Chap 5. Water Quality.pptx

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INTRODUCTION TO WATER SUPPLY
ENGINEERING

INTRODUCTION TO WATER SUPPLY
CHAPTER THREE
WATER QUALITY

Water Quality
Introduction;
 Absolutely pure water is never found in nature and contains number
of impurities in varying amounts. The rainwater which is originally
pure also absorbs various gases, dust and other impurities while
falling.
 This water when moves on the ground further carries salt, organic
and inorganic impurities. So this water before supplying to the public
should be treated and purified for the safety of public health, and
economy.
 It is most essential for the water work engineer to check, analyze and3

Water Quality
Characteristics of Water;
 To describe the characteristics of water we will use the following three parameters;
1. Physical Characteristics; Physical parameters define those characteristics of water
that respond to the senses of sight, touch, taste or smell. E.g. turbidity, color, taste, odor,
and temperature etc.
2. Chemical Characteristics; This include Total solids, alkalinity, PH, hardness,
fluorides, metals, organics, and nutrients which are chemical parameters of concern in
water-quality management
3. Biological Characteristics; The presence or absence of living organisms in water can
be one of the most useful indicators of the quality of water.
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Physical Characteristics
 Physical characteristics include:
1. Turbidity
2. Color
3. Taste and odor
4. Temperature,
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1. Turbidity;
 Turbidity is a measure of resistance of water to the passage of light through it. Turbidity is
expressed as NTU (Nephelometric Turbidity Units) or PPM (parts per million) or Milligrams
per liter (mg/l) . Drinking water should not have turbidity more than 10 NTU.
 It is generally cause by silt, clay rock fragments, and metal oxides and it may impart
color of water to brown.
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 Color; Pure water is colorless, but water in nature is often colored by foreign
substances. Colored water is not aesthetically acceptable to the general public.
 Highly colored water is unsuitable for laundering, dyeing, papermaking, beverage
manufacturing, diary production and other food processing, and textile and plastic
production.
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2. Odor and Taste;
 Many substances with which water comes into contact in nature or during
human use may import perceptible taste and odor. These include
minerals, metals, and salts from the soil, and products from biological
reactions, and constituents of wastewater.
 Consumers find taste and odor aesthetically displeasing. Because water is
thought of as tasteless and odorless, the consumer associates taste and
odor with contamination and may prefer to use a tasteless, odorless water
that might actually pose more of a health threat.
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3. Temperature;
 temperature is one of the most important parameters in
natural surface-water systems.
 Temperature increase may affect the portability of water,
and temperature above 15 c is objectionable to drinking
water.
 The temperature of surface waters governs to a large
extent the biological species present and their rates of
activity. 9

