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provides Gate-2016 preparation study materials for the candidates seeking for
success. Here the “ENVIRONMENTAL ENGINEERING-Quality of water” topic is explained.
Each and every word given below is important for your civil engineering
competitive examination. And also the GATE-2016 practice sets, Example
problems, previous year Question papers are available in jobghost.blogspot.com.
Quality of Water:
Water is most important for survival
of any living habitants. The drinking water should be in standard and should
not contain any harmful particles. So the water should be treated before
supplying it to the peoples.
The water is tested before and after
treatment to ensure it satisfies the quality of standard potable water. All the
surface and sub-surface water contains impurities. But some are not harmful to
human beings, some causes severe disease to the habitants. So the water is
treated to provide safe potable water to the peoples.
Some definitions of water are given
below.
Pure Water: It is the chemical compound. (H2O)
Potable Water: This is the standard water which is
fit for drinking.
Wholesome water: This is not chemically hundred
percent pure. But will not cause any harm to the habitants. The water which
contains no harmful thing in it is called wholesome water.
Polluted Water: It contains harmful maters which is
unfit for drinking and domestic use.
Contaminated water: The water which contains harmful
pathogenic bacteria is called contaminated water. It is obviously unfit for
drinking.
Mineral Water: It contains most useful minerals such
as Iron, Magnesium, and Calcium in a standard proportion.
Impurities in Water:
Suspended Impurities:
The suspended particle present in the
water is called suspended impurities. Presence of suspended impurities in the
water is called turbid. The common suspended impurities are Silt, clay,
bacteria, fungi and algae. Usually size varies from 10-1 mm to 10-3mm.
Colloidal impurities:
These impurities are fine particle of
soil which usually not visible to the naked eye. These impurities if associated
with organic matter having bacteria become the chief source of the epidemic.
Usually the size of impurities varies from 10-3 mm to 10-6
mm.
Dissolved Impurities:
The organic compounds, inorganic
compounds, inorganic salts and gasses are the most common dissolved impurities.
Size of these impurities varies from 10-6 mm to 10-8 mm. The
effects and impurities are given below.
Metals: Iron causes red colour and
magnesium causes brown colour to the water.
Salts: Salts causes alkalinity and
hardness to the water.
Gases: Oxygen Causes corrosion of
conveying metal pipes.
Chlorine and ammonia cause bad taste and
odour.
Corban-di-Oxide and hydrogen sulphide cause
acidity in water
Note: No impurity is smaller than 10-8
mm
Physical Characteristics of potable
water:
The important physical characteristics of
potable water are pointed below.
i.
Temperature:
As temperature increases Dissolved
oxygen decreases. The less quantity of dissolved oxygen will not satisfy the
potable water standards. And the microorganisms will grow rapidly at high
temperature. Also the high temperature increases the chemical reaction
processes. The lesser temperature will increase the viscosity of water. So the
temperature should be maintained in between 100C to 200
C.
Desirable temperature for potable water=100C
ii.Turbidity:
The presence of suspended particles
such as silt, clay, organic matters and fine particles in the water is called
turbid water. It also caused due to the presence of Bacteria, fungi and
protozoa. So the turbidity is “measure of resistance offered by the suspended
or colloidal particles present in the water to the passage of light”. It is
measured by turbidity meters and measure on “silica scale”.
Jackson Turbidity meter: It is used to measure the high
turbidity in the range of more than 25ppm. Indicated by using JTU (Jackson
turbidity unit).
Baylis turbidity meter: It is used to measure the low
turbidity values in the range of 0 to 2 ppm.
Indicated by using BTU (Baylis Turbidity Unit)
Nephelometer: It is used to measure the turbidity in
the range of 0 to 1 ppm.
The permissible of turbidity in potable water= 5 to 10 ppm.
iii. Colour:
The water is actually colourless. But
the presence of impurities imparts colour to the water. Generally dissolved
organic matters, inorganic colour soils, growth of algae, iron and manganese
causes colour to the water. Apparent colour of water causes due to the presence
of suspended solids. And the true colour is caused by the dissolved solids
present in the water.
Colour is measured by “TINTOMETER” and
expressed in terms of TCU- True Colour Unit.
1 TCU= 1 mg of Platinum in the form of
chloroplatinate ion mixed in 1 liter distilled water.
The decayed vegetation imparts green
or yellow colour, Algae imparts greenish colour, iron Imparts reddish and the
manganese imparts brown or black colour to the water
The permissible limit of Colour in potable water= 5 – 20
TCU
iv.Taste & odour:
Taste and odour is due to the presence
of organic or inorganic salts and dissolved gasses. It is measured by using the
instrument Osmoscope. Taste is expressed in terms of FTN – Flavor Threshold
Number. And The odour is expressed in terms of TON- Threshold Odour Number.
The odour changes with respect to
temperature. So it is normally tested in the temperature of 200 – 25
0C.
The permissible TON in potable water = 1 - 3 TON
v. pH value of water:
This indicates the hydrogen ion
concentration in water.
P
(H+) + P (OH-) = 14
The permissible limit of pH in potable
water= 6.5 to 8
Permissible Limits of important
characteristics are given below…!
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