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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