water supply HO new.pptx

DEFENSE UNIVERSITY
COLLEGE OF HEALTH SCIENCES
DEPARTMENT OF PUBLIC HEALTH
Course Title: Ecology and Environmental
Health for health officer students
Course Topic: Water Supply for 2nd year HO
students
By: Lt. Habtamu B.
AUGUST 2021

What’s water supply?
9/22/2022 WATER SUPPLY BY HABTAMU BELAY (Lt.) 2

Water supply
• Water supply is the provision of water by public
utilities, commercial organisations, community
endeavours or by individuals, usually via a system
of pumps and pipes. Aspects of service quality
include continuity of supply, water quality and
water pressure.

Terms commonly used in water supply
• Water table: boundary between water-saturated
ground and unsaturated ground. Below the water
table, rocks and soil are full of water (aquifers).
• Aquifer: an underground zone or layer, which is a
relatively good source of water. It is a rock
formation that bears and yields water when
penetrated.
• Eye of the spring: opening where the water
comes out of the earth.

Cont’d
• Impermeable: not allowing passage of, for
example, a liquid.
• Infiltrate: to pass through a permeable substance,
usually slowly, as if through a filter.
• Palatable water: water that is pleasant to drink
because its taste is good but it may not be safe to
drink.
• Permeable: able to be passed through or
penetrated by a fluid.

Cont’d
• Porosity: the quality of being full of pores and
therefore absorbent and permeable.
• Potable: safe for drinking, free from
pathogens which are introduced to the water
through feces, dirty containers, etc.
• Raw water: water that has not been purified.
• Sedimentation: the action of settling down or
depositing matter in a liquid.
• Turbidity: disturbed, muddy appearance of
water.

INTRODUCTION
• Water is a limited natural resource and a public
good fundamental for life and health. The human
right to water is indispensable for leading a life in
human dignity. It is a prerequisite for the
realization of other human rights. (UN Committee
on Economic, Social and Cultural Rights General
Comment (2002) )
• Water is essential for life. An adequate, safe and
accessible water supply must be available to all
people, and improving access to safe drinking
water can result in tangible benefits to health.
Water is one of the factors which contribute to the
transmission of many diseases.

Cont’d
• In Ethiopia the problems related to water supply
are attributed mainly to lack of maintenance of
the previously constructed systems, lack of
community involvement when the earlier water
systems were built, lack of spare parts and local
maintenance capabilities, etc.
• These problems are magnified particularly in the
rural parts of the country and greatly hamper the
operation even of the minimal water supply
systems available in these areas.

Cont’d
• Because of these facts, the problem still persists
and has contributed a lot to the low safe water
coverage in the country.
• For instance, According to the health indicators of
MOH, the safe water coverage in 1992 E.C. for
urban areas was 83.5%, and 24.7% in the rural
parts of the country where the majority of the
population is living.

Sources of water
• From their origin point of view, there are three main
sources of natural water:
1. surface water (streams, lakes, ponds),
2. groundwater (wells, springs) and
3. rainwater.
• From their location point of view, there are two types of
water sources:
1. those situated above consumption points (they may be
preferable because they may provide water by gravity
and will allow for the construction of systems with less
operation and maintenance requirements) and
2. those situated below consumption points (the water
system will rely on water lifting equipment).

Cont’d
• Water sources can also be described as protected
or unprotected.
Unprotected sources are those where there is no
barrier or other structure to protect the water from
contamination.
Protected sources, on the other hand, are covered
by stonework, cement or other material that
prevents the entry of any physical, chemical or
biological contaminant.

Cont’d
• Water from a protected source is likely to be safe
to drink but water from unprotected sources
cannot be considered safe.
• The terms improved and unimproved sources
may also be used. These terms are broadly
equivalent to protected and unprotected.

Cont’d
• Improved drinking water sources include
household connections, public standpipes and
water points, boreholes, protected dug wells,
protected springs and rainwater collections.
• Unimproved water sources include rivers, lakes,
unprotected wells and unprotected springs.

Ground water
• Groundwater is water found beneath the ground
surface held in the spaces within porous soil and
rock. Groundwater can be obtained from springs,
boreholes or wells. A borehole is a particular type
of well with a narrow shaft.
• Usually a drilling rig is needed to drill (bore) the
hole into the rock. The depth that water is taken
from and the types of rock it has passed through
are important factors that affect the quality of the
groundwater.

