Multilateral Investment Guarantee Agency

Environmental Guidelines for Dye Manufacturing

Industry Description and Practices dyes by use classification comprises the following: This document addresses the synthesis of dyes • Acetate rayon dyes: developed for cellulose acetate and pigments used in textiles and other and some synthetic fibers; industries. Dyes are soluble at some stage of the • Acid dyes: used for coloring animal fibers via application process, whereas pigments in acidified solution (containing sulfuric acid, acetic acid, general retain essentially their particulate or sodium sulfate, and surfactants) in combination with crystalline form during application. A dye is amphoteric protein. used to impart color to materials of which it • Azoic dyes: contain azo group (and formic acid, becomes an integral part. Aromatic ring caustic soda, metallic compounds, and sodium nitrate) structure coupled with a side chain is usually especially for applying on cotton . required for resonance and in turn impart color. • Basic dyes: amino derivatives (and acetic acid and Resonance structures which cause displacement softening agents) used mainly for application on paper. or appearance of absorption bands in the visible • Direct dyes: azo dyes (and sodium salts, fixing spectrum of light are responsible for color. agents, and metallic [chrome and copper] compounds) used Correlation of chemical structure with color has generally on cotton-wool or cotton-silk combinations. been accomplished in the synthesis of dye using • Mordant or chrome dyes: metallic salt or lake formed a chromogen-chromophore with auxochrome. directly on the fiber by the use of aluminum, chromium, or Chromogen is the aromatic structure containing iron salts which cause precipitation in situ. benzene, naphthalene, or anthracene rings. A • Lake or pigment dyes: form insoluble compounds chromophore group is a color giver and is with aluminum, barium, chromium, on molybdenum [Mo] represented by the following radicals which salts, the precipitates are ground to form pigments used in form a basis for chemical classification of dyes paint and inks. when coupled with the chromogen: (a) azo (- • Sulfur or sulfide dyes: contain sulfur or precipitated N=N-); (b) carbonyl (=C=O); (c) carbon from sodium sulfide bath; furnish dull shades with good (=C=C=); (d) carbon-nitrogen (>C=NH or - fastness to light, washing, and acids, but susceptible to CH=N-); (e) nitroso (-NO or N-OH); (f) nitro chlorine and light. (-NO2 or =NO-OH); (g) and sulfur (>C=S, and • Vat dyes: impregnated into fiber under reducing other carbon-sulfur groups). The conditions which reoxidizes to an insoluble color. chromogen:chromophore structure is often not Chemical classification is based on sufficient to impart solubility and to cause chromogen. For example, nitro dyes have the adherence of dye to fiber. The auxochrome or chromophore - NO2 under which Naphthol bonding affinity groups are amine; hydroxyl; Yellow S, C.I. 10 is classified. The coding S carboxyl; and sulfonic radicals or their comes from commercial designation and relates derivatives. These auxochromes are important to color or application (B - for bluish; G - for in the use classification of dyes. A listing of greenish or yellowish [gelbich in German]; R - reddish; S - sulfur containing or dye for silk; W -

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wool dye; L - lake forming, easily soluble of COD, 6 kg of suspended solids, and 30 g of [loslich in German ], or for linen). The Color oil and grease per kg of product. Index (C.I.) published by the Society of Dyers Major solid wastes of concern include and Colourists (UK), in cooperation with the filtration sludges, process and effluent American Association of Textile Chemists and treatment sludges, and container residues. Colorists (AATC), provides a detailed Examples of wastes considered toxic include classification of commercial dyes and pigments wastewater treatment sludges, spent acids, and by generic name and chemical constitution. This process residues from the manufacture of sourcebook also provides useful information on chrome yellow and orange pigments, technical performance, physical properties, and molybdate orange pigments, zinc yellow application areas. pigments, chrome and chrome oxide green Dyes are synthesized in a reactor, filtered, pigments, iron blue pigments, and azo dyes. dried, and blended with other additives to produce the final product. The synthesis step Pollution Prevention and Control involves reactions such as sulfonation, halogenation, amination, diazotization, and Every effort should be made to substitute highly coupling followed by separation processes toxic and persistent ingredients with degradable which may include distillation, precipitation, and less toxic ones. Recommended pollution and crystallization. In general, organic prevention measures are: compounds such as naphthalene are reacted • Avoid the manufacture of toxic azo dyes and provide with an acid or an alkali along with an alternative dyestuff to users such as textile manufacturers. intermediate (such as a nitrating or a • Meter and control the quantities of toxic ingredients sulfonating compound) and a solvent to form a to minimize wastage. dye mixture. The dye is then separated from the • Reuse by-products from the process as raw materials mixture and purified. On completion of the or as raw material substitutes in other processes. manufacture of actual color, finishing • Use automated filling to minimize spillage. operations including drying, grinding, and • Use equipment washdown waters as make-up standardization are performed and these are solutions for subsequent batches. important for maintaining consistent product • Return toxic materials packaging to supplier for quality. reuse, where feasible. • Find productive uses for off-specification products to Waste Characteristics avoid disposal problems. • Use high pressure hoses for equipment cleaning to The principal air pollutants are volatile organic reduce wastewater generated. compounds (VOCs), nitrogen oxides (NOx), • Label and store toxic and hazardous materials in hydrogen chloride (HCl), and sulfur oxides secure bunded areas. (SOx). A dye and pigment manufacturing plant Liquid effluents resulting from equipment should prepare and implement an Emergency cleaning after batch operation, can contain toxic Plan which takes into account neighboring land organic residues. Cooling waters are normally uses and the potential consequences of an recirculated. Wastewater generation rates are of emergency. Measures to avoid the release of the order of 1-700 liters per kg (L/kg) of harmful substances should be incorporated in product except for vat dyes. The wastewater the design operation, maintenance, and generation rate for vat dyes can be of the order management of the plant. of 8,000 (L/kg) of product. The biochemical oxygen demand (BOD5) and chemical oxygen Target Pollution Loads demand (COD) levels of reactive and azo dyes can be of the order of 25 kg and 80 kg per kg of Implementation of cleaner production processes product respectively. Values for other dyes are, and pollution prevention measures can provide for example, 6 kg of BOD5 together with 25 kg both economic and environmental benefits.

