Question

What is the most important aim in treating water for drinking purposes? Which is more important in treating drinking water: (i) to remove colour so that the water is clear or (ii) to disinfect the water? Explain. What risks occur when chlorine is used to disinfect water that has dissolved organic matter present in the treated water. With coagulation and flocculation, are all organic compounds removed from drinking water? Explain briefly

Answer 1

The most important aim in treating water for drinking purposes is to remove the contaminants from raw water to make it pure for the human consumption without any threat to health. It involves processes such as settling, filtration disinfection, coagulation and flocculation.

In treating drinking water disinfection of water is more important than removal of colour of water. Because disinfection leads to removal, deactivation or killing of pathogenic microorganism present in water which can be a threat to human health. On the other hand, colour by itself is not a toxic one and doesn't cause health concerns. So removal of pathogenic microorganism is much more important than removal of water.

Chlorine is one of the most widely used disinfectant. But with water having organic matters, chlorine can form a number of organic compounds, some of which are a concern for human health. Moreover, chlorine can effect respirational system and also can causes skin and eye irritation. But one can make effective disinfection with chlorine by making use of small amount of chlorine.

The coagulation-flocculation processes facilitate the removal of colloidal particles and is depends upon some factors - velocity gradient, the time and the pH . All these factors will determine the effective removal of the organic compounds present in the drinking water.