Cont’d
• Groundwater, particularly from deep sources, may
provide water of good microbiological quality.
This is because bacteria, protozoa, viruses and
helminthes are ﬁltered from the water as it passes
through the layers of soil and rock into the
groundwater.
• Groundwater sources are therefore preferable to
surface water sources. However, groundwater can
contain chemical contaminants, such as arsenic,
ﬂuorides and nitrates.

Advantages and disadvantages of ground
water
• Advantages:
Safer than surface water
Dependable year rounds
Cheaper (more or less doesn’t need treatment)
Proximity to users
• Disadvantages:
May contain excessive dissolved minerals
May need pumping

Wells
• The practice of obtaining water from wells is
common and well water is an important source of
supply in many developing countries like
Ethiopia. A well should be located uphill from
any possible sources of pollution.
• Wells can be classified based on the depths of
the water-bearing layers as follows:
 Shallow wells
 Deep wells
 Artesian supply

Cont’d
 Shallow wells: tap into water held in aquifers (layers
of water-bearing rock) above the first impermeable
layer. ‘Shallow’ is not a definite depth, but an
indication of the layer of rock from which it is
abstracted.
Deep wells: obtain water from aquifers below at
least one impermeable Layer. A deep well must be
constructed so as to exclude subsoil water and
contamination from above. It should be watertight
down to a point slightly below the level of the
deep supply.

Cont’d
Artesian supply: Water in aquifers is sometimes
under pressure because of the surrounding
impermeable layers and this can cause the water
to flow upwards to the surface. The water level in
the two artesian wells is determined by the level
of the water table.

Contamination of well water
• The causes of bacterial contamination in a well
are usually due to:
Lack of or improper disinfection of a well
following repair or construction.
Failure to seal the space between the drill hole
and the outside of the casing.
Failure to provide a tight sanitary seal at the place
where the pump line(s) passes through the casing.
Wastewater pollution caused by contaminated
water percolating through surrounding soil and
rocks into the well.

Cont’d
• At the time when a new well is constructed or
repairs are made to a well, pump or piping,
contamination from the work is possible.
• Therefore, it is important that the well, pump,
piping and associated structures should be
regularly disinfected using chlorine solution.

Tracing the source of contamination
• There are different methods which help to identify
a possible source of groundwater contamination.
One method is sodium or potassium fluorescein.
• This is a brightly-colored, fluorescent, water-
soluble dye and can be used as a tracer when a
sewage disposal system is suspected of
contaminating groundwater.
• A solution flushed into the disposal system or
suspected source may appear in the well water
within 12–24 hours. It can be detected by sight,
taste or analysis.

Springs
• A spring occurs at the point where the boundary
between a permeable layer of underground rock and
an impermeable layer reaches the ground surface.
• Rainwater percolates (trickles down) through the soil
into permeable layers of subsoil or underground rock.
• The downward percolation will be stopped if this
layer sits on top of an impermeable layer and the
water can go no further.
• Depending on the slope of the layers, the water will
run along the top of the impermeable layer to a point
where it reaches the surface and emerges as a spring.

Rainwater
• Rainwater can be used for domestic purposes in areas
where there are no alternative sources of water such
as springs, rivers and lakes, or where these sources of
water are contaminated.
• The term rainwater harvesting is sometimes used. It
simply means collecting, or harvesting, rainwater as it
runs off from hard surfaces such as rooftops and
storing it in a tank or cistern (Figure below).

Cont’d
• The main advantage of rainwater is that it is free. It is
fairly reliable though obviously dependent on the
amount of rain that falls. It does not usually require
pumps or pipes and is available at the doorstep.
• Using rainwater can reduce the burden on women and
children who typically are the water carriers in
Ethiopia and walk long distances to fetch inadequate
supplies.

Fig. Rainwater is collected from the roof (Photo: Pam
Furniss)

Surface water sources
• All surface water sources are subject to
continuous or intermittent pollution and must be
treated to make them safe to drink.
• One never knows when the organisms causing
diseases such as typhoid fever, gastroenteritis,
giardiasis or infectious hepatitis A will
contaminate surface water sources.
• The extent of the treatment required will depend
on the results of a sanitary survey made by an
experienced professional, including physical,
chemical and microbiological analyses.

