Textile Effluent
Textile effluent and its management
Every country is aiming at Common Effluent Treatment Plants for the development of zero discharge solutions for the bleaching and dyeing units. The total effluent treatment capacity is designed based on the Mill size, based on the effluents generated in these mills.
Selection of technology and design for the engineering for the CETP is Pipeline for effluent conveyance, Pre‐treatment works, Reverse Osmosis plant, Evaporator plant, Recovered water distribution system and many more advanced technologies.
Textile Effluents and its management
- As textile industry is one of the largest industries in the world and different fibers such as cotton, silk, wool as well as synthetic fibers are all pre‐treated, processed, colored and after being treated using large amounts of water and a variety of chemicals, there is a need to understand the chemistry of the textile effluents very
- The textile waste characteristic needs to be understood clearly
- Different methods and aspects of Textile Effluents and their management to save the environment from polluting the same needs to be understood
- Major pollutants in textile wastewaters are high suspended solids, chemical oxygen demand, heat, color, acidity, and other soluble substances whose chemistry will be emphasized
ETP Process Design for a Textile factory
Introduction
The textile industry is one of the largest and most complicated industrial chains in the manufacturing industry. The production of a textile requires several stages of mechanical processing such as spinning, knitting, weaving, and garment production, which seem to be insulated from the wet treatment processes like sizing, de-sizing, scouring, bleaching, mercerizing, dyeing, printing, and finishing operations, but there is a strong interrelation between dry processes and consecutive wet treatments. The textile industry emits a wide variety of pollutants from all stages in the processing of fibers, fabrics, and garment production
Stages of Textile Processing
Textile industry Share
| Country | Value in ($ billion) | Share (%) |
|---|---|---|
| China | 94.4 | 32.1 |
| EU27 | 76.6 | 26.1 |
| India | 15.0 | 5.1 |
| United States of America | 13.8 | 4.7 |
| Korea Republic | 12.4 | 4.2 |
| Turkey | 10.8 | 3.7 |
| Pakistan | 9.1 | 3.1 |
| Indonesia | 4.8 | 1.6 |
| Vietnam | 3.8 | 1.3 |
| Bangladesh | 1.6 | 0.5 |
| Rest of the World | 51.7 | 17.5 |
| Total | 294 | 99.9 |
Textile production flow diagram
List of harmful Chemicals used in Textile Industry
- Detergents mainly nonyl‐phenol ethylates‐ generates toxic metabolites which is poisonous to fish
- Stain remover: Carry solvents like CCl4 can cause ozone depletion
- Oxalic acid used for rust stain removal: are toxic to aquatic organisms and also boots COD
- Sequestering agents: Polyphosphates like Trisodium polyphosphate and sodium hexametaphosphate: are banned chemicals
- Printing gums: preservatives like pentachlorophenol can cause dermatitis, liver and kidney damage are all banned chemicals
- Fixing agent: Formaldehyde and Benzidine are banned internationally
- Bleaching: Chlorine bleaching caused itching and is harmful
- Dyeing: Azo dyes which release amines are banned because they are known carcinogens
Textile Waste Characteristics
The pollutant features of textile wastes differ widely among various Organic substances such as dyes, starches, and detergents in effluent undergo chemical and biological changes which consume dissolved oxygen from the receiving stream and destroy aquatic life
Such organics should be removed to prevent septic conditions and avoid rendering the stream water unsuitable for municipal, industrial, agricultural and residential uses.
