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.
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.
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.
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….
of silt and clay
I)Carbonates and bicarbonates
of calcium and mg.
chortles of ca and mg.
iii)carbonates and bicarbonates
Excess over 50mg/lit
r blue babies. Brackish taste
over 1.5mg/L causes Fluor sis.
colour and hardness
hairs, insects, etc..
Large Quantities of
albuminoidal nitrogen with little quantities of ammonia and chlorides.
Large quantities of
taste and colour Contamination
contamination due to sewage. Etc…
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
Gastro enteric diseases, etc…
Water bacteria may be classified in
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.
According to Shape
a. Cocci bacteria = Cells are round or
b. Bacilli = Cells are rod shaped.
c. Spirilla = Spiral shaped cells.
According to their diseases producing
a. Pathogenic bacteria = those which
are harmful to human life. They causes diseases like typhoid, Dysentery,
b. Non-pathogenic bacteria = those do
not cause diseases to human.
According to the Temperature
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.