Cont’d
• Protecting surface water from pollution is difficult
because, as noted earlier, the activities of
upstream users of the river water will affect the
quality of the water for downstream users and the
land use in the surrounding area will also have an
impact.
• Surface waters are, by definition, unprotected
sources.

Cont’d
• Surface water is liable for contamination because
pollutants can enter waterways by a number of
different routes. There are two typed of
pollution sources:
1. Point source: pollutants which enter a water
way from a specific point though a pipe,
ditch, culvert (channel), etc. e.g. sewage
treatment plants, industrial discharges.
Although relatively easy to collect and treat
yet point sources have been the most
conspicuous violators of water quality.

Cont’d
2. Non-point sources/multiple sources: pollutants, which
runoff or seep into waterways from broad areas of land
rather than entering through a discrete pipe or conduit.
• These are what are actually considered significant
contributors to water contamination.
• They result primarily from a variety of human land use
practices and including soil erosion, construction
activities, animal feedlot runoff, pesticides and fertilizers
runoff, urban street runoff and fallout of airborne
pollutants.
• These sources are also known as diffuse pollution. The
problems in identifying the exact point of origin make non-point
sources much more difficult to control.

Importance of water
• The following points elaborate the importance
of water:
1. It is impossible to have a clean and sanitary
environment without water. Water is necessary in
promoting personal hygiene and in cleaning the
environment. Without an adequate and
wholesome water supply, health cannot be
maintained.
2. Water is essential for life. Man can live nearly
two months without food, but can live only three
or four days without water. In general 70% of
human body weight is water and a human being
needs two liters of water per day as minimum.

Cont’d
3. Most of the foods that man eats contain water.
For example:
Milk contains about 88% water;
Egg contains about 66% water;
Fish are 80% water;
Potatoes are 75% water;
Beef is 77% water.

Cont’d
4. It is essential to run industries. Nearly all modern
industries are thirsty; they need water. For example:
It takes about 10 liters of water to produce one
litter of petrol;
It takes about 600 liters of water to produce 1kg
of woolen cloth;
It takes about 3500 liters of water to produce 1kg
of dry cement.

Cont’d
5. It’s important for the balance in ecology (i.e. the
balance in relationship between living things and the
environment in which they live).
All animal life depends directly or indirectly upon
vegetation for food, and vegetation will not grow
without water.
Vegetable matter, such as leaves and steams, can
be converted to soil by bacterial action. Bacteria
need water in order to thrive.
New plants growing in this soil take up nutrients
through their roots in the form of a solution in
water. Any break in this ecological chain can
mean failure of the whole ecological system.

Cont’d
6. Water is important for agriculture, animal
breeding and fishing.
7. Water is a valuable source of energy. It is capable
of generating hydroelectric power.
8. Water facilitates transportation and navigation.
For example, the Baro River is one of the rivers
used for boat transportation in Ethiopia.
9. Water plays an important role in recreation
activities. Lake Langano is an attractive lake for
recreation.

Public Health Importance of Water
• Water is a basic necessity for life. Unfortunately,
not all water helps human to survive. Water from
contaminated sources causes numerous diseases
and untimely deaths.
• The fact that a human needs of water and cannot
live without it forces him to use it even for
drinking purposes, from any source, whether pure
or contaminated,

Cont’d
• As a result, many people suffer or die from
waterborne diseases. Hence, every country has to
take preventive measures to avoid pollution and
contamination of the available water resources.
• Therefore, public water supply must be potable,
palatable and wholesome. Water must not have
disagreeable physical change and must be
hygienically safe.

Water pollution
• Water pollution: the release of substances into
subsurface groundwater or into lakes,
streams, rivers, and oceans to the point where the
substances interfere with beneficial use of
the water or with the natural functioning
of ecosystems. (https://www.britannica.com/)
• In addition to the release of substances, such
as chemicals or microorganisms, water pollution
may also include the release of energy, in the
form of radioactivity or heat, into bodies of water.

Sources of water pollution
• Water quality can be affected by pollution from point
sources and non-point sources.
• Point sources are identifiable points or places, such as
a pipe or channel, which discharge directly into a body
of water. This might be from wastewater treatment
plants, factories and industrial plants, latrines, septic
tanks or piped discharge from barnyards and other
places where livestock are confined.
• Non-point sources are those where pollution arises
over a wider area and it is often difficult to locate the
exact place of origin. For example, fertiliser or
pesticide washed from a field by rain may seep into a
river or stream at many places both on the surface and
through the soil.

