The dyestuff sector is one of the important segments of the chemicals industry in India, linked with a variety of sectors like textiles, leather, paper, plastics, printing inks and foodstuffs. Unit operations and process involved in manufacturing of dyes and dye intermediates, wastewater characteristics of dyes and dye intermediates, effluent discharge standards, treatment technology for dye and dye intermediates, solid waste generation and Gaseous emissions.

1. Dye and Dye Intermediate
Industries
Presented by
Deepak Waghmare
Environment Engineer
Vapi Green Enviro Ltd

2. Contents
• Introduction
• Raw Materials
• Unit Processes and Operations
• Classification of Dyes
• Application in Textile Industry.
• Waste generation
• Sources of wastewater
• Characteristics of Dye wastewater
• Effluent discharge standards
• Dye wastewater treatment
• Solid Waste
• Gaseous Emission

3. Dyes and Dye Intermediates
• The dyestuff sector is one of the important segments of the chemicals
industry in India, linked with a variety of sectors like textiles, leather,
paper, plastics, printing inks and foodstuffs.
• Dyestuff is a general industry term covering both dyes and pigments in
terms of chemistry, reactions and properties.
• Dyes are any substance, natural or synthetic, used to color various
materials, and have wide industry applications ranging textiles, leather,
food, and paper etc.
• Dyes are designed to resist natural elements such as sunlight, wind
and man-made elements like oxides of nitrogen, hydrolysis etc.
• There are about 600 types of dyestuffs produced in the country.

5. Raw Materials
• Raw materials used in the manufacture of dyes are mainly
aromatic hydrocarbons, such as benzene, toulene, naphthalene,
anthracine, pyrene, phenol, pyridine etc.
• Dye intermediates are the main raw material used for the
manufacturing dyestuff.
 Naphtha and natural gas are used for the production of
benzene and toluene, which are subsequently used for
manufacturing nitro-aromatics.
 The nitro-aromatics are then used for manufacturing the
compounds called dye intermediates.
 Examples of major dye intermediates are Vinyl Sulfate.

6. Indicative Operation Sequence
for Dye Manufacture

7. Unit Processes and Operations
• A unit process may be defined as a production stage that
involves chemical reactions.
• Typically, dyes and dye intermediate are synthesized in a
reactor, filtered, dried and blended with other additives to
produce the final product.
• The synthesis step involves reactions such as sulfonation,
halogenation, amination, diazotization, and coupling, followed
by separation process which includes distillation, precipitation,
and crystallization.

8. Synthesis of Dye
• In general, organic compounds such as naphtha are reacted with an
acid or an alkali along with an intermediate (such as a nitrating or a
sulfonating compound) and a solvent to form an intermediate
product.
• The intermediate products, based on their nature are coupled as
chromogen-chromophore and auxochrome.
• The dye thus formed is then separated from the mixture and purified.
• On completion of the manufacture of actual color, finishing
operations, including drying, grinding, and standardization, are
performed; these are important for maintaining consistent product
quality.

9. Classification of Dyes

10. Types of Dyestuff Manufactured
in India
• Dyes highly consumed in India are vat dyes, disperse dyes,
reactive dyes, azoic, acid and direct dyes ( 78 Dye and Dye
intermediate industries in Vapi).
• Disperse and reactive dyes constitute the largest product
segments in the country constituting nearly 45% of dyestuff
consumption.
• Vat dyes are superior to reactive dyes, but are almost ten times
more expensive.

12. Application of Dyes in Textile Industry
• Dyes and its intermediates are specifically used to make the textiles
decorative and attractive. Pigments, on the other hand, are insoluble and
are important inputs to products such as paints.
• Globally, the textiles sector consumes around 80% of the total
production due to high demand for polyester and cotton.
• With the change in the product profile of the textile industry from the
high-cost cotton textiles to the highly durable and versatile synthetic
fibers, the consumption pattern of dyes has also been changing.
• Polyesters are projected to account for a large part of dye consumption
in the country.
• Accordingly, disperse dyes, which find application in polyesters, are
projected to grow faster.

