CHAPTER 5 WATER QUALITY.ppt

Content
 Existing Water supply and Sanitation
Situation in Ethiopia
 H2O Introduction
 Water Quality Characteristic
 Physical Characteristic
 Chemical Characteristic
 Bacteriological Characteristic
 Sanitary Survey
 Drinking water quality Guidelines & Standards
 Water quality phsico-chemical test analysis
format
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Existing water Supply & Sanitation
Situation in Ethiopia
 Low level of safe and adequate water supply access .
 MoWR reports estimate the water supply accesses as
follows:-
 National Water Supply accesses = 61.1%
 Urban Water Supply access = 88.6%
 Rural Water Supply access = 66.2%
 Actual water supply accsse is expected to be lower due to
malfunctioning of about 20-25% of existing water schemes
at any one time.
 The situation of sanitation is less than the water supply.
 MoH reports estimate the National Sanitation Coverage to
be more than 50%.
 Lack of awareness in hygiene and sanitation is critical at all
levels.
3
1/6/2023

Water Quality Situation in
Ethiopia
 The Majority (mainly rural) are without access to
safe and adequate domestic water supply .
 Majority of the population is forced to meet its
needs from unprotected, often contaminated water
sources.
 This in turn implies that the health of the majority
population-is exposed to various types of water
borne/related diseases that are cause for high
mortality and morbidity in the country.
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Water Quality Situation con’t
 The major prevalent/common water quality problems
in Ethiopia are those related to:
 Microbiological : - Total and Faecal
Coliforms.
 Physical : - Turbidity, Colour, Odour
and Taste.
 Chemical parameters :- F- , NO3
-, NO2
-, Fe2+,
Mn2+, Hardness,
SO4
3-, Cl-, pH (alkalinity/
acidity).
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Water Quality Situation con’t
 Possible causes of the major water quality problems are
natural, anthropogenic or both.
 Microbiological pollution of drinking water is recognized as
number one water quality problem in Ethiopia.
 Major water borne diseases in Ethiopia include: diarrhoea,
gastroenteritis, typhoid, bacillary dysentery, cholera, hepatitis, etc.
 Turbidity, colour, odour/smell, and taste are major physical water
quality problem parameters,
 Different pesticides (herbicides, insecticides, fungicides) are
increasingly being applied as a result of growing agricultural
practices.
 No radiological water quality data are available in Ethiopia (lack of
analytical capacity) etc…
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1. H2O Introduction
 Absolutely pure water is never found in nature.
 Absolutely pure water is which contains only two parts H
and one part of O2.
 Water found in nature contains a number of impurities in
varying amounts.
 Rainwater, which is originally pure, also absorbs various
gases, dust and other impurities while falling.
 Water when moves on the ground carries silt, organic and
inorganic impurities.
 Therefore the runoff water has large number of impurities,
which should be treated and purified before supplying to the
public.
 Absolutely purified water is not good for health. Our body
requires certain elements.
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Occurrence of substances in water is classified
in to three main water impurity groups
1. Suspended Impurities
2. Colloidal Impurities
3. Dissolved Impurities

