Textile industry threads its way through the effluent challenge

The textile industry was warned some time ago by the National Rivers Authority (NRA) that tighter controls on discharges of colour and pesticides were in the pipeline. Some sectors, such as the Kidderminster carpet manufacturers, have responded. But elsewhere the industry is warning - not for the first time - that thousands of jobs in textile finishing and garment manufacture are on the line because proven and economically feasible technology is not available to clean up its effluents.

Historically, effluents from the textile industry have had a major environmental impact on rivers in industrial areas. While the industry can boast some successes in tackling these problems, it now faces its toughest challenge yet as the NRA sets demanding standards for dyes and mothproofers to protect key rivers affected by textile effluents.

The NRA's approach has been to set target dates for compliance with the standards and warn both the textile industry and sewerage undertakers that these will mean strict new consents. This has caught the water companies between the textile industry on one side and the NRA on the other, with much to lose if the two positions cannot be reconciled.

Colour pollution
Colour is one of the most pressing problems facing the textile industry and has the highest public profile. A survey by the NRA last year found that colour affected 470 kilometres of river and provoked 557 complaints from the public.

The NRA commissioned a study on monitoring of colour in rivers and effluents from the University of Leeds two years ago. Now nearing completion, this will recommend a system of measuring light absorbance at several wavelengths which will form the backbone of a new national system for consenting colour in effluents.

In its Severn Trent region, which attracted the majority of public complaints about discoloured rivers in 1992, the NRA intends to impose new consent limits at the beginning of 1994. The timetable has caused most concern among the dyers and finishers in the East Midlands. About 60 companies concentrated around Nottingham, Leicester and Derby are represented by the Knitting Industries Federation (KIF). According to its Director, John Harrison, the NRA's consents are "not achievable with current end-of-pipe technology at a viable cost".

Problematic dyes
The KIF's member companies have spent about £300,000 investigating potential technologies, Mr Harrison says, and have concluded that none of the end-of-pipe solutions has been adequately tried and tested. The most problematical compounds are the reactive dyes, which provide the bright, fast colours now popular in cotton leisure wear.

The colour fastness of reactive dyes comes from their chemical reaction and fixation on the fibre. However, the same chemical reaction also occurs between the dye and the water in the dye-bath. Carefully controlled conditions minimise this side reaction but at best only 90% of the dye is fixed, leaving 10-50% of the dye in the effluent in a spent and inert form.

Spent reactive dyes are not removed by conventional sewage treatment processes. Additional techniques such as chemical flocculation, oxidation, ozonolysis, ultrafiltration or reverse osmosis are needed. But each of these has its difficulties, ranging from inadequate performance with some of the hundreds of reactive dyes available, to high capital cost or danger of creating toxic by-products.

Advances in dye technology offer no immediate prospect of a solution. Fixation of reactive dyes has already been greatly improved by the incorporation of several reactive sites on each dye molecule. According to John Easton of Zeneca Colours, one of the UK's major producers, further improvements would require a new type of reaction between the fibre and the dye. Developing and testing a new dye takes about five years, and Zeneca foresees no major improvement in the fixation of such dyes before the end of the decade.

End-of-pipe treatment
That solutions can be found is well illustrated by one company which is successfully treating its effluent for direct discharge into an East Midlands river. Stevensons Fashion Dyers, part of the Coats Viyella group, has recently extended its effluent treatment plant to cope with expanding production. The firm's factory at Ambergate, Derbyshire, dyes and finishes 180 tons of knitted goods on a commission basis each week - and produces 10 million gallons of effluent in the process.

At today's prices the company estimates that its effluent treatment plant represents an investment of £3 million. In response to changes and expansion in output since the 1960s, the plant has been developed from a filtration and activated sludge system and now includes two new dissolved air flotation systems designed to remove waste colour.

The system is particularly effective at removing reactive dyes. The effluent is dosed with cationic polymers which precipitate surplus dye from the effluent. The dye particles are flocculated and collected by small bubbles of air. The solids form a scum which is readily separated from the effluent surface. Sludge from the process is passed through a filter press before landfilling, while the effluent is passed through a heat exchanger before discharge into the river Amber.

However, the KIF points out that Stevensons has advantages which many of its members lack. Many companies in the East Midlands are located in cities, surrounded by other developments, and do not have room for effluent treatment plant. They are not located close to rivers and must therefore discharge to sewer. The addition of coagulants for colour treatment is further constrained by their compatibility with sewage treatment systems, according to the KIF.