13. Areas of Application of Dyes in the
Textiles Industry
Group Application
Acid Wood, silk, paper, synthetic fibres, leather, nylon
Azoic Printing inks and pigments,
Basic Silk, wood, cotton, Polyster, nylon
Direct Cotton, cellulosic and blended fibres
Disperse dyes Synthetic fibres , Polyster
Reactive Cellulosic fibres and fabric
Organic pigments Cotton, cellulosic, blended fabric and paper
Sulfur Cotton and cellulosic fibres
Vat dyes Cotton, cellulosic and blended fibres
Source: Industrial waste water treatment, A. D. Patwardhan

14. Waste Generation
• The dyes and dye intermediate industries sector are one of the most
polluting industrial sectors.
• The waste generated from this sector is highly toxic/hazardous, difficult
to treat and very large in quantum.
• It has been reported that for manufacturing of one ton of product
approximately 5.5 tons of waste is generated. (Source: Sectoral Guidance
Manual Series; dye & dye intermediates by GCPC).
• The quantum of wastewater generated per ton of dyestuff production is
very low compared to that generated per ton of dye intermediate
production.
• The specific wastewater generation for major dye intermediates is about
15-20 m3/ton of product.

15. The causes of severe pollution generation from this sector
dominated by SSIs are:
• Multistage batch operations
• Poor process control of the unit operations/ processes
• Poor housekeeping practices
• Use of obsolete technology
• Poor or no recovery of by-products
• Excessive use of reactants, solvents and utilities
• Poor quality control
• Poor maintenance and record keeping
• Unskilled / untrained workers

16. Sources of Wastewater
• Mother liquor or filtrate streams from filtration
operations
• The wastewater streams from the washing of filter cake
to remove either salt impurities or residual filtrate adhere
from the cake
• Leakage and spillage
• Floor washing of the work area

17. Characteristics of Wastewater
• The effluent discharged is highly acidic and contains toxic compounds;
many of them are carcinogenic and highly hazardous to human health
and the environment.
• This is due to the presence of benzene, naphthalene and other nitro-
aromatic based compounds in the wastewater, which are used as raw
materials during the production of dye intermediates.
• Due to the excess use of acid and alkali quantity, the wastewater contains
high concentration of inorganic salts that results in the high
concentration of TDS.
• Due to this, treatment of effluent is very difficult and highly expensive.
• Further, the discharge of colored effluents into water bodies affects the
sunlight penetration which in turn decreases both the photosynthetic
activity and dissolved oxygen levels.

19. Typical Characteristics of Wastewater from the
Production of Dyes and Dye Intermediates
Parameter Value
Colour Varying deep colours
pH 4 - 6
Chemical Oxygen Demand (COD) 50,000 - 1,00,000 mg/L
Total Dissolved Solids (TDS) 15,000 - 2,00,000 mg/L
BOD / COD ratio < 0.2
Sulfates 61,000 - 73,000 mg/L
Sodium 40,000 - 47,000 mg/L
Chlorides 16,000 - 20,000 mg/L
Source: Sectoral Guidance Manual Series; dye & dye intermediates by GCPC

20. Effluent discharge standard prescribed by MoEF
for dye and dye intermediate industries
Parameter Standard for Effluent (limiting conc.)
pH 6.0-8.5
COD 250 mg/L
BOD (3 days; 27oC) 100 mg/L
Temperature
Shall not exceed 5oC above the ambient temperature of
water in the receiving body
TSS 100 mg/L
Colour 400 Hazen units
Mercury (as Hg) 0.01 mg/L
Chromium (as Cr+6) 0.1 mg/L
Total chromium (as Cr) 2.0 mg/L
Copper (as Cu) 3.0 mg/L

21. Parameter Standard for Effluent
Zinc (as Zn) 5.0 mg/L
Nickel (as Ni) 3.0 mg/L
Lead (as Pb) 0.1 mg/L
Manganese (as Mn) 2.0 mg/L
Cadmium (as Cd) 2.0 mg/L
Chloride (as Cl)** 1,000 mg/L
Sulfate (as SO4)** 1,000 mg/L
Phenolic compounds (as C6H5OH) 1.0 mg/L
Oil and grease 10.0 mg/L
Bioassay test (to be conducted as per
IS:6582-1971)
90% survival of fish after 96 hours in 100% effluent
(Source: www.moef.nic.in/environmental_standards)

