VPE 511: Environment and Environmental Hygiene (2+1)

Estimation of total hardness of water

EXERCISE-5: ESTIMATION OF TOTAL HARDNESS OF WATER

Introduction

• Water hardness is a measure of the capacity of water to react with soap. Hard water requires considerably more soap to produce lather.
• Hardness is contributed by a variety of polyvalent metallic ions mainly carbonates and sulphates of calcium and magnesium.
• Other salts of iron, manganese, zinc, etc. may also contribute to hardness. Hardness is most commonly expressed as mg / litre of CaCO 3 equivalent

Source

• Ployvalent metallic ions are contributed by rocks and seepage or run offs from soils.
• The sources of calcium and magnesium are sedimentary rocks, limestone and chalk.

mg / L of CaCO3 equivalent	Description of water
0-17	soft water
17-60	slightly hard
60-120	Moderately hard
120-180	Hard water
>180	very hard