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In a textile processing plant, water is a vital raw material not only for the boilers supplying steam for heating and drying purposes, but also for all the wet processes such as scouring, bleaching, dyeing, printing and finishing. The success of these processes largely depends on the quality of the water being used. Generally two qualities of water are to be maintained separately - very pure quality for feeding to the boiler and moderately pure quality for processing purpose.
Sources Of Water
Water with a high degree purity is rarely obtained from natural sources. The mineral constituents differ in amount and relative proportions depending on the source. Supplies of water may be broadly classified into three groups.
Surface Water
It is mainly accumulation of rainwater in streams, rivers and lakes. As it passes over the surface of the earth, it carries organic matters of varying stages of decomposition, a part of which is converted into nitrates by nitrifying bacteria. It also dissolves varius mineral matters, depending on the nature of the soil or rock coming in contact , or may be turbid due to their suspensions. Generally it contains sulphates and chlorides as well as bicarbonates of calcium and magnesium. Decaying vegetables may distinctly discolour surface water.
Subsoil Water
Water, collected from shallow wells or surface springs, is actually surface water percolated a small distance through the soil or rock. It is generally free from suspension as water is being filtered by the passage through soil. It howeve contains dissolved organic matters. Subsoil water is often rich in carbon dioxide arising from metabolism of vegetable life. It converts insoluble calcium carbonayes of rock into water-soluble bicanbonates. The impurity content of subsoil waters may vary significantly.
Deep Well Water
Water from deep wells or deep tube-wells is collected from a considerable depth below the ground and such water has percolated through several layers of ground. Such water is generally free from organic matters due to filtration and bacterial action. The mineral content, however may be very high because of prolonged contact with several layers of rocks and soil. It may contains sodium biacarbonate in addition to the bicarbonates and other salts of calcium, magnesium and iron.
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