The perceived advantages of discharging directly to a river may in any event be short-lived as the NRA continues to press for improvements in river quality. However, successful removal of colour by end-of-pipe technologies does involve investment of £3-5 million in treatment plant and up to an acre of land.

The KIF argues that there is no easy solution for many of its members and that the colour problem is purely aesthetic. Modern dyes have low toxicity and the NRA concedes that there is no evidence of direct toxic effects. However, it is responding to public perceptions that colour is a highly visible form of pollution, as well as anecdotal evidence that colour may affect fish, plant and invertebrates in rivers.

Role for sewerage undertakers
The ultimate solution, the KIF claims, is for colour to be removed at sewage treatment works - but the suggestion is not one that has been welcomed by the water companies. In the few cases where it has been attempted, colour removal at sewage works has proved expensive and difficult.

Severn Trent Water has invested heavily in colour removal at its Leek sewage works in Staffordshire. The plant treats effluent from local dyers which comprises 60% of its total load. Severn Trent decided to replace the works' ageing and ineffective alum coagulation plant with an ozonation unit costing £2.2 million. Additional balancing tanks, pumps and sand filters brought the total outlay up to £5.1 million.

In 1991, teething troubles with the new plant cost the company eleven convictions for pollution offences and fines totalling £22,000 as it repeatedly failed to meet its consent (ENDS Report 200, p 36). Since fractures in the plant's ozone contactor pipes were repaired in October 1992, the works has had a much improved record. However, it still failed four out of 38 routine NRA tests, although there have been no recent colour complaints downstream on the river Churnett.

Severn Trent Water intends to recover the cost of the plant from dischargers. Final effluent charges are about to be fixed, but initial calculations suggested that textile companies face a doubling of their effluent charges.

Severn Trent insists that Leek is a special case and has no plans to introduce ozonation at any of its other works treating coloured effluents, such as Wanlip, Pinxton, Wigston and Loughborough. Textile effluents form a much smaller proportion of the total load to these plants, making the costs of ozonation prohibitive, the company says.

At Wanlip, Severn Trent is conducting trials with a poly-electrolyte coagulation system. This is successfully reducing colour, but not consistently to levels that enable compliance with new NRA consents. The company describes the capital costs of these systems as "moderate", and the technology appears to hold out good potential for development through selection of coagulants and pH controls.

Salutary prosecution
The NRA's intention to introduce new colour consents early in 1994 has prompted the KIF and Severn Trent Water to co-operate in devising a solution. At a meeting in October, the industries proposed an action plan which would allow more time to achieve compliance. However, in exchange for a possible extension of the deadline, the NRA is seeking firm targets for colour reductions.

The NRA's sanction would be to tighten consents for sewage discharges, forcing the water company to reduce the levels of colour permitted in its trade effluent agreements with dischargers so that it stayed within the law itself. The textile companies could appeal against these restrictions, in which case Severn Trent would have little defence against prosecution by the NRA unless it lodged an appeal itself.

North West Water found itself in precisely this situation after discharges of the "red list" substance pentachlorophenol (PCP) to its Belmont sewage works by a textile finishing business caused a breach of the environmental quality standard for PCP in a brook (ENDS Report 205, p 39 ). The company, Belmont Bleaching & Dyeing, appealed to the Secretary of State against North West Water's attempt to tighten its consent for PCP.

North West Water was found guilty and fined, despite the pending appeal, as the NRA alleged that it could have taken additional measures to reduce PCP levels in its own discharge. The lesson was a salutary one for the water industry, which now recognises the costs of being sandwiched between dischargers and the NRA in disputes over discharges.

Both the textile industry and water companies have much to lose from a failure to meet the NRA's tighter standards. However, the KIF can regard its members in the Severn Trent area as fortunate. Those in Yorkshire appear to be in for a much tougher time.

Yorkshire Water's hard line
In Yorkshire, the NRA is tackling colour as just one of the many problems affecting several badly polluted rivers. It is tightening consents and envisages a major improvement in river quality by 1997 as sewage works are refurbished. Yorkshire Water has already appealed against some of the NRA's revised consents for sewage discharges which it is unable to meet because of textile trade discharges.

However, the company is itself signalling that it will be taking a tougher line on trade effluents in the future. The policy was outlined by Tony Shuttleworth, its Director of Water Quality, at an Institute of Water and Environmental Management conference on textile industry effluents in September. The paper caused a good deal of surprise and some disbelief.

