Textile Manufacturing Process, Pollution and Pollution Control
Contents Topic Name
Page No
Introduction
01
Materials Raw of Textile Process
01
Textile Manufacturing Process
02-04
Water Consumption Pattern of Textile Industry
05
Textile Wastewater or Effluent
06
Physical Characteristics
06-07
Chemical Characteristics
08-09
Classification of Textile Waste water in Textile Industry
10
Effluent Characteristics of Textile Industry Processes
11
Water Pollution and Textile Effluent
12
Treatment of Wastewater
13
Conclusion
13
References
14
Textile Manufacturing Process, Pollution and Pollution Control
Introduction The industrial development is essential for socio-economic existence of a nation. The environment with its biotic and abiotic components provides basic resources that support production consumption by population and assimilates the residues produced during these activities. The major environmental issues related to industrial development are over exploitation of natural resources and environmental pollution. Therefore, the protection of environment and natural resources is a must for the proper development of a country. Industrial wastes are comprised of different types of solid waste, liquid waste, hazardous waste and gaseous waste .The characteristics of industrial waste are different from municipal and commercial wastes. They contain a huge amount of inorganic, organic and organometallic substances that discharge from the individual sources and mix into Human Environment. The liquid form of the industrial waste is termed effluent. Environmental pollution due to different types of industries is one of the vital problem presently facing the India and all over the world. Textile industries are major sources of Environmental pollution. As the textile industries consume large quantities of water and generates waste water in proportionate order.
Materials Raw of Textile Process ∆ Yarn ∆ Fabric ∆ Dye stuff ∆ Chemical and auxiliaries
Textile Manufacturing Process, Pollution and Pollution Control 1
Textile Manufacturing Process Textile manufacturing or production is a very complex process. The range of textile manufacturing is so long. It starts from fiber to finished products.
Spinning ↓ Weaving ↓ Dyeing +Printing +Finishing ↓ Garments Manufacturing
Spinning Blowroom Carding Drawing Combing Drawing Roving Manufacturing Ring Spinning Weaving Yarn from spinning section Doubling and Twisting Winding Creeling Warping Sizing Winding on weavers beam Weaving Dyeing
Inspection of grey cloth Stitching Cropping Brushing Singeing Desizing
Textile Manufacturing Process, Pollution and Pollution Control 2
Scouring Bleaching Souring Washing Drying Mercerizing Dyeing After treatment Finishing Inspection Packing Baling
Printing
Inspection of grey cloth Stitching Cropping Brushing Singeing Desizing Scouring Bleaching Souring Washing Drying Mercerizing Dyeing After treatment Finishing Inspection Packing Baling
Garment Manufacturing
Design / Sketch Pattern Design Sample Making Production Pattern Grading Marker Making Spreading Cutting Sorting/Bundling Sewing/Assembling
Textile Manufacturing Process, Pollution and Pollution Control 3
Inspection Pressing/ Finishing Final Inspection Packing Despatch
Figure: Cotton Textile Goods Textile Manufacturing Process, Pollution and Pollution Control 4
Water Consumption Pattern of Textile Industry Major contribution of the raw effluent are from the sizing & desizing, scouring, dyeing & bleaching, mercerizing section of the industry. Apart from these main unit operations, a substantial quantity of effluent is generated from the humidification section. Concentration of pollutants and quantity of effluent from these sections may vary depending upon the scale of production, chemicals used and technologies adopted. Following table may give an idea for raw water requirement in similar type of industries. Water loss is approximately 20% mainly from the humidification section.
Figure: Water Consumption in wet processing of Textile Sl. No.
Product
Quantity of water required
1
Denim
30-35 litres per meter of cloth.
2
Knitting fabric *
90 litres per Kg of fabrics produced.
3
Shirting section
110 litres per meter.
