Mineral particles may include clay, silt, calcium carbonate and silica. Organic particles may include fine vegetable wastes, fats and microorganisms. Sedimentation in tanks or reservoirs is adequate to clear large particles, but filtration is needed for small or colloidal fragments. Filtration using sand or the use of coagulants followed by filtration may be indicated. The colour in water signals the presence of dissolved or colloidally dispersed organic matter of unknown composition augmented colloidal iron or manganese.
Raw water contains bicarbonates in amounts dependent on their origin.
Often, water may contain small amounts of carbonate alkalines. The number of bicarbonate and carbonate ions present may be isolated by titration using phenolphthalein as an indicator and methyl orange as an indicator in the second stage. Hardness of water. Water hardness is caused by calcium and magnesium salts. Other contributing elements to hardness include metallic ions such as iron and strontium.