The discoloration of rivers by effluents from the dyeing industry is at its most acute in the Severn Trent region. The NRA says that the problem has worsened as the industry has switched to reactive dyes. These give improved colour-fastness, but are poorly biodegradable in sewage treatment works. Ten rivers in the region are affected by colour pollution, compared to two or three a few years ago.
Other rivers affected by textile dyes include the Goyt in north Derbyshire and the Irwell near Rossendale, both in the NRA's North West region, as well as some stretches of water in Yorkshire and Scotland.
Most of the industry discharges its effluents to sewer and, in the face of growing complaints from anglers about colour pollution, the NRA has begun addressing the issue by leaning on the water companies to improve their trade effluent control practices. But a warning of things to come has been sounded by its Severn Trent region, which recently told Severn Trent Water that it has two years to eliminate the colour problem caused by discharges from its sewage works at Leicester and Loughborough - both major centres of the dyeing industry.
Severn Trent Water has already been forced to make major investments at its sewage works in Leek, Staffordshire, following an NRA prosecution over excessive discharges of colour (ENDS Report 200, p 36). The works has been equipped with tertiary filters and an ozonation plant at a cost of several million pounds to break down textile dyes.
A similar solution is unlikely at other locations. More than 30% of the inflow to the Leek works comprises dyehouse effluent. The figure is much smaller at other major dyeing centres, and installing special treatment facilities would not be cost-effective.
The sector most affected by the NRA's tougher line is represented by the Knitting Industries' Federation (KIF), which has 26 commission dyers and finishers and more than 30 vertically integrated textile businesses in membership. According to a spokesman, 75-80% of these firms operate in areas where colour pollution is causing concern.
The KIF says its members are having to address the problem in a "technology void." The option of installing something akin to a sewage works would be prohibitively expensive, and many dyeing businesses operate in city centres where space is at a premium. Studies under way at March Consulting and the British Textile Technology Group are attempting to identify cheaper options, but the KIF says that at least four years will be needed to bring these to commercial fruition.
The NRA's Severn Trent region is working to a tighter timetable. "We have no choice - we cannot tolerate brightly coloured rivers," a spokesman insisted. "We will give the industry a reasonable period of time, but we expect improvement." Companies in the region will have two years to find a solution, or perhaps a few months longer if they can show that they have an improvement programme in hand. The NRA has also warned that it will respond to any new colour pollution by imposing a "no artificial colour" condition on the offending discharge.
Experience suggests that the problem can be reduced significantly by good housekeeping measures at dye-houses. Tighter trade effluent control by North West Water has cut down dye spillages at works on the Irwell.
A long-term solution will require improved segregation of dyehouse effluents, with the small volumes of strongly coloured liquids being kept separate from other waste streams. This will help to reduce dyeing companies' costs by facilitating water recycling, while the problematic effluent will be more amenable to treatment, either on site or after tankering away.
The Textile Finishers' Association, which says that most of its 50 member companies have colour problems, is also looking into the possibility of adding a precipitant to the effluent so as to promote settlement of dyes at the receiving sewage works.