4
Trousers
80 Litres per meter of cloth produced.
Table: Quantity of water required
Textile Manufacturing Process, Pollution and Pollution Control 5
Textile Wastewater or Effluent Textile wastewater includes a large variety of dyes and chemical additions that make the environmental challenge for textile industry not only as liquid waste but also in its chemical composition. Main pollution in textile wastewater comes from dyeing and finishing processes. These processes require the input of a wide range of chemicals and dyestuffs, which generally are organic compounds of complex structure. Water is used as the principal medium to apply dyes and various chemicals for finishes. Because all of them are not contained in the final product, became waste and caused disposal problems. Major pollutants in textile wastewaters are high suspended solids, chemical oxygen demand, heat, color, acidity, and other soluble substances. Substances which need to be removed from textile wastewater are mainly COD, BOD, nitrogen, heavy metals and dyestuffs.
Physical Characteristics The principal physical characteristics of wastewater are its ∆ Solids content- The total solids in a wastewater consist of the insoluble or suspended solids and the soluble compounds dissolved in water. The suspended solids content is found by drying and weighing the residue removed by the filtering of the sample. When this residue is ignited the volatile solids are burned off. Volatile solids are presumed to be organic matter, although some organic matter will not burn and some inorganic salts break down at high temperatures. ∆ Color- Color is a qualitative characteristic that can be used to assess the general condition of wastewater. Wastewater that is light brown in color is less than 6 h old, while a light-to- medium grey color is characteristic of wastewaters that have undergone some degree of decomposition or that have been in the collection system for some time. ∆ Odor-The determination of odor has become increasingly important, as the general public has become more concerned with the proper operation of wastewater treatment facilities. The odor of fresh wastewater is usually not offensive, but a variety of odorous compounds are released when wastewater is decomposed biologically under anaerobic conditions ∆ Temperature-The temperature of wastewater is commonly higher than that of the water supply because warm municipal water has been added. The measurement of temperature is important because most wastewater treatment schemes include biological processes that are temperature dependent.
Textile Manufacturing Process, Pollution and Pollution Control 6
.
Table: DOE Standards for Industrial Discharge
Figure: This figure shows the physical characteristics of industrial wastewater
Textile Manufacturing Process, Pollution and Pollution Control 7
Chemical Characteristics The principal chemical characteristics of wastewater are its ∆ Inorganic chemicals-The principal chemical tests include free ammonia, organic nitrogen, nitrites, nitrates, organic phosphorus and inorganic phosphorus. All living organisms require varying amounts of some trace elements, such as iron, copper, zinc and cobalt, for proper growth. ∆ Organic chemicals-Laboratory methods commonly used today to measure gross amounts of organic matter in wastewater include (1) biochemical oxygen demand (BOD), (2) chemical oxygen demand (COD) and (3) total organic carbon (TOC). ∆ Volatile Organic Carbons (VOC)-Volatile organic compounds (VOC) such as benzene, toluene, xylenes, dichloromethane, trichloroethane and trichloroethylene, are common soil pollutants in industrialized and commercialized areas. One of the more common sources of these contaminants is leaking underground storage tanks.
∆ Heavy metals- It can be seen that of all of the heavy metals chromium is the most widely used and discharged to the environment from different sources. Mercury generates a great deal of concern as a heavy-metal pollutant. Mercury is found as a trace component of many minerals, with continental rocks containing an average of around 80 ppb, or slightly less, of this element. Lead from leaded gasoline used to be a major source of atmospheric and terrestrial lead, much of which eventually enters natural water systems. ∆ Inorganic pollutants and species-Hydrogen sulphide, H2S, is a product of the anaerobic decay of .organic matter containing sulphur. Cyanide ion, CN-, is probably the most important of the various inorganic species in wastewater. ∆ Organic pollutants and species- Soaps, detergents and associated chemicals are potential sources of organic pollutants. Others, such as refractory (degradation-resistant) organics (organ chlorides, nitro compounds etc.) and salts and heavy metals, are not efficiently removed.
