Factors contributing to water pollution

1. FACTORS CONTRIBUTING
TO WATER POLLUTION
Tharakeswari S

2. Evocation

3. Contents
COTTON TEXTILE PROCESSING EFFLUENTS
 Flow chart of cotton processing
 Characteristics of cotton textile processing effluents.

4. Cotton flow chart

5. DESIZING
DESIZING
ACID
DIL ACIDS
HCl &
SULPHURIC
ENZYME
AMYLASE
In case of synthetic enzymes like PVA and CMC, desizing is
done using detergent as they are readily soluble in water.

6. SCOURING
 Kiering
 The kiering process consists of boiling the cloth to remove grease, waxes,
natural fats and other impurities by an alkaline solution containing 1 to 3
percent of caustic soda, soda ash and other chemicals for several hours with the
aid of steam.
 The process is carried out either on a batch basis as in some of the older mills
or on continuous basis in special units like J boxes in the modern mills.
 The spent liquor is blown out followed by washing of the cloth with a large
volume of water.

7. BLEACHING
 The fabric from the kiers subsequently under-goes bleaching with alkaline
hypochlorite solution or chlorine or peroxide (hydrogen peroxide is used for
bleaching of delicate fabrics), I
 n peroxide bleaching, sodium peroxide, sulphuric acid, caustic soda and a
soluble oil are used. Sometimes peroxide bleaching is carried out directly in the
kier itself or as a second stage after the kier.
 The bleaching operation is followed by a wash with plain water and then by
souring (acid and sodium bisulphite) to remove the last traces of alkali and
chlorine.
 The fabric is then soaped and treated with ultramarine blue to improve its
whiteness.

8. MERCERIZATION
 The process consists of treating cloth with a cold concentrated solution of
caustic soda (200 g/l) and then washing with profuse quantities of water by a
counter-current system.
 The strong caustic is reused.
 The fabric is then treated with a diluted acid solution to remove the last traces
of alkali, followed by a second rinse with fresh water.
 Mercerization improves the strength elasticity, lustre and affinity for colours.

9. DYEING
 Dyeing— The dyeing of cloth is carried out with a variety of dyes and dyeing processes
which are briefly described below:
 Direct dyes—These are neutral substances and are applied to the fabric without any
mordants. These are easy to apply, fairly fast to light and are stable for washing.
 Basic dyes—Theses are neutral substances of colour base and are applied with an acid,
like, tannic acid, as mordant followed by a solution of tartar emetic. These dyes are
noted for their bright colours.
 Vat dyes—Vat dyes belong to the class of fast dyes which are insoluble in water but are
applied with the aid of powerful reducing agents such as sodium hydrosulphite and
alkali. The cloth is then exposed to oxidation by air or oxidizing agents followed by
souring to neutralise the excess of alkali. The fabric is washed at the end of each
operation.7

10. DYEING
 Sulphur dyes—These contain sulphur compounds and are applied along with a
reducing agent like sodium sulphide followed by oxidation.
 Naphthol dyes—The colour is developed on the fibre by a two stage process
consisting of (1) treatment with betanaphthol and (2) diazotization. This is
followed by hot soap and caustic soda.

11. PRINTING
PRINTING
 Printing of cotton textiles is carried out either by means of hand block printing or
roller printing in machines.
 Different techniques are employed, depending upon the dye used.
 The colour is applied as a thick paste along with starch or gum and mordant.

12. CHARACTERISTICS OF COTTON PROCESSING
EFFLUENTS
 Desizing Wastes
 consist of mostly of washings and contain colloidal and dissolved organic
matter derived from the hydrolysis of starch by enzymes.
 The waste volume is small but has a high BOD which amounts to 35 to 50
percent of the total BOD.
 Kier Wastes
 The spent kier liquor and the washings are dark brown in colour and are
strongly alkaline.
 They contain caustic soda and suspended solids most of which are fragments of
cotton.
 The wastes have high pH, total dissolved solids, alkalinity and BOD.
 The BOD of the kier liquor is about 30 to 35 percent of the total waste load.

13. (Contd…)
 Bleaching and Mercerizing Wastes
 These are small in volume but highly alkaline.
 The wastes contain organic matter and the chemicals used such as hypochlorite,
chlorine, caustic soda and peroxide.
 The BOD load contributed by the wastes from bleach house is about 5 percent.
 Dyeing Wastes
 The dyeing process contributes a large volume of waste water.
 Its composition and characteristics are highly variable and exert a high oxygen
demand due to the organic matter of the dyes, reducing agents like sulphide,
hydrosulphite, nitrite, acetic acid and soaps.
 The BOD contribution from the dye house is about six percent of the total mill
waste.

14. (Contd…)
 Printing Wastes
 The waste water derived from the printing process consists of colours, starch,
gum and oil used in making the pastes and soaps.
 The quantity of the waste streams is small but has a fairly high BOD and
chemical oxygen demand (COD).
 Finishing Wastes
 The finishing of the cotton fabrics contributes a negligibly small volume of
waste water containing traces of starch, tallow and salts, etc.

