Mayurbhanj School of Engineering

Science & Humanities Dept.

WATER TREATMENT

Presented by- Miss Mamata Mohanta

Lect. in chemistry

M.S.E

SOFT WATER

Soft water is surface water that contains low concentrations of ions and in particular is low in ions of calcium and magnesium. Soft water naturally occurs where rainfall and the drainage basin of rivers are formed of hard, impervious and calcium-poor rocks

HARD WATER

Hard water is water that has high mineral content (in contrast with "soft water"). Hard water is formed when water percolates through deposits of limestone, chalk or gypsum^[1] which are largely made up of calcium and magnesium carbonates, bicarbonates and sulfates. Iron oxides or iron carbonates can give a reddish brown colouration to hard water deposit

The simple definition of water hardness is the amount of dissolved calcium and magnesium in the water. Hard water is high in dissolved minerals, largely calcium and magnesium. You may have felt the effects of hard water, literally, the last time you washed your hands.

TYPES OF HARDNESS

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1. PERMANENT HARDNESS

Permanent hardness is hardness (mineral content) that cannot be removed by boiling. When this is the case, it is usually caused by the presence of calcium sulfate and/or magnesium sulfates in the water, which do not precipitate out as the temperature increases

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2. TEMPORARY HARDNESS

Temporary hardness is a type of water hardness caused by the presence of dissolved bicarbonate minerals (calcium bicarbonate and magnesium bicarbonate). The presence of the metal cations makes the water hard

LIME-SODA PROCESS OF WATER TREATMENT

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Lime soda process: In lime-soda process, hard water is treated with lime (CaO or Ca (OH)₂) firstly, after that with soda. In this process, the hardness is removed by sedimentation as calcium carbonate or magnesium hydroxide. ... The pH should be greater than 9 for sedimentation of the magnesium hydroxide.

It is of 2 types

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1. Cold limesoda process

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2. Hot limesoda process

Organic ion exchange method