Textile Manufacturing Process, Pollution and Pollution Control 8
Property
Standard
Cotton
Synthetic
Wool
pH
5.5 – 9.0
8-12
7-9
3-10
BOD, mg/l, 5 days
30-350
150-750
150-200
5000 – 8000
COD, mg/l, day
250
200-2400
400-650
10,000 – 20,000
TDS, mg/l
2100
2100-7700
1060-1080
10,000 –13,000
Table: Comparison with different parameters and Pattarns
Figure: This figure shows the chemical characteristics of industrial wastewater
Textile Manufacturing Process, Pollution and Pollution Control 9
Classification of Textile Waste water in Textile Industry
Textile waste is broadly classified into four categories, each of having characteristics that demand different pollution prevention and treatment approaches. Such categories are discussed in the following sections: Hard to Treat Wastes: This category of waste includes those that are persistent, resist treatment, or interfere with the operation of waste treatment facilities. Non-biodegradable organic or inorganic materials are the chief sources of wastes, which contain color, metals, phenols, certain surfactants, toxic organic compounds, pesticides and phosphates. The chief sources are: o -Color & metal → dyeing operation o -Phosphates → preparatory processes and dyeing o -Non-biodegradable organic materials → surfactants Hazardous or Toxic Wastes: These wastes are a subgroup of hard to treat wastes. But, owing to their substantial impact on the environment, they are treated as a separate class. In textiles, hazardous or toxic wastes include metals, chlorinated solvents, non-biodegradable or volatile organic materials. Some of these materials often are used for non-process applications such as machine cleaning. High Volume Wastes: Large volume of wastes is sometimes a problem for the textile processing units. These wastes sometimes can be reduced by recycle or reuse as well as by process and equipment modification. Most common large volume wastes include: -High volume of waste water -Wash water from preparation and continuous dyeing processes and alkaline wastes from preparatory processes -Batch dye waste containing large amounts of salt, acid or alkali.
Dispersible Wastes: The following operations in textile industry generate highly dispersible waste: -Waste stream from continuous operation -Print paste (printing screen, squeeze and drum cleaning) -Lint (preparatory, dyeing and washing operations) -Foam from coating operations -Solvents from machine cleaning -Still bottoms from solvent recovery (dry cleaning operation) -Batch dumps of unused processing (finishing mixes)
Textile Manufacturing Process, Pollution and Pollution Control 10
Effluent Characteristics of Textile Industry Processes Effluents from the textile industry commonly contains high concentrations of organic and inorganic chemicals and are characterized by high Chemical Oxygen Demand (COD), Biological Oxygen Demand (BOD), Total Dissolved Solids (TDS), pH, Total Suspended Solids (TSS) values and low Dissolved Oxygen (DO) value as well as strong color.
Process
Effluent Composition
Sizing
Starch, waxes, Carboxymethyl High in BOD, COD Cellulose (CMC), Polyvinyl Alcohol (PVA), wetting agents.
Desizing
Starch, CMC, waxes, pectins
Bleaching
Sodium Hypochlorite, NaOH, H2O2, acids,
PVA,
Pollutant Nature
fats, High in BOD, COD, dissolved solids (DS)
SS,
Cl2, High alkalinity, high SS
Surfactants, NaSiO3, Sodium Phosphate, short cotton fibre Mercerizing
Sodium Hydroxide, cotton wax
High pH, low BOD, high DS
Dyeing
Dyestuffs Urea, reducing strongly colored, high BOD, DS, agents, oxidizing agents, low SS, heavy Acetic acid, detergents,
Printing
Pastes, urea, starches, gums, Highly colored, high oils, binders, acids, BOD Oily, appearance, Thickeners, cross-linkers, slightly alkaline reducing agents, alkali
SS,
Source: Bruggen et al, 2001 and EPA, 1998 Textile Manufacturing Process, Pollution and Pollution Control 11
Water Pollution and Textile Effluent Textile wastewater includes a large variety of dyes and chemical additions that make the environmental challenge for textile industry not only as liquid waste but also in its chemical composition. Main pollution in textile wastewater comes from dyeing and finishing processes. These processes require the input of a wide range of chemicals and dyestuffs, which generally are organic compounds of complex structure. Water is used as the principal medium to apply dyes and various chemicals for finishes. Because all of them are not contained in the final product, became waste and caused disposal problems. Major pollutants in textile wastewaters are high suspended solids, chemical oxygen demand, heat, color, acidity, and other soluble substances. Substances which need to be removed from textile wastewater are mainly COD, BOD, nitrogen, heavy metals and dyestuffs.