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1. H2O Introduction con’t…

1. Suspended Impurities
 Suspended impurities include: - clay, algae, fungi,
organic & inorganic matters and mineral matter, etc
 These impurities are dispersion of solid particles
that are large enough to be removed by filtration or
settling
 The suspended particles, which have the same
specific gravity as that of water, are mixed in the
water
 These impurities are macroscopic and cause
turbidity in the water
 The concentration of suspended matter in water is
measured by its turbidity
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2. Colloidal Impurities
 It is very finely divided dispersion of particles in
water
 These particles are so small that can not be
removed by ordinary filters and are not visible to
naked eye
 All the colloidal impurities are electrically
charged and remain in continuous motion and do
not settle due to the repelling actions of the
particles and also very difficult to remove
 The colloidal impurities most of the time
producing the color of water
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1.H2O Introduction con’t…
3. Dissolved Impurities
These dissolved impurities may
contain organic compound, inorganic
salts and gases, etc
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CAUSES OF WATER IMPURITIES
1. Hydrological Cycle
2. Hydro-metrological Influences
3. Man-made Causes
4. Natural Causes
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4. Hydrological Cycle
 Run off
 Seasonal variations
 Rise & fall of the water level and its
influence on the discharge
 etc
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Hydrological Cycle
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2. Man-made Causes
 Improper handling of chemical substances, acids,
salts, oils & oil products
 Dumping of industrial, agricultural & domestic
wastes to water bodies
 The disturbance of hydrological cycle due to
different man made pollutions
 Deforestations
 Lack of awareness of people
(Negligence/carelessness)
 etc….
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3. Hydro-metrological Influences
 Climatic influence
 Air (Movement, Temperature, Humidity,
etc)
 Precipitation
 Evaporation
 etc
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4. Natural Causes
 Absorbing and dissolving gases and
dust particles at the fall of rain.
 Seasonal distributions of precipitation.
 Geographical location of lands.
 Winds
 Erosion
 etc….
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2. WATER QUALITY CHARACTERISTICS
Potable water quality performs the following basic
requirements.
 It should be free from bacteria that causes disease
 free from compounds that cause an offensive taste
& odor
 It should be colorless/clear
 It should not corrode pipes
 it should be free from all objectionable matters
 It should be not saline
 low in concentrations of compounds are acutely or
toxic
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1. WATER QUALITY CHARACTERISTICS con’t…
Water quality characteristics divided
into three main parts:
Physical characteristics
Chemical characteristics
Biological characteristics
Sanitary Survey
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2.WATER QUALITY CHARACTERISTICS
2.1 PHYSICAL CHARACTERISTICS
The physical characteristics of water to drinking
water supply include:
 Temperature
 Turbidity
 Color
 Taste
 Odor
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Blue water = good quality water
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Brown water – river siltation
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2.2 CHEMICAL CHARACTERISTICS
TDS and Conductivity
 EC and TDS are used to grossly estimate the
extent of the ionic species and non-filterable
solids.
 In other words, conductivity is a measure of the
ability of water to conduct an electric current
and is expressed in µS/cm.
 It indicates the physical presence of dissolved
chemicals in the water.
 EC can also be related to the concentrations of
total dissolved solids (TDS) and major ions.
 EC values for most freshwater ranges 10-
1000µS/cm
 Relation EC to TDS - ( 0.55 – 0.7)
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2.2 CHEMICAL CHARACTERISTICS con’t…
PH, Acidity and Alkalinity:-
 pH is a measure of water’s acidity or
alkalinity
 A scale of 0 to 14 used for measurement
 0 < 7 Acidic
 7 Neutral
 7 < 14 Alkaline
 The pH of natural water is usually
governed by lies between 4.5 to 9.5
 pH value is very important for
controlling corrosion & water treatment
processes
 No health based guideline value is
proposed by WHO for pH
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 Alkalinity and Acidity are the base- and acid-
neutralizing capacities of water.
 High Alkalinity are unpalatable and may force consumers
to seek other water sources.
 The acidity of water is controlled by weak acids such as
carbonic as well as by strong mineral acids and
hydrolyzing salts of metals.
 It is determined by titration
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Hardness
 Hardness is the measure of the concentration of calcium and
magnesium salts in water. Total hardiness, divided into carbonate
(temporary) and non- carbonate (constant) harnesses.
 Hardness: - this is the property of water which prevents lather
formation with soap and produces scale in hot water system.
 No health-based guideline for hardness. However, the degree of
hardness in water may affect its acceptability to consumers in terms
of taste & scale deposition (economic disadvantages of hard water
include increased soap consumption and higher fuel cost).
 Soft waters with a hardness less than 100mg/l have a low buffering
capacity and may be more corrosive to water pipes
 Hardness of above 200mg/l can result scale deposition, particularly
by heating
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Category Total Hardness as
CaCO3 (mg/l)
Soft 0 – 60
Moderately hard 61 – 120
Hard 121 – 180
Very hard More than 180
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Classification of water quality based on
Hardness

 Major Ions
 Sodium (Na+) Chloride (Cl-)
 Potassium (K+) Sulfate(SO2-
4)
 Calcium ( Ca2+) Bicarbonate (HCO-3)
 Magnesium (Mg2+)
 Iron (Fe++)
 Major cations (Na+, K+, Ca2+ & Mg2+) and major anions (Cl-,
SO2-
4 & HCO-
3)
 Σ cation= Σ anion
 % difference= 100 (Σ cation- Σ anion)/ (Σ cation+ Σ
anion)
 And the criteria for acceptance is <0.5%
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 Sodium (Na+):- Elevated sodium in certain soil types
can degrade soil structure thereby restricting water
movement and affecting plant growth.
 Sodium in drinking-water and the occurrence of
hypertension, concentrations in excess of 200 mg/litre
may give rise to unacceptable taste
 Potassium (K+):- high concentrations occur in hot
springs and brines,
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Iron
 Naturally the most abundant and exists in two form ferrous (Fe+2)
and ferric (Fe+3) iron. Ferrous iron is found in well waters or
waters without much dissolved oxygen.
 The ferrous iron oxidizes to ferric iron, giving an objectionable
reddish-brown colour to the water.
 Iron also promotes the growth of “iron bacteria’’/nutrient source/
 above 0.3 mg/litre, iron stains laundry and plumbing fixtures.
Manganese
 It don’t usually discolour the water, but stains clothes and
bathroom fixtures.
 Exceeding 0.05mg/litre, manganese in water supplies causes an
undesirable taste and stains sanitary ware and laundry.
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Calcium (Ca2+) & Magnesium (Mg2+)
 The salts of calcium, together with those of magnesium, are
responsible for the hardness of water. Calcium is essential
for all living organisms including plant and practically all
animals.
Chloride (Cl-)
 Chloride in drinking-water originates from natural sources,
sewage and industrial effluents,
 Excessive chloride concentrations increase rates of
corrosion of metals in the distribution system
 chloride concentrations in excess of about 250 mg/litre can
give rise to detectable taste in water
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Bicarbonate (HCO-3):-
 The presence of carbonate and bicarbonate influences the
hardness and alkalinity of water.
Sulfate (SO2-
4)
 The presence of sulfate in drinking-water can cause
noticeable taste, and very high levels might cause a laxative
effect in unaccustomed consumers.
 that taste destruction is minimal at levels below 250
mg/litre.
 Sulfate concentrations in natural waters are usually
between 2 & 80mg/l, although levels may exceed 1000mg/l
near industrial discharges or in arid region where sulfate
minerals are present.
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Fluoride
 Groundwater usually contains higher concentrations than surface
waters
 Excessive fluoride in drinking water causes Fluorosis
 The presence of Calcium in water limits fluoride toxicity
 Fluorosis is less sever when drinking water is hard rather than soft
 Removal of fluoride water is not simple, it requires advanced
water treatment, which are very expensive
 Levels of daily intake fluoride from drinking water depend on the
geographical conditions; in warm area the intake of fluoride
would be relatively high.
 The WHO guideline for fluoride is 1.5mg/l,
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1/6/2023 34
Health impact of high level fluoride in Water
Dental fluorisis

