Friday, November 20, 2009

Water Quality Parameters

Some important parameters of water
:- 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. A Hazen unit is 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 matter 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:- pH is the measure of H+ ions concentration , its value indicates the nature of water ,such as neutral , acidic or alkaline. .pH of less than 7 indicates acidic , neutral at 7 and alkaline when above 7. The pH scale is having value from 0 to 14.
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).
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.
Alkalinity:- 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).
Acidity:- Most natural waters are buffered by a CO2 / HCO3 system. Corbonic 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.
Hardness :-

Water hardness in the water is of two types ,
1.Permanent water hardnessPermanent water hardness is attributed to the presence of sulfates and chlorides of calcium and magnesium. The permanent hardness can only be removed by chemical means .
2.Temporary hardnessTemporary water hardness is attributed to the presence of bicarbonates of calcium and magnesium. The temporary hardness can be removed by boiling the water.

Water hardness is represented in different units :- Mainly it is represented as parts per million as calcium carbonate or mg/lt . other units which are commonly used clark degree, French degree or Russian Degree and German degree.

The carbonate hardness is associated with bicarbonate and non carbonate hardness is associated with chlorides , sulfates , nitrates of magnesium and calcium. The total hardness minus alkalinity is non carbonate hardness.
Other important parameters are
Iron , copper, lead, arsenic, chromium, chlorides, chlorine , fluorides, sulphates and phosphates , DO( dissolved oxygen), nitrogen, nitrites and nitrates, COD ,BOD etc.

Quality parameters of water
for drinking purpose
Characteristic maximum permissible limit in ppm
Arsenic 0.01
Cadmium 0.003
Chromium 0.05
Cyanide 0.05
Fluoride 1.5
Lead 0.01
Mercury 0.001
Nickel 0.02
Nitrate and nitrite Nitrogen 10.0
Nitrite nitrogen 1.0
Selenium 0.01
Chloride 600
Sulphate 400
Hardness as CaCO3 500
TDS (total dissolved solids) 1500
Aluminum 0.2
Copper 1.5
Iron 1.0
Manganese 0.5
Sodium 200
Zinc 15.0
Chlorophenols 0.1 mg/l
DDT 1.0 mg/l
Heptachlor 0.03 mg/l
Lindane 2.0 mg/l
Mono chloro benzene 3.0 mg/l
1,4 dichloro benzene 0.1 mg/l
2,4 D 30 mg/l
Gross alpha activity 0.1 Bq/l
Gross beta activity 1.0 Bq/l(becquerel)
Color 15 TCU( time color unit)
Turbidity 25 NTU (Nephelometric Turbidity Unit)
Taste and Odor Non Objectionable to 90%Consumer.
pH 6.5-9.2
Coliform Absent in any 100 ml sample

Water as a raw material in textile processing

Water is an essential raw material in the industry particularly in the dyeing and processing of textiles. Before selecting a source of raw water dyeing purpose a careful survey of the available water source is well worthwhile.
A good supply of pure water is very important to a bleacher or dyer because a number of faults could be attributed to the use of unsuitable water in the processing of textiles.
With the decreasing availability of a good quality water and ecological concerns , the dyers and bleachers are forced to switch to low water consumption technology as well as to reduce the discharge of polluted water.

Disadvantages of Hard or Unsuitable water usage in textile processing

1. 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.
Desirable Water Quality Parameters for Textile Wet Processing

1.Color 5 Hazen No.
2.pH 6.5-7.5
3.TDS 300 ppm
4.Residue on ignition 250 ppm
5.Total Hardness 30 ppm
6. COD nil
7. Turbidity nil
8.Suspended Solids nil
9.Copper 0.01 ppm
10. Iron 0.01 ppm
11.Chromium 0.01 ppm
12.Manganese 0.05 ppm
13.Aluminium 0.2 ppm
14.Chloride 150 ppm
15.Sulphate 150 ppm
16. Nitrite nil
Water Quality and Treatment
Manual of British water engineering practice. Volume I: Organization & Management. Volume II: Engineering Practice. Volume III: Water Quality & Treatment. THREE VOLUMES
Water Quality and Treatment A Handbook of Public Water Supplies
Water Treatment: Principles and Design
Wastewater Engineering: Treatment and Reuse


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