22. Effluent discharge standard prescribed by GPCB
Parameter CETP Inlet Norms GPCB Norms
pH 6.5-8.5 6.5-8.5
Temperature 400C 400C
Color (pt co. scale) in units - 100 units
Suspended Solids 300 mg/L 100 mg/L
Oil and Grease 10 mg/L 10 mg/L
Phenolic Compounds 1 mg/L 1 mg/L
Cyanides 0.2 mg/L 0.2 mg/L
Fluorides 2 mg/L 2 mg/L
Sulphides 2 mg/L 2 mg/L
Ammonical Nitrogen 50 mg/L 50 mg/L
Arsenic 0.2 mg/L 0.2 mg/L
Total Chromium 2 mg/L 2 mg/L
Hexavelent Chromium 0.1 mg/L 0.1 mg/L
Copper 3 mg/L 3 mg/L

23. Parameter CETP Inlet Norms GPCB Norms
Lead 0.1 mg/L 0.1 mg/L
Mercury 0.01 mg/L 0.01 mg/L
Nickel 3 mg/L 3 mg/L
Zinc 5 mg/L 5 mg/L
Cadmium 2 mg/L 2 mg/L
Iron 3 mg/L 3 mg/L
BOD( 5 days at 200C 400 mg/L 30 mg/L
COD 1000 mg/L 250 mg/L
Chlorides 600 mg/L 600 mg/L
Sulphates 1000 mg/L 1000 mg/L
Total dissolved solids 2100 mg/L 2100 mg/L
Insecticides/Pesticides Absent Absent
Sodium adsorption ratio 26 26
Sodium percent 60 60
Bio-assay test -------
90% survival of fish after 96
hours in 100% effluent.
(Source: Standards for CETP as per, (Environment Protection Rules, 1986) & GPCB
Effluent norm.)

24. Wastewater Treatment Levels and
Processes
Treatment
Level
Description Process
Preliminary Removal of large solids such as rags, sticks, grit
and grease that may damage equipment or result in
operational problems
Physical
Primary Removal of floating and settleable materials
such as suspended solids and organic matter,
removal of heavy metals, partial removal of color,
partial removal of ammonical nitrogen, COD
Physico -
chemical
Secondary Removal of biodegradable organic matter and
suspended solids, Removal of Ammonical
Nitrogen by nitrification and denitrification
Biological
Tertiary/
advanced
Removal of residual COD, Colour, Ammoniacal
Nitrogen, suspended solids, refractory COD
Physico -
chemical
24

25. Major Treatment units in ETP
Preliminary Treatment Secondary Treatment
• Screens
• Detritor/scrapers
• Grit Chamber
• Skimming Tanks
• Aeration
• Activated Sludge Process (ASP)
• Trickling Filter
• Aerated Lagoons
• UASB
• Multiple Evaporator (ME) Plant
• Rotating Biological Contactors
(RBC)
Primary Treatment Tertiary Treatment
• Sedimentation/ Settling tank
• Clarifloculator
• Equalization Tank
• Neutralization Tank
• Sand/ Membrane Filters
• Activated Carbon Filters
• Disinfection
• Ion-exchange/ESP
• Nutrient Removal

26. Conventional ETP
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27. Dye Wastewater treatment Technologies

28. Colour in Effluent
• Dye wastes represent one of the most problematic groups of
pollutants because they can be easily identified by the human
eye and are not easily biodegradable.
• The process for the treatment of dye waste and colour removal
includes biological treatment, Catalytic oxidation, Membrane
filtration, Coagulation and flocculation and Adsorption
process.
• Various researches for colour removal by polymer coagulation
and adsorption has been investigated.