Cont’d
• Pollution from non-point sources, also known as
diffuse pollution, contributes most of the
contaminants in rivers and lakes.
• Other non-point sources are pollution from
construction sites and other land disturbances.
• The problems in identifying the exact point of
origin make non-point sources much more
difﬁcult to control.

Public health impacts of water pollution
• Waterborne infectious diseases are transmitted
primarily through contamination of the water
sources with excreta of humans and animals who
are either active cases or carriers of disease.
• Carriers do not show any signs of disease
although they have disease-causing agents in their
body that can be transferred to others; active cases
are people who are displaying visible signs of
disease.
• Use of contaminated water for drinking or
cooking, or contact with contaminated water
during washing or bathing, may result in
infection.

Cont’d
• The dose or amount ingested that is necessary to
cause illness depends on the type of pathogen.
Exposure to a single pathogenic organism does
not always result in infection and disease.
• Sometimes many pathogens, perhaps several
hundred, must be ingested to cause infection. The
minimum infectious dose also varies with the age,
health, nutritional and immunological status of
the exposed individual.
• Infants and young children, people who are
debilitated, people who are living in unsanitary
conditions, people who are sick and the elderly
are at greatest risk of waterborne diseases.

Control of water pollution
• The control of pollution should ideally take place
at the point of generation, or, in other words, it
should be prevented at source.
• The control of excess nutrients is an important
issue both from a public health perspective and to
keep natural waters free from eutrophication.
• An increasing proportion of water pollution
originates from diffuse (non-point) sources, such
as agricultural use of fertilisers.

Cont’d
• Farmers may need guidance on good agricultural
practices that will help reduce water pollution
from agriculture. For example, the amount of
fertiliser used and the timing of its application can
make a signiﬁcant difference.

Cont’d
• Pollution prevention is best achieved by ensuring
that each potential point source is properly sited,
designed, constructed and managed; the aim
being to contain the pollutants and prevent their
uncontrolled release to the environment.
• Sources of pollution should be sited as far from
watercourses as possible (at least 15 m away) and
below any water sources on the site.
• Appropriate use of excreta disposal, solid waste
disposal and animal waste disposal will help
prevent contamination of both surface and
groundwater.

Water and disease
• The saying “water is life” is found in many
cultures around the world. It underscores the fact
that clean water is an absolute prerequisite for
healthy living.
• The importance of water in human welfare cannot
be over-emphasized. The normal functioning of
the human body depends entirely upon an
adequate quantity and quality of water.
• But if the water is from contaminated sources, it
causes numerous water-associated diseases.

Cont’d
• In the developed world, water-associated disease
are rare, due essentially to the presence of
efficient water supply and waste water disposal
systems.
• However, in the developing world, the majority of
people are without a safe water supply and
adequate sanitation.

Water-associated Disease
• Water-associated disease can be defined as a
disease in relation to water supply and sanitation.
• There are four categories:
1. Waterborne disease
2. Water-washed disease
3. Water-based disease
4. Water-related disease

1. Waterborne diseases
• Waterborne diseases are those caused by ingestion
of water that is contaminated by human or animal
excrement and contains pathogenic
microorganisms. Transmission occurs by drinking
contaminated water.
• Several infections enteric or intestinal diseases of
man are transmitted through water contamination
by fecal matter.
• Pathogens excreted in water by an infected person
include all major categories such as bacteria,
viruses, protozoa and parasitic warms.

Waterborne diseases with their etiologies
Types of organism Disease Type
Bacteria • ƒ
Typhoid and paratyphoid fever ƒ
• Cholera ƒ
• Diarrheas (caused by salmonella,
yersinia entrocolitica, E.coli) ƒ
• Campylobacter dysentery ƒ
• Bacillary dysentery (caused by
shigella)
Virus • Hepatitis A ƒ
• Poliomyelitis ƒ
• Viral gastroenteritis
Protozoa • Amoebic dysentery ƒ
• Giardia (lambliasis) ƒ
• Balantidiasis
Helminthes • Helminthiasis caused by Ascaris and
Trichinas

The classic waterborne disease infection cycle

F-diagram: routes of transmission of infectious
diarrheal disease to a new host

2. Water-washed diseases
• These comprise diseases linked to a lack of water for
personal hygiene.
• They occur when there is insufficient clean water
for washing and personal hygiene, or when there is
contact with contaminated water.
• They are also sometimes known as water-scarce
diseases because they occur when there is not enough
water available for adequate personal washing.

