trans- fer coating processes and antisoiling, flame-retardant and waterproofing finishes, all of which are widely used in the textile industry via pad or bath application. Any VOC emission resulting from the use of solvent in any finish formulations, with solvent defined as a dissolver, a viscosity reducer or a cleaning substance (which there- fore includes wetting agents, surfactants, degreasers and cosolvents) will be encompassed by the control process.

Control will be exercised above a minimum consump- tion of five tonnes per year, even if solvents are only present as wetting agents in aqueous formulations. The substances and compounds covered are best described as ’those found in an organic chemistry textbook! and the list covers virtually all compounds that are likely to be emitted from textile finishing, coating and application processes: (a) Oxides of sulphur and other sulphur compounds (b) Oxides of nitrogen and other nitrogen compounds (c) Oxides of carbon (d) Organic compounds and hydrocarbons, including

(e) Heavy metals and their compounds (f) Smoke, grit, dust, fume (g) Asbestos (suspended particulate matter and fibres),

glass fibres and mineral fibres (h) Halogens and their compounds (i) Phosphorus and its compounds.

partial oxidation products

Table 4 shows the emission limits allowed, after appro- priate abatement (either recovery, incineration or ad- sorption); dilution and odour making are specifically forbidden.

These emission limits are currently the lowest in force in Western Europe, most even lower than TA Luft. All wet processors with coatingfinishing facilities and using pad techniques for finishes and for easy-care properties are faced with major changes and cost implications, the requirement being to use BATNEEC. The reference to excessive cost does not mean excessive to the business

180 JSDC VOLUME^^^ APRIL 1992

Table 4 Emission limits in textile, fabric coating and finishing processes

Emission limit (mg/rn3)(a)

Total VOC (as total carbon, excluding

Total particulate matter (including emissions particulate matter) 50

from material handling) 50 Carbon monoxide (from incinerators) 100 lsocyanates (as NCO group) 0.1 Formaldehyde 20

(a) Dilution and odour masking specifically forbidden

but excessive in terms of environmental control. The control, abatement and monitoring equipment required to meet the new limits is expensive, and a rule-of-thumb estimate is that the control equipment will double the price of the stenter on which it is installed.

Again there will be opportunities to offset the capital costs with process savings. With finishing processes this can be achieved by solvent recovery, heat recovery, and recirculation and reuse of acid vapours to neutralise alkaline liquors, a technique not currently favoured in the UK. A further option is the search for alternatives that add value and reduce environmental impact. This latter area is a major challenge, but the supplier industries and users must start discussing the implications now. Time is not on the side of industry. All coating process emission limits must be met by October 1997. However, by the end of 1992 all companies covered should have applied for authorisation to continue the process, and this request for authorisation should contain details of the control, abatement and monitoring equipment to be used, to- gether with an assessment of the results that will be achieved. By the end of 1992 therefore the industry has to know what can be achieved and how!

The Environmental Protection Act will also influence the way the industry manages waste and nuisance (noise, odour, smell). The introduction of a duty-of-care puts on the producer of waste the responsibility to ensure that the waste is disposed of in a responsible and effective manner. The system will therefore require more ad- ministration (checking of contracts, insurance, consign- ment notes, disposal routes), but some of the more intractable waste, e.g. heavy-duty plastic chemical con- tainers and chemical residues, will give additional prob- lems because of their toxicity or low biodegradability. The answer to the problem may be at the beginning of the cycle rather than end-of-pipe, and a dialogue on more environmentally acceptable packaging, including return- able, reusable options, will again need to be on the agenda. The suggested EC regulation on packaging (Figure 4), which requires a move from 20 to 60% of total packaging waste recycled, with a consequent reduction of packaging going to landfill from 60 to 10% within the next decade, can only hasten this requirement.

Prevention 10%

1990 2000

Figure 4 EC waste management targets for packaging (regulation rather than directive) (Source: ENDS report 190)

Tighter controls on nuisance, particularly boundary noise from machinery, and odour, fumes and/or smell from processing oils, residual monomers in formulations (e.g. acrylates) or polymerisation processes will require improved levels of containment. The control measure is to be 'the senses of the inspector', and therefore control- ling these items could be as costly as meeting an emission limit. Pay-back in this area of control is more difficult to quantify but an environmentally aware company with a respect for its neighbours and their quality of life is likely to enhance its reputation, certainly locally, and thereby attract good prospective employees. Waste production also implies waste minimisation possibilities. Thus re- duction of waste by improved efficiency, less packaging, recycling and reuse, must offer cost benefits.

