Contents
Contributors vi
Introduction by Peter Cooper 1
PART ONE The problem of colour
1 The dye maker’s view by John R Easton 9
2 The regulator’s view by Brian D Waters 22
3 The water company’s view by John H Churchley 31
4 The trade association’s view by John Harrison 44
PART TWO The search for solutions
5 Industry evaluation of colour reduction and removal – the DEMOS project
by Barry G Hazel 59
6 Technical solutions to the colour problem: a critical review by Timothy G Southern 73
7 The treatment of dyehouse effluent at Stevensons Fashion Dyers by John Scotney 92
8 The treatment of dyehouse effluent at John Heathcoat by Eric J Newton 101
PART THREE Currently available technologies
9 Macrosorb colour treatment systems by Keith R F Cockett and Maurice Webb 113
10 Arcasorb D dye effluent treatment process by Philip C Blowes, Anne Jacques and David Jones 128
11 Treatment of dyehouse effluent for subsequent re-use of reclaimed water
by Peter H Weston 143
12 Membrane technology for the separation of dyehouse effluent
by Clifford Crossley 155
13 Colour removal from dyehouse effluents using synthetic organic coagulants
by Peter J Hoyle 171
14 Effluent treatment using chemical flocculation by Brian W Iddles 185
PART FOUR Novel technologies
15 Dyeing in nonaqueous systems by David M Lewis 195
Introduction
Peter Cooper
The environmental issues associated with residual colour in treated textile effluents are not new. Indeed, for the last decade or so a number of direct dischargers, both sewage treatment works and commercial textile operations, have had to perform to colour requirements placed on the treated textile effluent discharge, which have been progressively and perceptively tightened. What is perhaps new in the past three to four years in the UK is the higher focus placed by the regulator on public complaints about coloured watercourses and the consequent debate about how control should be exercised to improve the situation and reduce the colour problem to an acceptable level. This debate has widened the traditional discussion/ negotiation base from regulator and discharger to regulator, sewerage undertaker and sewer discharger; moreover, because of technical and operational concerns the debate base has widened further to include the dye supplier, trade associations, control equipment suppliers and government departments.
The technical and operational concerns which have widened the debate have included:
– improving the fixation of certain dyes on specific substrates
– chemical structure change of certain dyes to give more biodegradable/bioaccumulated alternatives
– identifying the most cost-effective point in the discharge chain to remove pollution
– the availability of large-scale colour removal processes
– the effectiveness of technical removal techniques to remove various admixtures of dyes
– the ‘best practicable environmental option’ (BPEO) argument, which suggests that some techniques produce more significant environmental impact (sludge production, landfill options, toxic breakdown products) than that of colour alone
– cost benefits that colour and pollutant removal achieve, particularly with water recycle
– the space implications of new installations, and hence the asset implications of end-ofpipe treatment for some businesses in restricted locations
– the sector infrastructure impact, particularly on small independent businesses, of significant control investment.
The list is by no means exhaustive. It does, however, indicate why there are so many ‘players’ in the debate and in the search for effective, viable treatments at sewage treatment works or on site, and why the textile operator may feel that there is a need for a clearer picture of the facts of the matter and what the options are for the future.
This publication seeks to put the positions of all the players into perspective and to clarify the current position. It aims to help the textile operator to decide on options available to plan forward strategy that will ensure compliance with the regulators’ requirements on a progressive basis. To achieve this objective this publication is divided into parts, each of which consists of chapters in which all the various views, opinions, positions and solutions are explained and developed. It should be remembered that this can only represent a snapshot of a rapidly changing scene in terms of regulations, control technology and cost.
The first chapter in Part 1 presents the dye maker’s view, on behalf of the Chemical Industries Association; it discusses the main causes of the problem by class, substantivity and fixation, the biodegradation and/or bioaccumulation and general behaviour of the various dye classes in effluent treatment and structure modification possibilities to cure the problem. In the second chapter the regulator, the National Rivers Authority (NRA), identifies the need for the control of colour and covers the perceived effect of colour on ecosystems. The colour-measurement techniques employed to quantify the problem and the translation of this into limits are also covered.
The most modern colour removal technology installed at a sewage treatment works in the Severn Trent Water operation in central England is reviewed in Chapter 3. The controls introduced, the effectiveness of the system and the implications of this experience on research and development to control the problem at sewage treatment works are discussed. Chapter 4 concentrates on the industry view, detailing the ‘political’ attempt, by the association concerned about the gap between regulatory requirement and technical feasibility, to ensure the industry had a sensible timescale in which to act.