15. ANALYSIS OF PROCESS WASTE WATERS OF COTTON
TEXTILE MILLS
T No. Characteristic Desizing Kiering Bleaching Mercerizing Dyeing Printing
1 pH value 8.6 to 10.0 10.9 to 11.8 8.4 to 10.9 8.1 to 9.8 9.2 to 11.0 6.7 to 8.2
2 Alkalinity, mg/l 490 to 2480 4 740 to 19000 2 780 to 6 280 930 to 1 005 1 250 to 3 160 500 to 1 080
3 Total solids, mg/l 7 870 to 8920 14 220 to 40580 2 980 to 8 240 2220 to 3 030 3 600 to 6 540 2 120 to 2 750
4 Total dissolved solids,
mg/l
5 580 to 6 250 12 260 to 38500 2 780 to 7 900 2 060 to 2 600 3 230 to 6 180 1 870 to 2 360
5 Suspended solids, mg/l 2 290 to 2670 1960 to 2080 200 to 340 160 to 430 360 to 370 250 to 390
6 Biochemical oxygen
demand (5 days at
20°C), mg/l
1 000 to 1080 2 500 to 3480 875 to 535 100 to 1 222 130 to 820 135 to 1 380
7 Chemical oxygen
demand, mg/l
1 650 to 1750 12 800 to 19600 1 350 to 1 575 246 to 381 465 to 1 400 410 to 4270

16. CHEMICAL CHARACTERISTICS OF COMBINED
WASTES OF INTEGRATED COTTON TEXTILE MILLS
Sl No. Characteristic Cotton Textile Mill
Range Mean
1 pH value 6.7 to 11.8 –
2 Total alkalinity (as CaCO3), mg/l 296 to 1 098 721
3 Total dissolved solids, mg/l 1 200 to 4 438 2 470
4 Suspended solids, mg/l 80 to 1 732 380
5 Biochemical oxygen demand, (5 days at
20°C), mg/l
65 to 760 235
6 Chemical oxygen demand, mg/l 358 to 1 418 650
7 Chloride (as Cl), mg/l 350 to 1 390 550
8 Sulphate (as SO4), mg/l 70 to 600 280
9 Calcium (as Ca), mg/l 0 to 68 24
10 Magnesium (as mg), mg/l 6 to 58 28
11 Sodium (as Na), mg/l 520 to 2 350 956
12 Potassium (as K), mg/l 3 to 69 21.5
13 Percent sodium 79 to 97.5 90

17. IMPORTANT PARAMETERS

18. MIND MAP

19. Synthetic Processing
 Man made polymers are derived from pure chemical compounds
 Light scouring or bleaching are enough to prepare the cloth for dyeing and
subsequent processes.
 Prominent synthetic fibers – Rayon, Acetate, Nylon, Acrylic, Polyester etc.
 The major pollutants released during synthetic fibre processing operations are
 Oil
 Synthetic Detergent
 Dye
 Antistatic lubricants
 Softeners
 Sizes like PVA, CMC etc.
 Bleach – Hydrogen peroxide, sodium nitrite, Preacetic acid etc.
 Finishing - softeners, NaOH, etc.

20. CHEMICAL CHARACTERISTICS OF COMBINED WASTES OF
INTEGRATED SYNTHETIC TEXTILE MILLS
Sl No. Characteristic Synthetic Textile Mill
Range Mean
1 pH value 7.3 to 8.0 –
2 Total alkalinity (as CaCO3), mg/l 550 to 630 590
3 Total dissolved solids, mg/l 1 060 to 1 080 1070
4 Suspended solids, mg/l 80 to 130 100
5 Biochemical oxygen demand, (5 days at 20°C),
mg/l
180 to 200 190
6 Chemical oxygen demand, mg/l 420 to 630 525
7 Chloride (as Cl), mg/l 130 to 205 170
8 Sulphate (as SO4), mg/l 50 to 90 65
9 Calcium (as Ca), mg/l 14 to 17 15
10 Magnesium (as mg), mg/l 17 to 22 19
11 Sodium (as Na), mg/l 830 to 1 050 900
12 Potassium (as K), mg/l 8 to 10 9
13 Percent sodium 92.5 to 94.5 93

21. Contd…
Parameters Standard effluent Synthetic
pH 5.5 - 9 7 -9
BOD 30 – 350 ppm 150 – 200 ppm
COD 100- 250 ppm 400 – 650 ppm
TDS 1500 – 2100 ppm 1060 – 1120 ppm
The effluent characteristics form synthetic processing industry.

22. Evocation

23. Wool Processing
 Wool processing involves numerous operations most of which are mechanical and
dry operations.
 Scouring
 Scouring under various stages to remove natural and acquired impurities
followed by rinsing.
 Scouring of wool produces three waste streams namely desuinting effluent, the
scour liquor and the rinse water.
 The scour liquor is highly oily, alkaline and turbid brown colour liquid.
 The BOD, COD, suspended solids and grease content are extremely high.

24. Contd…
 Weaving
 stock dyeing, carding, oiling (to remove static electricity), roving, spinning and
weaving.
 Mills that carry out only weaving and finishing operations would produce a
composite waste with much lower concentrations of BOD, suspended solids
and grease than scouring effluents.
 Among the finishing operations wool dyeing is the major source of colour and
contributes to significant levels of BOD
 Finishing
 Fulling (imparts a felt quality to the wool),
 Carbonizing (to remove the residual vegetable matter and other impurities),
 Piece dyeing (if stock dyeing is not carried out) and
 Bleaching/brightening.

25. Contd…
Parameters Standard effluent Wool
pH 5.5- 9 3 - 10
BOD 30 -350 ppm 5000 – 8000 ppm
COD 100 -250 ppm 10000 – 20000 ppm
TDS 1500 – 2100 ppm 10000 – 15000 ppm
The effluent characteristics form woolen processing industry.