CONCLUSION The growing level of pollutants in the environment will be controlled by increasingly tighter legislative control on discharges to water, air emissions, waste production and nuisance, and by much more active and powerful regulatory bodies. Failure to comply will result in heavier fines and more prosecution. The textile wet processing industry in the UK will certainly suffer under these new regimes if it does not control its processes effectively. A large number of these controls are completely new and are not related to poor performance against existing limits in the past. The cost threat, both capital and rev- enue, is quite significant. It has to be turned into both business and operational opportunities.

What does the textile industry in the UK have to do to achieve business sustainability? It needs to: (a) Make a commitment to the management of environ-

mental issues (discharges, emissions, waste, nuisance, energy) in its business strategy

(b) Audit and review performance on a regular basis (c) Formulate improvement plans, and build in cost re-

covery, including better water and effluent manage-

JSDC VOLUME^^^ APRIL 1992 181

ment, reuse and recycling of materials, less polluting alternatives with higher added value (d) Have a positive dialogue with suppliers, as the new

controls will most definitely affect the user-supplier interface

(e) Use environmental improvement as a I'R tool to en- sure the company image attracts good recruits, cus- tomers and consumers.

For industry to achieve those objectives, its managers need an individual commitment to conserve the environ- ment, to preserve what we have so that others may enjoy it. Perhaps, this is best summed up by some words attributed to the Haida people that I saw in a Sandoz environmental booklet:

The Air, the Water, the Soil are not a gift from our parents, but a loan from our children.

Decolorising textile effluents

Ingrid Steenken-Richter and W D Kermer BASF Aktiengesellschaft, Ludwigshafen, Germany

Amendments to the legislation on waste water are making the legal requirements for textile waste water more stringent. In addition to the limits on the metal content and the COD and AOX values, restrictions are also being placed on the colour of the effluent. Anionic dyes (e.g. reactive dyes and metal-complex acid dyes) are removed from spent dye liquors by means of ion pair extraction by long-chain amines. The effect of pH and the structure of the amine has been studied. In reactive dyeing such treatment reduces both the amount of colour and the AOX value. In the case of the metal-complex dyes the removal of the (chelated) metal is of prime importance. The metal-complex dyes can be recovered from the organic phase by extraction with caustic soda and then re-employed in dyeing. The amines that result at the end of dye recovery are practically colourless and may be reused.

INTRODUCTION The techniques adopted for the disposal of coloured effluents from textile dyeingand printing must be brought into line with the need to protect surface water and ground water. Some of the recent demands that have been imposed on textile effluents under German legisla- tion are shown in Table 1 [1,2].

Decolorising effluents has always been a major prob- lem, and reactive dyes present particular difficulties be- cause bath exhaustion is usually poor. After the dyeing process as much as 800 mgA of (hydrolysed) dye may

Table 1 Limiting permissible values for textile effluents (selected values) [1,2]

Discharged into Requirements for the treatment of

Water ways Drains branch streams

AOX (mg/l) 0.5 0.5 3 Cr (total) (mg/l) 0.5 0.5 2 Cu (mg/l) 0.5 0.5 2

Yellow (436 nm) 7 rn-l Red (525 nm) 5 m-' Blue (620 nrn) 3 m-l

(a) Spectral absorption coefficient

182 JSDC VOLUME^^^ APRIL 1992

remain in the bath. In addition, dyes are removed from the fibre, often in considerable amounts, during the subsequent rinsing and soaping. Although bath exhaus- tion of 1:l and 1:2 metal-complex dyes is much higher, the concentration of (chelated) heavy metals, especially in deep shades, may greatly exceed the above-men- tioned permissible limits in the effluent.

EXISTING METHODS Examples of methods that have been adopted up to now for decolorising effluents are presented in Table 2. They are often inadequate to achieve near total decolorisation as demanded in recent legislation. Some of them have been unable to gain a foothold for environmental reasons or because of excessive cost.

NEW METHOD A new method for decolorising effluents by ion pair extraction is described in Figure 1. In an acid medium, long-chain amines react with dyes containing sulphonate groups to form hydrophobic pairs of ions which accumu- late in the organic phase, e.g. the excess amine, and can thus be separated from the aqueous phase. The phase separation can be assisted by adding inert, non-polar solvents, preferably hydrocarbons. Examples of suitable amines include primary amines (aliphatic Ch-CI6 branched and unbranched, and aromatic such as