Water Analysis -2
The general requirements of the water used in textile processing are given below:
- The water should be colorless, clear and free from suspended impurities.
- Should not be hard and have the tendency to deposit, scale on fabric or on water supply structures
- It should be non-corrosive.
- It should be free from metals such as iron, manganese, aluminums and copper
- It should neither be too alkaline or acidic.
Color is normally an indication of the presence of suspended and dissolved salts that may affect the fiber/yarn/fabric. So it has to be removed from water prior use in processing, by a suitable de-coloration technique.
Turbidity or Suspended solids are due to a fine suspension of inorganic salts like (clay. silica, calcium carbonate) or organic finely divided vegetable matter like algae, micro-organism etc. This should also be removed using a suitable filtration technique.
Dissolved solids - in water treatment and analysis this term is called Total Dissolved Solids (TDS). The TDS reflects the presence of unwanted elements in dissolved form, which has to be removed using a suitable method. Good quality water should not have a TDS more than 150 ppm.
pH value – Water with a pH value of more than 7 is alkaline and one below 7 is acidic. Most of the textile processing treatments are dependent on pH values.
Hardness (Calcium and Magnesium) – the presence of Calcium and Magnesium salts in water is called hardness of water.
Temporary Hardness: The presence of bicarbonates of Calcium and Magnesium in water is called temporary hardness. When the water containing these salts are heated to boil, the soluble bicarbonate salts will become insoluble carbonates and precipitate and the hardness disappears.
Permanent Hardness: The presence of carbonates, sulphates and chlorides of Calcium and Magnesium are called permanent Hardness, as this hardness cannot be removed by simple heating.