Cont’d
• Examples of water -washed diseases are: ƒ
Dermatological disease such as scabies ƒ
Ophthalmic disease such as trachoma and
conjunctivitis
Louse-borne diseases such as louse borne typhus
and relapsing fever.
• Lack of good personal hygiene and inability to
wash clothes encourages the proliferation of lice
and the problems associated with their presence
(itching, scratching, skin sores).
• To prevent this type of disease, provision of an
ample amount of water and personal hygiene are
very essential.

3. Water-based diseases/ water impounding
diseases
• These are diseases caused by infectious agents
that are spread by contact with water. The
essential part of the life cycle of the infecting
agent takes place from an aquatic animal.
• A number of diseases depend upon the pathogenic
organisms spending part of their life cycle in
water or in an intermediate host which lives in
water. Thus, infection of humans cannot occur by
immediate ingestion of, or contact with, the
organism excreted by sufferers.

Cont’d
• Many of the diseases in this class are caused by
worms, which infest the sufferer and produce
eggs, which are then discharged in feces or urine.
• Typical examples are Schistosomiasis (Bilharzia)
and Dracunculiasis (guinea worm).
• These diseases are usually passed to humans
when they drink contaminated water or use it for
washing.
• People can become infected from swimming or
wading (to walk through water) in infected water.

The cycle of transmission of Schistosomiasis

Dracunculiasis (guinea worm)

Cont’d
• To prevent this group of diseases, the following
methods may be implemented:
Avoidance of contact with and ingestion of
contaminated water.
Reduction of intermediate hosts (snail) by using
“endod” or Lemma toxin.
1.Storage of water from 24 to 72 hours to kill the
cercaria (a free-swimming larval stage in which a
parasitic fluke passes from an intermediate host
(typically a snail) to another intermediate host or
to the final vertebrate host).

4. Water-related diseases
• These are diseases transmitted by insects that live
close to water. Infections are spread by
mosquitoes, flies and other insects that breed in
water or near it.
• There are a number of diseases which are spread
by insects that breed or feed near water so that
their incidence can be related to the proximity of
suitable water sources.
• Infection with these diseases is in no way
connected with human consumption or contact
with the water.

Cont’d
• Example: Malaria, sleeping sickness, yellow
fever, onchocerciasis, etc.
• To prevent this type of disease, making the water
unsuitable for breeding of insects is essential.

Summary
• All the waterborne and many of the water-based
diseases depend for their dispersion on infecting
agents from human feces getting into drinking
water or into food.
• The chain of disease transmission may be broken
effectively by sanitary disposal of feces and the
provision of safe and adequate water supplies.

Cont’d
• Improvement in the reality of community water
supplies will basically only affect the waterborne
disease such as bacillary dysentery, cholera and
typhoid.
• Many of the diarrheal diseases probably are due
more to a lack of safe and adequate quantities of
water. Skin and eye infections are in this group of
water-associated diseases.

The four mechanisms of water-associated diseases and
preventive strategies

Water Treatment
• is defined as the process of removing all those
substances, whether biological, chemical or physical,
which are potentially dangerous or undesirable in
water supply for human and domestic use.

Main objective of water treatment
1. To remove pathogenic organisms and
consequently to prevent waterborne disease.
2. To remove substance which impart color, taste or
odor to the water.
3. To remove excess or undesirable chemicals or
minerals from the water.
4. To regulate essential elements or chemicals that
may be in excess or lacking in a certain water
supply (e.g. fluoridation or defluoridation of
water, softening of water, etc.)
5. To remove excess or undesirable dissolved
gasses.

Water treatment systems
• Water treatment systems can be categorised as:
1. small-scale water treatment, which includes
community and household treatment methods, or
2. large-scale water treatment that might be
found in towns and cities.