| Process | Wastewater | Solid Wastes | Emission |
|---|---|---|---|
| Fiber preparation | Little or none | Fiber waste and packaging waste | Little or none |
| Yarn spinning | Little or none | Packaging wastes, sized yarn, fiber waste, cleaning, and processing waste | Little or none |
| Sizing | BOD, COD, metals, cleaning waste, size | Fiber lint, yarn waste, packaging waste, unused starch-based sizes |
VOCs |
| Weaving | Little or none | Packaging waste, yarn, and fabric scraps used oil | Little or none |
| Knitting | Little or none | Packaging waste, yarn, and fabric scraps | Little or none |
| Tufting | Little or none | Packaging waste, yarn, and fabric scraps, off-spec fabric | Little or none |
| Desizing | BOD from sizes lubricants, biocides, anti-static compounds |
Packaging waste, fabric lint, yarn waste, cleaning and maintenance materials | VOCs from glycol esters |
| Scouring | Disinfectants, insecticide residues, NaOH, detergents oils, knitting lubricants, spin finishes, spent solvents | Little or none | VOCs from glycol esters and scouring solvents |
| Bleaching | H2O2, stabilizers, high pH | Little or none | Little or none |
| Singeing | Little or none | Little or none | Small amounts of exhaust gasses from the burners exhausted with components |
| Mercerizing | High pH, NaOH | Little or none | Little or none |
| Heat setting | Little or none | Little or none | Volatilization of spin finish agents- synthetic fiber manufacture |
Types of textile waste produced
| Process | Possible Pollutants | Nature of Effluent |
|---|---|---|
| Desizing | Starch, glucose, PVA, resins, fats, and waxes do not exert a high BOD. |
Very small volume, high BOD (30-50% of total), PVA. |
| Kiering | Caustic soda, waxes, soda ash, sodium silicate, and fragments of cloth. |
Very small, strongly alkaline, dark color, high BOD values (30% of total) |
| Bleaching | Hypochlorite, chlorine, caustic soda, hydrogen peroxide, acids. | Small volume, strongly alkaline, low BOD (5% of total) |
| Mercerizing | Caustic soda | Small volume, strongly alkaline, low BOD (Less than 1% of total) |
| Dyeing | Dyestuff, mordant, and reducing agents like sulfides, acetic acids and soap |
Large volume, strongly colored, fairly high BOD (6% of total) |
| Printing | Dye, starch, gum oil, china clay, mordants, acids, and metallic salts | Very small volume, oily appearances, fairly high BOD. |
| Finishing | Traces of starch, tallow, salts, special finishes, etc. | Very small volume, less alkaline, low BOD. |
Sources of water pollution at various stages of processing.
Textiles and Garments are one of the oldest and largest industries in the world. The textile industries have great economic significance by virtue of their contribution to overall industrial output and employment generation in so many countries. The textile industry utilizes various dyes, chemicals, and large amounts of water during the production process. The wastewater produced during this process contains a large number of dyes and chemicals containing trace metals such as Cr, As, Cu, and Zn which are capable of harming the environment and human health. The textile wastewater causes hemorrhage, ulceration of skin, nausea, skin irritation, and dermatitis. The chemicals present in the water block the sunlight and increase the biological oxygen demand thereby inhibiting the photosynthesis and reoxygenation process
| Country | Value ($ Billion) | Share (%) |
|---|---|---|
| China | 94.4 | 32.1 |
| European Union 27 | 76.6 | 26.1 |
| India | 15.0 | 5.1 |
| United States of America | 13.8 | 4.7 |
| Korea Republic | 12.4 | 4.2 |
| Turkey | 10.8 | 3.7 |
| Pakistan | 9.1 | 3.1 |
| Indonesia | 4.8 | 1.6 |
| Vietnam | 3.8 | 1.3 |
| Bangladesh | 1.5 | 0.5 |
| Rest of the World | 51.7 | 17.5 |
| Total | 294 | 99.9 |
Major Exporters of Textiles
| Country | Value ($ Billion) | Share (%) |
|---|---|---|
| China | 153.8 | 35.6 |
| European Union 27 | 116.4 | 27.1 |
| Bangladesh | 19.9 | 4.6 |
| India | 14.4 | 3.3 |
| Turkey | 13.9 | 3.2 |
| Vietnam | 13.2 | 3.1 |
| Indonesia | 8.0 | 1.8 |
| United States of America | 5.2 | 1.2 |
| Pakistan | 4.6 | 1.1 |
| Korea Republic | 1.8 | 0.4 |
| Rest of the World | 79.8 | 18.5 |
| Total | 431 | 99.9 |
Water consumption in textile industries, by type of fabrics
| Fabric | Water consumption (kg/kg) |
|---|---|
| Cotton | 250-350 |
| Wool | 200-300 |
| Nylon | 125-150 |
| Rayon | 125-150 |
| Polyester | 100-200 |
| Acrylic | 100-200 |
Water consumption in textile industries, by type of process
| Process | Water consumption (%) |
|---|---|
| Bleaching, finishing | 38 |
| Dyeing | 16 |
| Printing | 8 |
| Boilerhouse | 14 |
| Humidification (Spinning) | 6 |
| Humidification (weaving) | 9 |
| Sanitary, Domestic | 9 |
Textile Wastewater Problem
- Treatment of wastewater – will definitely reduce the waste, prevent and make positive effects on its further uses
- Strong rinse waters from dye operations may be used to make up new dyebaths, while weak rinses may be recycled through in‐plant water treatment units
- The savings in the material in the first case may be enough to pay for the cost of treatment of the latter case
Chemicals used in Textile Industry
- Synthetic organic dyes, bleaches, and detergents Some chemicals are biodegradable‐ starch, however, others such as dyes are non-biodegradable Thus the effluents could have lower dissolved oxygen concentrations which means higher BOD and COD
- Solids in textile wastewater come from the fibrous substrate and process chemicals, this disturbs the aquatic life by showing oxygen transfer and reducing light penetration
Inorganic chemicals
- High concentrations of soluble inorganic salts may make the discharge water stream unsuitable for industrial and municipal use
- Metals such as chromium and zinc are toxic to aquatic life and should be removed before discharge
- Certain carrier chemicals used in dyeing, such as phenol may add bad taste and odor as well.
