Chemical Characteristics of water

• Acidity

• Alkalinity

• Hardness

• Turbidity

Acidity:

Acidity or alkalinity is measured by pH. PH measures the concentration of Hydrogen ions in water. Ionization of water is

HOH H+ + OH-

In neutral solutions [OH] = [H] hence pH = 7

If acidity is increased, [H] increases and pH reduces from 7 (because H is log of [H]). The value of pH of water is important in the operations of many water and waste water treatment processes and in the control of corrosion.

Alkalinity:

The values of pH higher than 7, shows alkalinity. The alkaline species in water can neutralize acids. The major constituents of alkalinity (or causticity) are OH-, CO32- and bicarbonates HCO3 ions. Alkalinity in water is usually caused by bicarbonate ions.

Hardness of water: Definition of hard water

Hardness is the property that makes water to require more soap to produce a foam or lather. Hardness of water is not harmful for human health but can be precipitated by heating so can produce damaging effects in boilers, hot pipes etc by depositing the material and reducing the water storage and carriage capacity.

Absolute soft water on the other hand is not acceptable for humans because it may cause ailments, especially to heart patients.
Hardness in water is commonly classified in terms of the amount of CaCO3 (Calcium Carbonate) in it.

Table 1 - Degree of Hardness

Low level of hardness can be removed just by boiling but high degree of hardness can be removed by addition of lime. This method has also the benefit that iron and manganese contents are removed and suspended particles including micro-organisms are reduced.