Small-scale water treatment systems
• Household- and community-level treatment systems are the
methods most likely to be used in rural areas.
• Household-level water treatment is appropriate when:
 A relatively small amount of water is obtained from a well
or spring and is collected and transported by hand.
 The source is contaminated and simple protective measures
can neither improve water quality nor stop the
contamination.
 Community resources are inadequate to meet the cost of a
simple community treatment system and make it difﬁcult to
develop a centralised treatment system.
 An emergency situation causes disruption of the service
and contamination of the water supply so that a long-term
rapid solution is needed.

Community-level water treatment is
appropriate when:
A water source serves a larger population than can
be served by household level or individual
treatment systems.
A community water source is contaminated and
simple protective measures can neither improve
water quality nor stop the contamination.
Community resources are adequate to cover the
cost of construction, operation and maintenance
of a simple community-level treatment system.

Methods of small-scale water treatment
• There are several different methods of small-scale
water treatment that can be employed at the
household and community level.
• Broadly speaking these can be grouped either as:
• ﬁltration methods, in which water passes through
a porous barrier (ﬁlter) that traps tiny particles
including pathogenic microorganisms and other
impurities, and
• disinfection methods, in which contaminants are
removed by the use of various chemicals or by
energy from the sun.

Household sand filter
• The upper pot contains layers of sand and gravel. Water
is poured in at the top and, as it passes through the
layers of sand, any particles within it are filtered out.
• The thickness of the layers should be approximately 5
cm of gravel, 5 cm of coarse sand and 10 cm of fine
sand.
• The bottom of the upper pot should be perforated (have
tiny holes in it) so the clean water can drip into the
lower pot.
• The lower pot should have a tap (faucet) to draw off the
clean water easily (see Figure below). The sand and
gravel should be changed when the rate of filtration
starts to slow; at minimum it should be changed every
two or three months.

Household water ﬁlter using two clay pots
placed on top of each other

Cloth filtration
• Cloth filtration can be very effective against cholera,
guinea worm (dracunculiasis) and other disease-causing
agents. By following the procedures and practice
yourself, you can demonstrate this for communities you
are working with.
• The steps in cloth filtration are:
 Use a large cloth, preferably made of finely-woven
cotton. The cloth must be big enough to easily cover the
opening of the container once it has been folded.
 Fold the cloth at least four times so there are multiple
layers of fabric and place this over the opening of the
storage vessel.

Cont’d
Fasten the cloth securely around the rim of the
opening and tighten the string. If reusing the
cloth, always use the same side up each time.
Filter all water immediately at source as it is
being collected.
Always keep filtered water separated from non-
filtered water.
Rinse the filter cloth after each use, with a final
rinse using cloth-filtered water, and then leave the
cloth in the sun until it is dry.
Clean the cloth regularly using soap and replace it
as soon as there are any visible tears or holes.

Cloth ﬁltration

Solar disinfection
• Solar disinfection, also known as SODIS, relies on
energy from the sun to kill pathogenic organisms,
especially bacteria.
• Ultraviolet light from the sun is an effective bactericide
for water. This simple technique requires only a few
plastic bottles and sunlight.
• Firstly, collect several bottles (0.3 to 2.0 litre) made of
clear plastic, remove all labels and wash them
thoroughly.
• Fill the bottles with water of low turbidity and shake for
about 20 seconds to aerate the water.

Cont’d
• Expose the bottles to the sun by placing them on a
roof or rack for at least six hours (if sunny) or two
days (if cloudy) (see Figures below). The water is
now ready to drink.

Chemical disinfection methods
• There are several commercially available products
designed for treating water at household level.
 Chlorine solution
• Chlorine solution, also known as sodium hypochlorite
solution or bleach, is the most affordable, easiest to
produce, and most widely available chemical for
household water treatment.
• It is supplied in bottles and has easily interpretable
instructions for use on the side of the bottle.
• Typically, the procedure is to add a capful of chlorine
solution to a 25 litre water storage container, then shake
and wait for 30 minutes chlorine contact time before
drinking. Double dosing is advisable if the water is
visibly dirty.

Cont’d
 Aquatabs
• Aquatabs are a speciﬁcally formulated and branded
solid form of sodium dichloroisocyanurate (NaDCC)
(see Figure 14.6). NaDCC is stable in Aquatabs form as
a solid which gives it a longer shelf life and makes
storage, handling and transport much easier than with
liquid bleach. One Aquatab contains 67 mg of NaDCC
and treats 20 litres of clear water. For visibly turbid
water, two tablets per 20 litres are needed. It is very
important to mix well and leave for 30 minutes contact
time before consumption.