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Specific reduction targets for the different The following guidelines present emission processes have not been determined. In the levels normally acceptable to the World Bank absence of specific pollution reduction targets, Group in making decisions regarding provision new plants should always achieve better than of World Bank Group assistance, including the industry averages quoted in the section on MIGA guarantees; any deviations from these Waste Characteristics. levels must be described in the project documentation. Treatment Technologies The guidelines are expressed as concentrations to facilitate monitoring. Dilution Air Emissions of air emissions or effluents to achieve these guidelines is unacceptable. Stack gas scrubbing and/or carbon adsorption All of the maximum levels should be (for toxic organics) are applicable and effective achieved for at least 95% of the time that the technologies for minimizing the release of plant or unit is operating, to be calculated as a significant pollutants to air. Combustion is used proportion of annual operating hours. for the destruction of toxic organics. Combustion devices should be operated at Air Emissions temperatures above 1,1000C (when required for the effective destruction of toxic organics) with The following emissions levels should be a residence time of at least 0.5 second. achieved:

Liquid Effluents Emissions from Dye Manufacturing Parameter Maximum value Effluent treatment normally includes (milligrams per neutralization, flocculation, coagulation, normal cubic meter settling, carbon adsorption, detoxification of (mg/Nm3)) organics by oxidation (using ultraviolet systems or peroxide solutions), and biological treatment. Chlorine (or chloride) 10 Exhausted carbon from absorption processes VOCs 20 may be sent for regeneration or combustion. Reverse osmosis, ultra-filtration and other Liquid Effluents filtration techniques are used to recover and concentrate process intermediates. The following effluent levels should be achieved: Solid Hazardous Wastes Effluents from Dye Manufacturing Contaminated solid wastes are generally Parameter Maximum value incinerated and the flue gases, when acidic, are milligrams per scrubbed. liter (mg/L) Emission Guidelines PH 6-9 BOD5 30 Emission levels for the design and operation of COD 150 each project must be established through the Total suspended solids 50 Environmental Assessment (EA) process, based Oil and grease 10 on country legislation and the Pollution Prevention and Abatement Handbook as applied to Phenol 0.5 local conditions. The emission levels selected Chromium (hexavalent) 0.1 must be justified in the EA and acceptable to Copper 0.5 MIGA. Zinc 2 AOX 1

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Toxic organics such as 0.05 every shift. The remaining parameters should benzidine (each) be monitored at least on daily basis. Monitoring data should be analyzed and

reviewed at regular intervals and compared Note: Effluent requirements are for direct with the operating standards so that any discharge to surface waters. necessary corrective actions can be taken. Solid Wastes Records of monitoring results should be kept in an acceptable format. These should be reported to the responsible authorities and relevant Contaminated solid wastes should be parties, as required, and provided to MIGA if incinerated under controlled conditions to requested. reduce toxic organics to non-detect levels (in no case to exceed 0.05 mg/kg or health-based level). Key Issues

Ambient Noise The following box summarizes the key production and control practices that will lead to compliance Noise abatement measures should achieve with emission guidelines: either the following levels or a maximum • increase in background levels of 3 dB(A). Avoid the manufacture of toxic azo dyes and provide Measurements are to be taken at noise receptors alternative dyestuff to users such as textile located outside the project property boundary. manufacturers. • Substitute highly toxic and persistent ingredients with less toxic and degradable ones. • Control loss and wastage of toxic ingredients. Ambient Noise • Return packaging for refilling.

Maximum Allowable Leq • Use equipment washdown waters as make-up solutions (hourly), in dB(A) for subsequent batches. Receptor Daytime Nighttime • Minimize wastage by inventory control and find uses 07:00 - 22:00 22:00 - 07:00 for off-specification products.

Residential; 55 45 Further Information institutional; The following is suggested as a source of educational additional information (this sources provided Industrial; 70 70 for guidance and not intended to be commercial comprehensive): Kirk-Othmer. 1980. Encyclopedia of Chemical Technology. Third Edition. New York: John Wiley and Sons. The emission requirements given here can be Austen, G. Shreve’s Chemical Process consistently achieved by well-designed, well- Industries, McGraw-Hill Book Co., Inc., New operated and well-maintained pollution control York. systems.

Monitoring and Reporting

Frequent sampling may be required during start-up and upset conditions. Once a record of consistent performance has been established, sampling for the parameters listed above should be as detailed below. Monitoring of air emissions should be on a continuous basis. Liquid effluents should be monitored for toxic ingredients at least once