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Chapter: Environmental Engineering - Quality of water

Palatability and Impurities in water

To be palatable, water must be significantly free from colour, turbidly, taste and Adour and of moderate temperature in summer and winter and well aerated. At least 4 human perceptions respond to these qualities.

PALATABILITY

 

To be palatable, water must be significantly free from colour, turbidly, taste and Adour and of moderate temperature in summer and winter and well aerated. At least 4 human perceptions respond to these qualities.

 

 

 

IMPURITIES IN WATER

 

Impurities in water may be organic, inorganic and living organisms. Both organic and inorganic impurities may be in the form of suspended, colloidal, sett liable and dissolved state.

 

 

 

SUSPENDED IMPURITIES includes silt, clay, Algae, Tung, organic and inorganic matters and mineral matters etc…. They neither settle down nor dissolve in water and are microscopic and make water turbid. Bacteria cause diseases while silts, clay, Algae, protozoan?s cause turbidity, odor and colour in water. The concentration of suspended matter in water is measured by turbidity.

 

COLLOIDAL IMPURITIES

 

Colloids are particles in a finely divided state. They are neither in suspension nor insolvable but in condition midway between the two. These particles are so small that their removal in a sedimentation tank is impossible at reasonable overflow rates and detention time. They are not visible to the naked eye and are electrically charged and repel cash other. The size of these particles is between 1 minor to 1 mille micron. They impart colour to the water.

 

 

 

DISSOLVED IMPURITIES

 

Their numbers may be very large because water is a very good solvent and can dissolve all the salts to which it comes in contact. Salts of calcium, magnesium when dissolved in water cause taste, hardness, alkalinity, etc….

 

1.IMPURITIES

A)INORGANIC

a. Suspended

b.Dissolved

 

CAUSES             

Particles of silt and clay

I)Carbonates  and bicarbonates of calcium and mg.               

ii)Sulphates  and  chortles  of  ca and mg.           

iii)carbonates  and         bicarbonates of sodium          

iv)Nitiates                               

v)chlorides of Na

vi)Fluorides of Na                  

vii)Iron oxide                

viii)Manganese              

                  

EFFECTS           

Turbidity             

Hardness & alkalinity   

Hardness and corrosion

Alkalinity            

Excess        over   50mg/lit

Methenoglubanemiao r blue babies. Brackish taste                

Excess over 1.5mg/L causes Fluor sis.                

Taste colour and hardness      

Taste and odour  

 

 

 

2.IMPURITIES

B) ORGANIC

I. Suspended

a.vegetable

b.animal

II.Dissolved

a.vegetable

b.Animal

 

CAUSES   

Decayed      leaves,

algae,Fungi,etc..  

Dead  animals,  hairs,    insects, etc..         

Large Quantities   of albuminoidal   nitrogen       with little    quantities  of  ammonia and chlorides.   

Large quantities    of Albuminoidal nitrogen       

 

EFFECTS

Acidity, taste and colour Contamination

Bacteria.

Pathogens, contamination due to sewage. Etc…

 

WATER  BACTERIA

 

May bacterias are found in water most of them are of no sanitary significance. Few in numbers are pathogenic. These include bacteria causing typhoid fever, Para typhoid, Dysentery,

 

Gastro enteric diseases, etc…

Water bacteria may be classified in 4 ways.

 

1)    According to Oxygen Demand

 

a.     Aerobic bacteria = those which require light and free oxygen for their living and development.

 

b.     Anaerobic bacteria = those which do not require light and free oxygen for their living and development.

 

c.      Facultative bacteria = those which can exist in presence or absence or light and free oxygen. They grow more in absence of oxygen.

 

2)    According to Shape

a.     Cocci bacteria = Cells are round or spherical.

b.     Bacilli = Cells are rod shaped.

c.      Spirilla = Spiral shaped cells.

 

3)    According to their diseases producing characteristics

 

a.     Pathogenic bacteria = those which are harmful to human life. They causes diseases like typhoid, Dysentery, cholera, etc…

 

b.     Non-pathogenic bacteria = those do not cause diseases to human.

 

4)    According to the Temperature Flourish

a.     Psycryophilic bacteria = which can persist at low temperature only Range 10 - 200C.

b.     Mesophillic = which can thieve within the temperature range of 200C to 400C.

c.      Thermophillic = It is most effective in the temperature range of 40-650C.

 

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