Cont’d
 PUR
• ‘PUR Purifier of Water’ is the brand name of a combined
flocculant and disinfectant product produced by Procter and
Gamble. It is now on the market in Ethiopia although it may
not be widely available across the country.
• PUR can be used to treat raw source waters with a wide
range of turbidity and pathogen load.
• This water treatment chemical allows flocculation to take
place and helps to remove Giardia and Cryptosporidium
cysts that are resistant to chlorine disinfection.
• (A cyst is a dormant stage in the life cycle of some protozoa
and bacteria that is resistant to adverse environmental
conditions and therefore difficult to destroy.) PUR comes in
sachets with one sachet needed to treat 10 litres of water.

Cont’d
 Wuha Agar
• Wuha Agar is a chlorine-based water treatment
solution that is used in Ethiopia. The procedure is
very similar to other chemical treatment methods. For
a 20 litre jerrycan, add one capful of Wuha Agar,
cover and shake. After 30 minutes contact time you
can use it.

Some chlorine compounds with their chlorine
concentration

Boiling
• Boiling is also an optional water treatment at household
level. Boiling is a simple way of killing any ova (eggs),
cysts, bacteria and viruses present in contaminated
water. Water should be heated until large bubbles are
continuously coming to the surface of the water.
• The disadvantage of boiling as a treatment method is
that it requires large amounts of fuel, so cost may
prevent people from using this method.
• Also, boiling may give an unpleasant taste to the water,
which may be unacceptable, and very hot water can
cause accidents in the home. Boiled water can become
recontaminated once it has cooled.

Safe storage
• Whatever type of treatment method is used, it is
essential that water is stored safely and hygienically.
• Even if water has come from an improved source, this
will not guarantee that it is safe because contamination
can occur in the household due to poor storage and
handling practices.
• The principal health risk associated with household
water storage is the ease of recontamination,
particularly where the members of a family or
community do not all follow good hygiene practice.
• Safe storage is especially designed to eliminate sources
of recontamination by keeping objects, including hands,
out of the system.

Large-scale water treatment
• Large-scale or municipal water treatment is not
common in rural communities but you may ﬁnd it in
larger towns and cities where there is a network of
pipes and pumps to distribute water from the
treatment works.
• There are several steps in municipal water treatment
intended to remove solids, kill pathogenic organisms
and make water safe to drink.
• The main stages usually are aeration, sedimentation,
coagulation, ﬁltration and disinfection.

Cont’d
• Aeration simply means to mix air with the water.
It is used to remove volatile (easily evaporated)
substances from drinking water.
• Air and water are put into contact with each other,
i.e. air is bubbled through the water, so that the
volatile substances are evaporated into the
airstream and removed from the water.
• Aeration can be carried out in towers or aeration
basins to provide the necessary contact time
between air and water.

Cont’d
• Sedimentation is the settling out of
comparatively heavy suspended material
(suspended solids) in water because of gravity.
The settling takes place in a quiet pond or a
specially constructed tank.
• A minimum 24-hour retention time is necessary to
have a signiﬁcant reduction in suspended matter.
(Retention time means the length of time the
water is kept (retained) in the tank.)
Sedimentation can be used alone or in
combination with coagulation.

Cont’d
• Coagulation is the formation of particles in a liquid by
adding chemicals. Its meaning is similar to flocculation.
The flocculant used in large-scale treatment plants is
usually alum (hydrated aluminum sulphate). This
chemical is mixed with turbid water and then allowed
to remain still in a sedimentation tank or basin so that
the larger particles, or floc, settle to the bottom.
• Filtration is the removal of suspended material from
water as it passes through beds of porous material. This
is exactly the same principle as filtration methods at
household level. Filters can be made of layers of sand,
gravel or charcoal. Filtration cannot completely remove
all bacteria.

Cont’d
• Disinfection kills most harmful organisms
including pathogenic bacteria. Without
disinfection, the risk from waterborne disease will
remain.
• Disinfecting agents include chlorine, ultraviolet
light, ozone, iodine and others but, of these,
chlorine is the most frequent treatment agent. The
process is called chlorination.

