01-Uses of Water

8/10/2019 01-Uses of Water

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USES OF WATER


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USES OF WATER

Domestic use

Civic use

Trade or business useCommercial or industrial use

Various uses of water:


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DOMESTIC USE

Should possess high degree of purity

Free from suspended impurities, bacteria etc.

Small degree of hardness is permissible


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DOMESTIC USE

Pure, potable or wholesome water should be:

Colourless, odourless and clear

Free from suspended, soluble and colloidal impurities

Free from sediments

Fresh and tasty

Free from harmful organisms

Free from radioactive substances

Free from hardness

Free from poisonous and corrosive substances


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CIVIC USE

Washing roads, cleaning sewers etc.

Large quantity of water required

Certain degree of impurity can be tolerated Water containing suspended and dissolved

impurities may be permitted


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TRADE OR BUSINESS USE

Depends on nature of trade

Laundry- clear, soft and free from iron

Stables may contain impurities

Artificial silk clear, bright and free from colour

Concrete clean and free from sulphates and

chlorides

Dairies bacterial purity


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COMMERCIAL OR INDUSTRIAL USE

Should be chemically pure

Chemical processes involved in production

Slight amount of impurity may affect finalresults of the product

Factories install own water supply plant to suit

their needs


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ANALYSIS OF WATER


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Analysis of water

Physical tests

Colour

Taste and odour Temperature

Turbidity

Chemical tests

Chlorides

Dissolved gases Hardness

pH value

Metals andother chemical

substances

Nitrogen &compounds

Total solids

Bacteriological

tests

Total count oragar platecount test

B-coli test


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PHYSICAL TESTS

Colour

Measurement of colour in water is carried out by

means of a TINTOMETER

The unit of colour on cobalt scale is the colour

produced by one milligram of platinum cobalt in 1

litre of distilled water

For public water supply, the number on cobaltscale should not exceed 20 and should be

preferably less than 10


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PHYSICAL TESTS

Taste and odour

Test is carried out by inhaling through two tubes

of an OSMOSCOPE

May also be tested by threshold number

Water to be supplied from a public water supply

scheme should not contain objectionable taste

and odour Odour is expressed as disagreeable, earthy, fishy,

grassy, mouldy etc.

Taste brackish, saline, salty etc


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PHYSICAL TESTS

Temperature

Desirable temperature of potable water is 10C

while temperature above 25C is considered to be

objectionable

Used to indicate density, viscosity, vapour

pressure, surface tension etc.

Determines saturation values for solids and gaseswhich need to be dissolved

Rates of chemical, biochemical and biological

activity


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PHYSICAL TESTS

Turbidity

Colloidal matter present in water imparts turbidity

Expressed in terms of parts of suspended matter

per million parts of water (p.p.m)

P.p.m is equivalent to mg per litre

Permissible turbidity of drinking water is 5 to 10

p.p.m Measurement is done by a TURBIDITY ROD or

TURBIDIMETER


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CHEMICAL TESTS

Hardness Temporary hardness due to presence of bicarbonates

of calcium and magnesium - Can be removed byboiling or by adding lime to water

Permanent hardness due to presence of sulphates,chlorides and nitrates of calcium and magnesium -removal is through a process called water softening

Hardness is expressed in terms of degree of hardness

approx. 14.3 mg of CaCO3 in a litre of water Water having a hardness of 5 degrees is reasonably

soft, and for potable water, hardness shouldpreferably be more than 5 and less than 8 degrees


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CHEMICAL TESTS

Hydrogen ion concentration (pH value)

Acidity or alkalinity of water is measured in termsof its pH value or H-ion concentration

Water becomes acidic when positively charged Hions are in excess than negatively charged OHions, and alkaline other way round

Neutral water has pH of 7

As water becomes acidic, pH value decreases Two methods electrometric and colourimetric

method


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BACTERIOLOGICAL TESTS

Examination of water for presence of bacteria

Detected by circumstantial evidences or

chemical reactions

Bacteria maybe harmful (pathogenic) or

harmless (non-pathogenic) to humans

Practically all natural waters contain some

variety of bacteria

Affected by air, soil, vegetation, life forms etc.


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WATER TREATMENT


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WATER TREATMENT

Sedimentation

Coagulation and flocculation

Filtration Disinfection Chlorination, ozone treatment,

ultra-violet radiation etc.

Additional treatment

Membrane filtration,water softening, aeration, desalination,

carbon adsorption etc.


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SEDIMENTATION

Sedimentation tanks orclarifiers removeinorganic impurities

Designed to give

complete rest or reducethe flow velocity

Heavier inorganicimpurities settle at thebottom and lighter

impurities float at thetop.

Both can be removed


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COAGULATION AND FLOCCULATION

Chemicals (coagulants)

are added to the water

to bring the non settling

particles together intolarger, heavier masses

of solids called floc

Common coagulants

Aluminium sulphate

Magnesium carbonate

Sodium aluminate


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FILTRATION

The most common type of filter is a rapid sand

filter

Water is passed through thick layer of sand

Membrane filters are widely used for filtering

both drinking water and sewage.


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DISINFECTION

Chlorination

The addition of chlorine or chlorine compounds asdisinfecting material

High solubilty Readily available as gas, liquid or powder

Toxic to micro-organisms

Long lasting effects

Cheap and reliable Direct application of gaseous chlorine from

pressurized steel containers - most economicalmethod for large volumes of water


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DISINFECTION

Ozone

Since ozone is unstable, it cannot be stored and

must be produced on-site, making the process

more expensive than chlorination

Advantages: do not cause taste or odour

problems; it leaves no residual in the disinfected

water


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DISINFECTION

Ultraviolet radiation

Destroys pathogens, and its use as a disinfecting

agent eliminates the need to handle chemicals.

It leaves no residual, and it does not cause taste or

odour problems.

High cost of its application makes it a poor

competitor with either chlorine or ozone as adisinfectant.


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REFERENCES:

Hammer, Hammer Jr. (2011). Water and Waste Water Technology. PHI Learning Private

Limited.

Rangwala, S.C. (1998). Fundamentals of Water Supply and Sanitary Engineering. Charotar

Publishing Company, Anand.

Panchdhari, A.C. (1993). Water Supply and Sanitary Installations. Wiley Eastern Limited.

www.eoearth.org/article/water_resources

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01-Uses of Water