Chemical Characteristics
1. Total Dissolved Solids (TDS)
2. Alkalinity
3. PH
4. Hardness
5. Major ions
6. Minor or trace Elements
7. Salinity
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1. Total Dissolved Solids (TDS)
 Total Solids is the term applied to the material residue left in the vessel after
evaporation of a sample and its later drying in an oven at a defined temperature. Total
solids include the Total Suspended Solids (TSS) and Total dissolved solids (TDS).
 Total Suspended Solids (TSS) are the amount of filterable solids in a water sample.
The filters are dried and weighed to determine the amount of total suspended solids in
mg/l of sample
 Total Dissolved Solids (TDS) are those solids that pass through the filter with a pore
size of 2µm or smaller. After filtration the filtrate (liquid) is dried at 103-105 °C and
the remaining residue is weighted and calculated as m/l of TDS.
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2. Alkalinity;
 Alkalinity is thus a measure of the ability of water to neutralize acids.
 Alkalinity may be caused by dissolved strong bases such as NaOH or KOH
(and other hydroxide containing compounds), and it may also be caused by
dissolved carbonates, bicarbonates, and phosphates.
 In large quantities, alkalinity imparts a bitter taste to water or Non pleasant
taste.
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3. pH;
 pH is a measure of the concentration of free hydrogen ion in
water.
 The values of pH 0 to a little less than 7 are termed as acidic and
the values of pH a little above 7 to 14 are termed as basic or
alkaline. When the concentration of H+ and OH- ions are equal
then it is termed as neutral pH.
 pH is measured by pH meter. Pure water is only weakly ionized.
 pH is important in the control of a number of water treatment and
waste treatment processes and in control of corrosion
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4. Hardness;
 Hardness is caused by alkali earth elements mainly Calcium and Magnesium.
 Two types of hardness can be identified- carbonate and non-carbonate hardness.
Carbonate hardness is sometimes called temporary hardness because it can be removed by
boiling water. Non-carbonate hardness cannot be broken down by boiling the water, so it
is also known as permanent hardness
 Methods of removal of hardness
1. Boiling
2. Lime addition
3. Lime soda process
4. Base exchange or Ion exchange
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5. Fluoride;
 fluoride is toxic to humans and other animals in large quantities, while small concentrations
can be beneficial. Concentrations of approximately 1.0 mg/L
 If the fluoride concentrations in water exceed 2.0 mg/L, it can result in discoloration of teeth,
called mottling. Concentrations which exceed 5 mg/L can also result in bone fluorosis and other
skeletal abnormalities.
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6. Organics;
 Dissolved organics in water are usually divided into two broad categories:
Biodegradable and Non-biodegradable.
 Biodegradable; this materials usually consist of fats, proteins, alcohols, acids, and
aldehydes.
 Non-biodegradable Organics; the common organic materials in natural water systems
which are resistant to biological degradation include lignic acids and cellulose.
 And the amount of oxygen consumed during microbial utilization of organics is called the
biological oxygen demand (BOD). 16

 The Biological Oxygen Demand (BOD) is measured by determining the oxygen consumed
from a sample placed in an air-tight container and kept in a controlled environment for a
preselected period of time.
 In the standard test, a 300 mL BOD bottle is used and the sample is incubated at 20oC for
5 days. Light must be excluded from the incubator to prevent algal growth that may produce
oxygen in the bottle.
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Biological Characteristics of Water
 Pathogens; Pathogens are organisms capable of infecting, or of transmitting diseases to
humans. These organisms are not native to aquatic systems and usually require an
animal host for growth and reproduction. These, waterborne pathogens, include
species of bacteria, viruses, protozoa, and helminthes (parasitic worms).
 Bacteria:. Cholera and typhoid are the most violent of waterborne bacterial diseases.
 Viruses: main cause of Rotaviruses, Hepatitis A and E, and Polio.
 Protozoa: mainly cause of Malaria.
 Helminthes; are main cause of Guinea Worm
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Testing for Pathogens
 Coliforms
 The most important biological indicator of water quality and pollution used in public
health technology is the group of bacteria called coliforms. The most famous been
Escherichia coli or (E. Coli).
 E. Coli are nonpathogenic common inhabitants of the intestinal tract, they are also,
common in the soil, on leaves, and on grain. The test for these microorganisms, is called
Total Coliform Test,
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Figure 3; Testing for Pathogens Using E-Cole.
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Figure 4; E-Cole Testing in Water
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Waterborne Diseases
 Water-related disease organisms have been classified as:
 Waterborne: pathogens that originate in fecal material and are transmitted by
drinking water.
 Water-washed: organisms that originate in feces and are transmitted through
contact because of inadequate sanitation or hygiene.
 Water-based: organisms that spend part of their life cycle in aquatic animals and
come in direct contact with humans in water, often through; the skin (Guinea
Worm)
 Water-related (Vector Born Diseases): microorganisms with life cycles
associated with insects that live or breed in water and bite susceptible
individuals. 22

Fecal oral transmission routes (F-Diagram)
Figure 5; F-Diagram
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Fecal oral transmission routes (F-Diagram)
Figure 6; F-Diagram with Barriers
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Chap 5. Water Quality.pptx

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Chap 5. Water Quality.pptx