29. 1. Treatment with Polymer
Coagulation
• Sihorvala and Reddy- Used cationic polymer Catfloc-T, anionic
polymer APH-35 with alum and ferric chloride for treating cotton textile
waste.
• Namasivayam and Chandrasekharan- studied removal of color due to
reactive dyes such as congo red, tropeoline, brilliant green, methylene
blue and methyl violet from dye industry waste water.
They used Fe3+/Cr3+ sludge from fertilizer factory and red mud from
aluminium factory as flocculant and adsorbent.
Color removal for different flocculant was around 90%-97%.
• Bhole and Pawel- used anionic, cationic and non-ionic polyelectrolytes,
along with alum, aluminium chloride, ferric chloride, ferric sulphate and
mangesium chloride s coagulents, for color removal from a textile mill
dyeing waste.
With 300 mg/L of optimum dose of lime, the overall color removal was
97.5%, suspended solids 84% and COD removal 97.1%.

30. 2. Adsorption
• Rao N., s. Lathasree et al- have found high degree of
removal of azo dyes, viz. acid orange 7 and direct red 31, at
pH 7 with activated carbon.
• Namasivayam and Sumithra- Used waste Fe3+/ Cr3+ sludge
from petrochemical industry as adsorbent for removal of Acid
brilliant blue and Procion red (reactive azo dyes) and found
adsorptive capacities for the two dyes as 10.37 and 3.28 mg/g
of adsorbent.
• Ganjidoust- used a mineral soil as adsorbent for removal of
Benzonerol Black VSF 600 and Kayarus Supra Yellow RL.
• Other Adsorbents such as Flyash, Coal, Species of fungi can
be used for color removal.

31. Ammonical Nitrogen in Effluent
• Ammonia-nitrogen is a constituent in raw domestic
wastewater. Through the biological nitrification process,
ammonia is oxidized to nitrite and nitrate by aerobic
autotrophic bacteria.
• Industries such as Fertilizer, Pharmaceuticals, Dye and Dye
Intermediates and Pesticides having high content of
Ammonia-nitrogen in their effluent streams.
• Nitrification is affected by a number of environmental factors
including pH, toxicity, metals, and unionized ammonia.

32. Methods for Ammonical Nitrogen
Reduction
• Technologies for Ammonical Nitrogen reduction
 Ammonia stripping and distillation
 Ammonia precipitation as struvite (MAP crystals).
 Ion exchange for ammonia and nitrate removal
• Chemical oxidation of ammonia
 Ammonia and chloramines removal by Activated Carbon
 Breakpoint chlorination for ammonia removal
 Advanced oxidation processes

33. Solid Waste
• Large quantities of solid waste are generated from the dyes industry.
• The sources of waste generation are both from the process itself as well as
from the treatment of wastewater.
• Disposing off such large volumes of hazardous waste entails a huge cost
to the individual SSI as well as the industry as a whole.
• Solid waste generated in the process of the production and industrial use
of synthetic dyes, dye intermediates and pigments account for 26% of the
entire volume of hazardous waste sent to TSDF for hazardous waste in
the State of Gujarat.
• Large quantum of gypsum sludge is generated from the primary treatment
of acidic wastewater, where lime is used for neutralization.

34. • The types of wastes from the process include gypsum sludge, iron
sludge, residues from the filter press, tarry waste, waste dye
powder and packaging material.
• All types of waste generated from the dyes and dye intermediate
sector comes under the category of hazardous waste.
• As per the Hazardous Waste (Management and Handling) Rules
1989, hazardous waste has to be disposed off in a secured landfill
facility.
• Except tarry waste, which has to be incinerated, all other types of
solid wastes generated through this industry have to be disposed in
secured landfills after physical treatment.
• The MoEF also mandates specific emission standards for
incinerators for this industry.

35. Gaseous Emissions
• The major gaseous emissions from the dyes and dye intermediate
industry are unrecovered gases generated from the process.
• Gaseous emissions contain gases like chlorine, sulfur dioxide,
sulfur trioxide, nitrogen oxides and fumes of acid and organic
solvents.
• If these gases are not recovered and marketed as by-products, they
pose a serious pollution threat.
• The other source of air pollution from this sector is the particulate
matter emission from the drying and grinding operations.
• Flue gas from boilers is also a source of air pollution.

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