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Water & Its treatment Introduction

This chapter deals with

Specification of water,

Hardness of water,

Softening and its treatment.

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Water- Most important and basic requirement on earth

For existence of all living beings

(human, animals, plants)

For industrial processes and agricultural production

Oceans contains- 97% of all the water on earth

Glaciers- 2%

1% available for ready use

Hence it is urgently required to use the available water

most carefully and economically

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Sources of water

1. Rain Water

2. Ground Water Main Sources

3. Surface Water

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Rain Water:

caused due to evap. of surface water &

subsequent precip.

Most purest formDissolves Impurities (SPM, CO2, SO2,

NO2) from atmosphere during pptation

Can be stored in undergroundreservoir tanks

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Ground Water:

Largest available source of fresh water

Form of rain water falling on earth

Generally pure because it undergoes naturalfiltration during the percolation through soil

pores

Less likely to be contaminated by BACTERIA

but contains dissolved salts

To obtain in large quantity tube wells are used

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Surface Water:The water that flows over the surface of earth & is Directly

available

It includes1. River water

2. Lake water

3. Sea water

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River waterComes from melting of snow, rain and spring water

(coming from earth)

Contains dissolved minerals/salts like chlorides,

sulphates, bicarbonates of Na, Ca, Mg

Also contains impurities of sand rocks & organicmatter

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SPECIFICATION OF WATER FOR DIFFERENT USE

Boilers:

Paper Industry:Textile Industry:

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Boilers: Water used in boilers should be

free from hardness because hardwater causes sludge and scale

formation which prevent efficientheat transfer

Dissolved solids may cause causticembrittlement

(material of boiler becomes brittledue to accumulation of causticsubstances)

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Paper Industry:

Should be free from silica and hardness

water increases ash content

Fe & Mn can affect brightness & color of

the paper

Water should be free from alkalinity asalkaline water consume more alum and

increase cost of production.

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Textile Industry:Should be free from hardness as hard water

precipitates basic dyes and decreases the

solubility of acidic dyes

Presence of Fe, Mn salts causes uneven dyes

Should be free from turbidity, colour andorganic matter

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Sugar Industry:

Should be free from sulphates, carbonates

and nitrates otherwise crystallization and

refining of sugar becomes difficult and sugar

obtained is deliquescent (absorb moisture

from air)

Laundries:

Hard water increases consumption of soaps

Cooking:

Hard water increases fuel consumption and

cooking time12

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Dissolved Impurities

Suspended

Colloidal

Microorganism

IMPURITIES IN HARD WATER

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Dissolved Impurities

a) Salts: Carbonates, Bicarbonates, Sulphates and chlorides of Ca,

Mg, Fe, Na, K.

b) Gases: CO2, O2, N2, H2SSuspended impurities

Inorganic-Clay, sand

Organic- Vegetable & animal matter

Colloidal Impurities: Products from organic waste, finely

divided silica and clay etc.

Microorganisms: Bacteria, Fungi, Algae

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End of the lecture

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