Yorkshire Water is allowing no additional capacity for treating trade discharges in the redesign of its new sewage works, Dr Shuttleworth revealed. The company is aiming to minimise capital and operating costs because of a shortage of funds and because revenues from trade effluents are "insufficient" to justify the risk of investment in new capacity. A further factor is the 1991 EC Directive on wastewater treatment, which sets challenging limits on COD discharges from sewage works.

Yorkshire Water has just completed a review of all 2,500 of its trade effluent agreements, removing excess capacity and introducing load limits on larger discharges. In the longer term, it expects to constrain industrial discharges and drive down levels of contaminants and intractable substances like colour. And it is aiming to achieve effluent strengths similar to that of domestic sewage on all trade discharges by the end of the 1990s.

Dr Shuttleworth warned that this will "require a great deal of attention" from the textile and other sectors which commonly produce effluents with COD values in excess of 10,000mg/l. The company anticipates allowing maximum COD values an order of magnitude below this.

Clean-up successes
Despite the current bleak outlook, the textile industry can look to several recent successes on the environmental front. Many of the Yorkshire rivers which accept wool scouring effluents were badly polluted with organochlorine pesticides such as DDT, lindane and dieldrin in the mid-1980s. The compounds were present in fleeces as a result of sheep dipping practices in the UK and overseas, and were also used as mothproofers.

However, following the replacement of organochlorines and the introduction of strict quality assurance programmes in many wool producing countries, organochlorine levels declined rapidly. Current levels are well within EQSs.

Toxic mothproofers
Treatment of fibres with mothproofers, chiefly for carpet making, has for many decades been another source of pesticide pollution. Organochlorines such as dieldrin were replaced some time ago with less persistent synthetic pyrethroids such as permethrin and cyfluthrin. However, this has not meant an end to the impact of mothproofers on rivers.

In 1990, levels of permethrin in the Stour below Kidderminster sewage works averaged 75ng/l, well above the EQS of 10ng/l (ENDS Report 185, p 7). The sewage works treats discharges from six carpet manufacturers in the area.

The problem was recognised in 1988 by the then Severn Trent Water Authority, which attempted to relax the consent for the sewage works and tighten trade effluent agreements. But the carpet manufacturers appealed against the revised consent limits and the Department of the Environment refused to allow a relaxation of the sewage works' consent.

Carpet industry's action plan
The deadlock was broken after the newly formed NRA forged an agreement with the carpet manufacturers and the water company. The action plan set a deadline of the end of 1995 to bring permethrin levels in the river below the EQS.

Impressive progress has since been made in reducing permethrin discharges. The sewage works is now discharging the pesticide at levels which allow the EQS to be met most of the time. The carpet producers have withdrawn their appeals and are accepting more stringent discharge limits.

There has been a marked improvement in the biology of the Stour and below its confluence with the Severn. Although a good Class 1b river at this point, the Severn had a biological quality score of only 40 in 1989, which was much less than expected. Now the score is about 95, and the biological quality is similar above and below the confluence with the Stour.

The carpet manufacturers achieved the reduction in permethrin loads by a co-operative effort which involved the exchange of commercial information between competitors. Progress so far has been achieved by a combination of improved house-keeping, limiting applications to the minimum effective levels, substitution of permethrin with other pyrethroid mothproofers, and balancing the load on the sewage works.

Controls over the mothproofing process have been tightened, reducing permethrin discharges and achieving greater consistency of treatment, according to Eric Cooper of Carpets of Worth and spokesman for the Kidderminster and District Carpet Manufacturers and Spinners Association. By careful timing and measurement, maximum exhaustion of the chemical onto the wool is achieved. All spillages and washings of mothproofers are returned to the dyebath to minimise losses.

The companies spent some £30,000 on consultancy fees and better measuring and monitoring equipment. However, one benefit has been a reduction in the cost of the active ingredient of about 50-60%. All the companies currently keep 24-hour composite effluent samples for inspection by the water company, and these allow close scrutiny of permethrin discharges to and from the sewage works.

Dispute over product quality
One controversial method by which permethrin discharges have been reduced is by cutting the level of mothproofer in the finished wool. The companies believe that adequate moth protection can be achieved by applications at less than half the level recommended by the International Wool Secretariat (IWS). They have removed safety factors designed to accommodate pesticide losses during wear and tear and to protect against inaccuracies during application.

The policy has opened a major rift in the industry. The IWS, which represents the interests of major wool producing countries such as Australia, New Zealand, South Africa and Uruguay, believes that the Kidderminster companies risk compromising not only the quality of their own products but also the reputation of wool carpets in general. At the same time, it is following a different road toward achieving the higher environmental standards required by the NRA.

