Important Parameters of Water for Textile Wet Processing Industry By M.Taha Bin Yaseen M. Rahman Sajid Saleem Jafar M. Usama Gill

Outline• Water in Textile Industry.

• Major water consuming sectors in textile industry.

• Water Used For 100 Kg Cotton.

• Sources of Water.

• Important parameters for water to be used in textile wet processing.

• Desirable Water Quality Parameters for Textile Wet Processing.

• Disadvantages of Hard or Unsuitable water usage in textile processing.

• Conclusion.

Water in Textile Industry• The textile industry is the 3rd largest consumer of water in the world.

• Wet processing engineering is one of the major streams in textile engineering refers to textile chemical processing.

• Water is the most common and vital solvent for wet processing.

• Water containing impurities that are not useful, so it would affect our textile wet process and cause a defect in the form of shade variation, unevenness and damaging of textile material.

• Therefore, the quality of water should be necessarily maintained for better performance.

Major water consuming sectors in textile industry

Sizing/De-sizing

Scouring

Bleaching

Dyeing

Printing

Finishing

Washing

Mercerization

Total water consumed during wet processing

Process Percent water consumed

Bleaching 38%

Dyeing 16%

Printing 8%

Boiler 14%

Other Uses 24%

Water Used For 100 Kg Cotton

Process

• Sizing

• Desizing

• Kierring

• Mercersing

• Scouring

• Bleaching

• Direct

• Vat

• Reactive

Water in litre

• 700

• 1500

• 1100

• 4500

• 3000

• 1000

• 5000

• 15000

• 5000

Sources of WaterWater Source

pH Total Hardness

(ppm)

Salinity Total Dissolved

Solid(mg/L)Lake Water 7.2 900 0.1 272

Sea Water 7.7-8.0 1000 42.3 38.5

Spring Water 5.5 700 0.01 89

Grey Water 8.0 960 0.1 286

Irrigation Water

6.0 125 0.001 125

Rain Water 5 50 0.3 122

Parameters for water

Important parameters for water to be used in textile wet processing• Color

• Turbidity

• pH value

• Alkalinity

• Acidity

• Salinity Content

• Total Dissolved Solids(TDS)

• Total Suspended Solids(TSS)

• Specific Conductivity

• Total Hardness

• Temperature

• Iron Content

Color• Color normally indicates the presence of soluble and suspended

matter , which affects the textile wet processing .

• The color of water is measured in terms of Hazen units, by comparing it with a color of a standard solution.

Hazen Unit: The color produced by dissolving 1 ppm platinum in the form of chloroplatinic acid , in the presence of 2 ppm cobalt chloride.

Turbidity• Turbidity is caused by the scattering of light by suspended particles

which may be organic or inorganic in nature. • The turbidity of water is measured against a standard solution having a

standard turbidity value 1000 units.

pH Value• In all textile processes in which aqueous solutions are used, balancing

the pH of the solution is primary.• The pH of a textile is logically defined in terms of the hydrogen ions

concentration of the water present in the cloth.

Acidity

• The alkalinity is due to the presence of bicarbonates , carbonates or hydroxides.

• Alkalinity is divided into caustic alkalinity ( above pH 8.2) and total alkalinity above pH 4.5.( Bicarbonate and caustic alkalinity).

Alkalinity

• Most natural waters are buffered by a CO2 / HCO3 system.

• Carbonic acid is not fully neutralized until a pH of 8.2 and will not depress pH below 4.5.

• CO2 acidity is in the pH range of 8.2 to 4.5 , mineral acidity due to industrial waste is below pH 4.5. 

Salinity Content• Salinity is a measure of content of salts in soil or water.

• Saline water is used in the dyeing process, when saline water, cloth and dye are placed in the dyeing machine. The salt dissolved in water drives the dye out of the water and in to the cloth.

• The cloth is then removed and water containing the dissolved salt is left behind. Total Dissolved Solids (TDS)• TDS comprise of inorganic salts and small amounts of organic matter that

is dissolve in water. The TDS is measured in ppm (mg/ltr).

• TDS affects quality and efficiency in many processes from boiler water to the dye house.

• A TDS reading of 65-150 ppm is considered appropriate for the dye house.

Total Suspended Solids (TSS)• The suspended solids are discrete particles which are insoluble in

water .

• These can be removed by filtration and are also measured in ppm.

Specific Conductivity• Specific conductivity is the ability of water to conduct electricity.

• Conductivity in water is affected by presence of inorganic dissolved salts such as chloride nitrate etc.

Total Hardness• Hardness is caused by compounds of calcium and magnesium, and a

variety of other metals.

Types of Hardness:

• Temporary Hardness: When only bicarbonate salts of Ca and Mg are present.

• Permanent Hardness: When sulphate chloride and nitrate salts of Ca and Mg are present.

Iron Content• Iron can occur in water in a number of forms.

• Water turns red or brown due to presence of ferrous iron called as clear-water iron.

• Water turns red or yellow due to presence of ferric iron called as red-water iron.

• So we should take care that there should be minimum iron content in the water used for textile wet processing.

Desirable Water Quality Parameters for Textile Wet Processing• pH →6.5-7.5

• TDS → 300 ppm

• Color → 5 Hazen No.

• Total Hardness → 30 ppm

• Turbidity → nil

• Suspended Solids → nil

• Copper →0.01 ppm

• Manganese → 0.05 ppm

• Aluminium → 0.2 ppm

• Chloride →150 ppm

• Sulphate →150 ppm

• Nitrate → nil

• Iron →0.01 ppm

• Chromium →0.01 ppm

Disadvantages of Hard or Unsuitable water usage in textile processing• Formation of hard soaps with calcium and magnesium ions, which

results into shade change.

• Carbonates of calcium and magnesium precipitate iron and aluminum mordant and substantive cotton dyestuffs.

• Some dyes got duller and even scum formation happens in the hard water.

• The metal ion impurities such as iron and copper , is a problem in the peroxide bleaching baths, iron is responsible for reducing the brightness of many dyes and is also objectionable in the washing off operations.

• Hard water is responsible for scale formation in the boilers.

• If temporary hardness is high, the soft scales are formed which causes corrosion.

Cont…• In desizing process hard water deactivate enzymes and insolubilize

size materials such as starch, PVA etc.

Conclusion• Water is used extensively throughout the textile processing

operations.

• Almost all dyes, especially chemicals and finishing chemicals are applied to textile substrates from water baths.

• It is mandatory to ensure that the quality of water is met according to the set standards for the dye house.

Method of reducing water consumption• Bio-scouring method

• Solvent Dyeing

• Air dyeing

• Enzyme Dyeing

• Compressed & pressurized CO2 Dyeing

How to minimize cost of water? • Substitutions of dyeing machines using low liquor ratio, equipment

able to substantially reduce bath ratio and allow considerable saving of energy, water & dyes.

• Optimization of process conditions such as temperature and time.

• Combining operation of scouring and bleaching.

• Introducing automatic computer controlled dyeing system, dosing system, dye machine controllers of parameters.

• Process water reuse and recycling.