Effluent characteristics from the typical textile industry
| Process | Composition | Nature |
|---|---|---|
| Sizing | Starch, waxes, carboxymethyl cellulose, polyvinyl alcohol. | High in BOD & COD |
| Desizing | Starch, waxes, carboxymethyl cellulose, polyvinyl alcohol. | High in BOD, COD, suspended solids, dissolved solids. |
| Scouring | Caustic soda, waxes, grease, soda ash, sodium silicate, fibers, surfactants, sodium phosphate. | Dark-colored, High pH, COD, dissolved solids. |
| Bleaching | Hypochlorite, Caustic soda, sodium silicate, hydrogen peroxide, surfactants, sodium phosphate. |
Alkaline suspended solids. |
| Mercerizing | Caustic soda. | High pH, low COD, high dissolved solids. |
| Dyeing | Various dyes, mordants, reducing agents, acetic acid soap | Strongly colored, High COD, dissolved solids, low SS |
| Printing | Pastes, starch, gums, oil, mordants, acids, soaps. | Highly-colored, High COD, oily appearance, SS |
| Finishing | Inorganic salts. | Slightly Alkaline, low BOD. |
Wastewater characteristics: Process-wise
Important Characteristics of Wastewater from Textile Industry
| Parameter | Range |
|---|---|
| pH | 6-10 |
| Temperature (°C) | 35-45 |
| Total d solids (mg/L) | 8,000-12,000 |
| BOD (mg/L) | 80-6,000 |
| COD (mg/L | 150-12,000 |
| Total suspended solids (mg/L | 15-8,000 |
| Total dissolved solids (mg/L) | 2,900-3,100 |
| Chlorine (mg/L) | 1,000-6,000 |
| Free chlorine (mg/L) | <10 |
| Sodium (mg/L) | 70% |
| Trace metals (mg/L | |
| Fe | <10 |
| Zn | <10 |
| Cu | <10 |
| AS | <10 |
| Ni | <10 |
| B | <10 |
| F | <10 |
| Mn | <10 |
| V | <10 |
| Hg | <10 |
| PO4 | <10 |
| Co | <10 |
| Oil and Grease (mg/L) | 10-30 |
| TNK (mg/L | 10-30 |
| NO3-N (mg/L | <15 |
| Free Ammonia (mg/L | <10 |
| Sulphate (mg/L | 600-1000 |
| Silica (mg/L | <15 |
| Total Kjeldahl Nitrogen (mg/L | 70-80 |
| Color (Pt-Co) | 50-2,500 |
Some Textile wastewater pollution regulations are imposed by several countries.
