(i)Colour: Yellowish thing indicates the prsence of chromium and appericiable amount of organic matter. Yellowish red colour indicates the presence of iron,while red brown colour indicates the presence of peaty matter.
(ii) Turbidity: It is due to the colloidal ,extermely fine suspension such as clay, slit,finely divided matters(organic and inorganic) micro organisms like plankton etc.
(iii)Taste: It is due to the prsence of dissloved mineral in water produces taste, but not odour.
Bitter taste can be due to the prsence of iron, alumminium, maganese, sulphate or excess of lime.
Soapy taste can be due to the presence of large amount of sodium bi carbonate.
Brackish taste is due to the presence of unusual amount of salts.
Polatable Taste is due to the presence of dissolved gases and minerals like nitrates in water.
(iv) Odour: It is in water due to undesirable for domestic as well as industrial purposes.
Chemical impurities in water:
(i) Acidity: It is not any specific pollutant and it simply determines the power to neutralise hydroxyl ions and is, usually expressed in terms of ppm( or mg/L) of calcium carbonate equivalent.
Surface waters and ground waters attain acidity from industrial wastes like acid, mine, drainage, pickling liquors etc.
(ii) Gases: All natural waters contain dissolved atmosphere Co2. Its solubility depends upon temperature, pressure and dissolved mineral content of water.
On the other hand dissolved oxygen in water is essential to the life of acquatic organisms such as fishes.
Polluted waters and sewages contains nitrogen in the form of nitrogeneous organic compounds and urea, which are partially converted in to NH3.