1/6/2023 35

Nitrate & Nitrite
 Nitrogen is an essential nutrient for all aquatic plants
and animals
 The nitrate concentration in groundwater and surface
water is normally low but can reach high levels as a
result of leaching or runoff from agricultural land or
contamination from human or animal wastes
 if water containing nitrate levels greater than 10 mg
NO3
-N/L is used to prepare infant formula it can
result in methemoglobinemia.( blue baby)
 Methemoglobinemia is a condition in which red
blood cells are prevented from transporting oxygen
throughout the body.
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Hydrogen sulfide(H2S)
 The “rotten eggs” odour of hydrogen sulfide is particularly
noticeable in some ground waters and in stagnant drinking-water
in the distribution system, as a result of oxygen depletion and the
subsequent reduction of sulfate by bacterial activity.
 Sulfide is oxidized rapidly to sulfate in well aerated or chlorinated
water.
 The presence of hydrogen sulfide in drinking-water can be easily
detected by the consumer and requires immediate corrective
action.
 The taste and odour thresholds of hydrogen sulfide in water are
estimated to be between 0.05 and 0.1 mg/litre.
1/6/2023 37

Organic Matter Pollution Indicators
 In most instances organic matter pollution is
indicated by the following two parameters.
 Chemical Oxygen Demand(COD)
 Biochemical Oxygen Demand BOD)
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1/6/2023 39
WHO Guideline values for chemicals that are found in drinking-water
Chemical Guideline value
(mg/liter)
Remarks
Arsenic 0.01 Health based
Chromium 0.05 Health based ( For total chromium)
Fluoride 1.5 Volume of water consumed and intake from other sources
should be considered when setting national standards
Manganese 0.4 Health based
Ammonia 1.5 threshold odour concentration
Hardness 500 Not health based
Iron 0.3 Not health based
Hydrogen
sulfide
0.05 Not health based (hydrogen sulfide should not be detectable by
the consumer)
Sodium 200 Not health based
Sulfate 250 Not health based
Copper 2.0 Health based
Lead 0.01 Health based
Nitrate 50 Health based (blue-baby syndrome)

The first priority must be to provide access
for the whole population to some form of
improved water supply.
However, access may be restricted by:
 low coverage,
 poor continuity,
 insufficient quantity,
 poor quality and
 excessive cost relative to the ability
and willingness to pay.
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41

 Thus, in terms of drinking water all these
must be addressed if public health is to
improve.
 The quality of water does, however, have a
great influence on public health; in particular
the microbiological quality of water is
important in preventing ill- health.
 Poor microbiological quality is likely to lead
to outbreaks of infectious water-related
diseases and may cause serious epidemics to
occur.
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42

 water is a vehicle of transmission for many
pathogenic microorganisms of gastrointestinal
origin.
 Diarrhoeal disease may be caused by
consumption of contaminated drinking water
or inadequate availability of water for hygiene
 The microbiological quality of drinking water
is implicated, directly or indirectly, in the
spread of major infectious and parasitic
diseases such as cholera, typhoid, dysentery,
hepatitis, giardiasis, guinea worm and
schistosomiasis.
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43

Water may be polluted in different way
1. Polluted during pre-storage due to
• Human & animal defecation near the water
sources,
• Bathing and cleaning,
• Washing clothes or utensils,
• Release of fertilizer wastes into water,
• Discharge of untreated industrial wastes into
water,
• Mixing of garbage & other soil-borne wastes with
rivers, canals or pond water as runoff during or
after rains,
• Concentration of certain minerals within the soil
becoming exceedingly high.
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2. water become polluted during storage if
 Water collected in unclean utensils,
 Dust particles or insect fall into uncovered
water or it is spoiled by animals,
 Dirty utensils or hands are dipped in stored
water.
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45

 Natural and treated waters vary in
microbiological quality;
 ideally drinking water should not contain any
microorganisms known to be pathogenic.
 It should be free from bacteria indicative of
pollution with excreta.
1/6/2023
46

1/6/2023
MoWR, Water Quality Control Team 47

1/6/2023
MoWR, Water Quality Control Team 48

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