| Parameter | CC ME | China | BIS | Hong Kong | FEPA | ME X | THA | PHI | IN DO | BD | SL |
|---|---|---|---|---|---|---|---|---|---|---|---|
| pH | 6.5- 8.5 |
6-9 | 5.5- 9 |
6-10 | 6-9 | 6- 8.5 |
5-9 | 6-9 | 6-9 | 6.5-9 | 6- 8.5 |
| Temperature (°C) |
30 | – | 50 | 43 | 40 | – | – | 40 | – | 40-45 | 40 |
| Color (Pt-Co) | 100 | 80 | Non e | 1 (Lovibon d) |
1 (Lovibon d) |
– | – | 100- 200 |
– | – | 30 |
| TDS (mg/L) | 200 0 |
– | 2100 | – | 2000 | – | 2000- 5000 |
1200 | – | 2100 | 21 00 |
| TSS (mg/L) | 40 | 150 | 100 | 800 | 30 | – | 30-150 | 90 | 60 | 100 | 50 0 |
| Sulphide (mg/L) |
200 | 100 0 |
2000 | 1000 | 200 | – | – | – | – | 1000 | 20 00 |
| Free Chlorine (mg/L) |
100 0 |
– | 1000 | – | 1000 | – | – | 1000 | – | – | – |
| COD (mg/L) | 80 | 200 | 250 | 2000 | 80 | <12 5 | 120- 400 |
200- 300 |
250 | 200 | 60 0 |
| BOD (mg/L | 50 | 60 | 30 | 800 | 50 | <30 | 20-60 | 30-200 | 85 | 150 | 20 0 |
| Oil and Grease (mg/L) |
– | – | 10 | 20 | 10 | – | 300 | 5-15 | 5 | 10 | 30 |
| Dissolved Oxygen (mg/L) |
600 0 |
– | – | ³4000 | – | – | – | 1000- 2000 |
– | 4500- 8000 |
– |
| Nitrate (mg/L) | 130 00 |
– | 1000 0 |
– | 20000 | 100 00 |
– | – | – | 10000 | 45 00 0 |
| Ammonia (mg/L) |
0.1 | – | – | 500 | 0.2 | – | – | – | – | 5000 | 60 |
| Phosphate (mg/L) |
<40 00 | 100 0 |
500 0 |
5000 | 5000 | – | – | – | 200 0 |
– | 20 00 |
| Calcium (mg/L) | – | – | – | – | 20000 | – | – | 20000 | – | – | 24 00 0 |
| Magnesium (mg/L) | 200 00 |
– | – | – | 20000 | – | – | – | – | – | 15 00 0 |
| Chromium (mg/L) |
1 | – | 100 | 100 | <100 | 50 | 500 | 50-500 | 500 | 2000 | 50 |
| Aluminium (mg/L) |
5 | – | – | – | <1000 | 500 0 |
– | – | – | – | – |
| Copper (mg/L) | <10 00 | 200 0 |
300 0 |
1000 | <1000 | 100 0 |
1000 | 1000 | 200 0 |
500 | 30 00 |
| Manganese (mg/L) |
5 | 200 0 |
2000 | 1000 | 5.0 | 200 | 5000 | 1000- 5000 |
– | 5000 | 50 0 |
| Iron (mg/L) | 300 | – | 300 0 |
500 | 20000 | 100 0 |
– | 1000- 20000 |
500 0 |
2000 | 10 00 |
| Zinc (mg/L) | 30 | 500 0 |
500 0 |
1500 | <10000 | 100 00 |
– | 5000- 10000 |
500 0 |
5000 | 10 00 0 |
| Mercury (mg/L) | 0.0 26 |
– | 0.01 | 1 | 0.05 | – | 5 | 5 | – | 10 | 1 |
Note: CCME-Canadian Council of Ministers of the Environment, BIS-Bureau of Indian Standards, FEPA-Federal Environmental Protection Agency (USA), Mex-Mexico, Tha- Thailand, Phi-Philipines, Indo-Indonesia, Bd- Bangladesh SL-Srilanka
The removal of the processing units.
| Items | Raw Water (regulating | Biochemical treatment system | Physiochemical treatment system | ||
|---|---|---|---|---|---|
| tank) | Effluen t | Removal rate | Effluent | Removal rate | |
| pH | 8-12 | 7-8 | 6-9 | ||
| CODcr (mg/L) | 1000-2000 | 100- 200 |
90 | £100 | 50 |
| BOD5 (mg/L | 300-600 | 15-30 | 95 | £30 | |
| Color (times) | 100-600 | 60 | 80 | £40 | 35 |
PERMISSIBLE STANDARDS IN INDIA
| S.No. | Parameter | Permissible limits (disposal to inland surface water) |
|---|---|---|
| 1 | pH | 5.5 to 9.0 |
| 2 | TSS | <100 mg/l |
| 3 | Oil & Grease | <10 mg/l |
| 4 | BOD | <30 mg/l |
| 5 | COD | <250 mg/l |
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