IWS is developing new mothproofing technologies to suit the major companies processing overseas carpet wools, mainly concentrated in Yorkshire. One of these, the Enviro-Proof minibowl, is now available commercially and is being used by companies in Dewsbury. It consists of a final treatment vessel at the end of a scouring yarn production line, containing a small volume of mothproofing liquor. The liquor can be cleaned and recirculated to minimise the loss of mothproofer.

According to the IWS, the Enviro-Proof system results in permethrin releases of only 0.015g per tonne of wool, compared with 50-100g/t with traditional methods. The capital cost is £50,000-£300,000, but the IWS claims a pay-back within two years due to savings on mothproofers and other chemicals.

A second system currently at the pilot stage is suitable for treating batches of scoured and dyed wools. Batches of wool are treated with hot mothproofer emulsions in a centrifuge. This should be capable of achieving permethrin emissions of 1.6-8.0g/tonne, depending upon the batch size.

These systems will enable the Yorkshire industry to comply with stiff new trade effluent consents which will be imposed next year, the IWS believes. In contrast to the Stour, permethrin concentrations in some Yorkshire rivers are still well above the EQS. For example, after inputs from the Huddersfield and Brighouse sewage works, permethrin levels in the river Calder reach 590ng/l, nearly 60 times the EQS (see figure ).

The NRA has set a deadline for compliance with the EQS in Yorkshire by the end of 1994, which will force Yorkshire Water to rein in permethrin discharges to its sewers. As yet, the NRA says it has seen little evidence that the textile industry is rising to the challenge.

As Yorkshire Water proceeds with its programme of rebuilding major sewage works, the NRA is expecting to see marked improvements in rivers such as the Aire and Calder. These are the main receptors of textile effluents in the region and among the most polluted watercourses in the country. Mothproofers jeopardise this improvement, and the NRA is unlikely to listen sympathetically to last-minute pleas from the industry that there has been insufficient warning of changing standards.

Sheep dip pesticides
Though solutions to mothproofer discharges are now available, the industry has had little breathing space to confront yet another problem. Just as the replacement of dieldrin as a mothproofer led to discharges of synthetic pyrethroids, the replacement of organochlorine sheep dips has produced organophosphate discharges in wool processing effluents.

In the river Stour, the NRA began to detect diazinon and propetamphos downstream of Kidderminster sewage works in 1990. The compounds are widely used as active ingredients of sheep dips in the UK and overseas. They are highly toxic to aquatic life, and annual average EQSs of 10ng/l have been proposed for each compound, with a maximum peak concentration of 100ng/l (ENDS Report 218, pp 8-9 ).

Both these values are exceeded in the Stour, according to NRA monitoring. Average concentrations are 40ng/l and 30ng/l, and peak concentrations are 220ng/l and 310ng/l, for diazinon and propetamphos respectively.

The NRA concedes that organophosphates in wool effluents are likely to remain a problem for a considerable time. Even the extent of the problem is not yet fully appreciated. In Yorkshire, where wool scouring is likely to release large quantities of organophosphates, the compounds are difficult to detect in rivers because of the presence of many other pollutants.

There is no readily available technical means of removing low levels of organophosphates in effluents, and the textile industry is focussing its efforts on controlling organophosphate levels in fleeces. According to the IWS, overseas wool producers are well advanced in this area. Producers in New Zealand and Australia, for example, are discussing best practice methods to minimise residues and quality assurance and monitoring schemes. However, there has been no sign from the Ministry of Agriculture or the British Wool Marketing Board that similar measures are being considered in the UK.

For UK farmers, wool is a secondary product and there are many small producers. Policing a quality assurance system under these circumstances would be difficult because the cost of analysis might well exceed the value of the wool. Many farmers would also be unlikely to take great care over a low-value product. However, a further issue with the organo-phosphates is that the Government is under strong pressure to ban the compounds on health and safety grounds.

The NRA has told the Ministry of Agriculture that it does not favour a wholesale replacement of sheep dip chemicals unless the environmental effects of alternatives are well understood. However, there are few completely effective alternatives, except synthetic pyrethroid dips, which may exacerbate an existing problem for the wool industry.

The Ministry appears unlikely to ban organophosphates until there are advances in pour-on or other technologies which offer both safety and environmental advantages. The textile industry will be hoping that solutions emerge quickly before it is forced into further research, development and investment to tackle yet another effluent problem.

Please sign in or register to continue.

Sign in to continue reading

Having trouble signing in?

Contact Customer Support at
or call 020 8267 8120

Subscribe for full access

or Register for limited access

Already subscribe but don't have a password?
Activate your web account here