Industry
Water
Pollution
Ranking
Pollution
Product
Agriculture
Moderate
1.08
3
Textile *
Big
3.35
1
Transport
Small
0.02
6
Construction
Small
0.14
5
Paper
Very big
0.67
4
Leather
Extreme
1.88
2
Sugar
Extreme
1.72
2
Table: Water pollution source and their ranking in Bangladesh
Textile Manufacturing Process, Pollution and Pollution Control 12
Treatment of Wastewater After every effort that may be made to reduce waste strength and volume, there still remains the problem of desposing the final remains of polluted waste into any water stream, thus the waste may be treated in various methods either singly or in combination and the best combination of methods differs from plant to plant. The various typs of treatment are as follows
Segregation Lagooning and Storage Screening Mechnecal Filtration Pre-aeration and Post-aeration Neutralization Chemical Precipitation Chemical Oxidation Biological Oxidation
Conclusion Characterization of textile process effluent streams is very important to develop strategies for water treatment and reuse. To optimize treatment and reuse possibilities, textile industry waste streams should be in principle considered separately. When the characteristics of the separate streams are known, it can be decided which streams may be combined to improve treatability and increase reuse options.As discussed textile sector is putting enormous impact on Bangladesh economy yet this industry is currently facing several challenges. Out of various activities in textile industry, chemical processing contributes about 70% of pollution. Waste stream generated in this industry is essentially based on water-based effluent generated in the various activities of wet processing of textiles. It is well known that wet processing mills consume large volume of water for various processes such as sizing, desizing, and scouring, bleaching, mercerization, dyeing, printing, finishing and ultimately washing. In fact, in a practical estimate, it has been found that 45% material in preparatory processing, 33% in dyeing and 22% are re-processed in finishing. But where is the real problem? The fact is that the effluent in textile generated in different steps is well beyond the standard and thus it is highly polluted and dangerous.
Textile Manufacturing Process, Pollution and Pollution Control 13
References C.M. Noorjahan., Physico-chemical Characterization of Untreated Textile Effluent and its Effects on Biochemical Constituents of Fresh Water Fish, Tilapia Mossambica, ISRJ, I (V), 1-11 (2011). N. L. Nemerow, Industrial Water Pollution Origins, Characteristics and Treatment, Addison Wesley, Reading, Massachusetts, 738 (1978). Environmental Protection Authority (EPA, 1998). Environmental Guidelines for the Textile dyeing and Finishing Industry, State Government of Victoria, Melbourne, Victoria, Australia. Guha, A. K. and Hoque, M. I. 2009. “Characterization of Textile waste water of Different Areas of Bangladesh” Bangladesh Textile Today, 2 (3): 16-20. Jamaluddin, A. M. and Nizamuddin, M. 2012.“Physicochemical Assessment of Textile Effluents in Chittagong Region of Bangladesh and Their Possible Effects on Environment”, International Journal of Research in Chemistry and Environment; 2(3): 220-230. Savin I., Butnaru R., (2009), Research on the Decrease of the Ecological Impact on Wastewater in the Textile Industry – Studies on the General Features of Wastewater in the Textile Industry, Bulletin of the Polytechnic Institute of Iaşi, in press. Bisschops, I. and Spanjers, H. (2003) Literature review on textile wastewater characterisation. Environ. Technol. vol. 24, pp. 1399-1411 Nemerow, N.L. (1978) Industrial Water Pollution: Origins, Characteristics and Treatment. Addison-Wesley, Reading, Massachusetts, pp 738.
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