Chlorination
• Chlorination, used at both household and large-
scale levels, is one of the most effective and
widely used methods for disinfecting water and
making it safe to drink.
• Whatever the level, it is important that the correct
quantity of chlorine is added to remove all
impurities.

Cont’d
• At municipal level, various terms are used to describe
aspects of the chlorination process.
• Chlorine dosage is the amount of chlorine added to the
water system in milligrams per litre (mg/l).
• Chlorine demand is the amount of chlorine that
combines with the impurities and therefore is no longer
available as a disinfecting agent.
• The chlorine that remains in the water after the chlorine
demand has been satisﬁed is called free chlorine
residual.
• A certain amount of residual chlorine is a good idea
because it protects against future recontamination.

Cont’d
• The orthotolidine-arsenite test (OTA) is used to
determine the amount of free chlorine residual.
• When orthotolidine reagent is added to water
containing chlorine, a greenish-yellow colour will
appear. The intensity of the colour is measured
against a chart to determine the amount of free
available residual chlorine in the water.
• The amount of residual chlorine needs to be in the
range of 0.2–0.5 mg/l if it is to prevent
recontamination with bacteria.

The beneﬁts of point-of-use chlorination
include:
• Chlorine is proven to be effective in the reduction
of bacteria and most viruses.
• The residual chlorine is effective in protection
against recontamination.
• It is easy to use.
• Chlorine is easily available at low cost.

The drawbacks of chlorine treatment include:
• It provides relatively low protection against some
viruses and parasites.
• Lower effectiveness in water contaminated with
organic and certain inorganic compounds.
• Potential objections to taste and odour.
• Some people have concerns about the potential
long-term carcinogenic effects of chlorination by
products.

Water quality standard
• Introduction
• It is estimated that 80 % of all diseases and over
one-third of deaths in developing countries are
caused by the consumption of contaminated water
and, on average, as much as one–tenth of each
person’s productive time is lost to water-related
disease.
• The cause for these problems is contaminated
water with pathogenic micro-organisms and
harmful chemical substances.

Cont’d
• Therefore, provision of potable water is very
important to reduce these problems, as well as
developing drinking water standards with special
emphasis on:
 aesthetic,
 physical,
 chemical,
 bacteriological and
 sanitary surveying of drinking water supply so as to
reduce suffering and death in the community.

Aesthetic and Physical Analysis
• Aesthetic parameters are those detectable by the
senses, namely turbidity, color, taste, and odor.
• They are important in monitoring community
water supplies because they may cause the water
supply to be rejected and alternative, and possibly
poorer quality, sources to be adopted.
• Additionally, they are simple and inexpensive to
monitor qualitatively in the field.

Color
• Color in drinking water may be due to the presence of
colored organic matter, (e.g. humic substances), metals
such as iron and manganese, or highly colored
industrial wastes.
• Drinking water should be colorless. For the purposes of
surveillance of community water supplies, it is useful to
note the presence or absence of observable color at the
time of sampling.
• Changes in the color of water and the appearance of
new colors serve as indicators that further investigation
is needed.

Taste and odor
• Odors in water are caused mainly by the presence
of organic substances. Some odors are indicative
of increased biological activity; others may results
from industrial pollution.
• Sanitary inspections should always be made to
correct an odor problem.
• Taste problems, which are sometimes grouped
with odor problems, usually account for the
largest single category of consumer complaints.

Turbidity
• Turbidity is important because it affects both the
acceptability of water to consumers, and the selection
and efficiency of treatment processes, particularly the
efficiency of disinfection with chlorine since it exerts a
chlorine demand and protects micro-organisms and
may also stimulate the growth of bacteria.
• In all processes in which disinfections are used, the
turbidity must always be low, preferably below 1 NTU
or (these units are interchangeable in practice).
• It is recommended that, for water to be disinfected, the
turbidity should be consistently less than 5 NTU or /
and ideally have a median value of less than 1 NTU.
• The instrument used for measuring it is called
nephelometer or turbidimeter.

Chemical Analysis
• Under ideal conditions, water meant for drinking
and domestic uses should not contain above the
maximum allowable concentration of chemicals
that may be harmful, objectionable or
economically undesirable.
• The maximum allowable concentration (MAC) or
the permissible dose of a toxic substance is "a
definable and measurable level of human
exposure at some point above zero, below which
there is no significant threat to human health".

Hydrogen ion concentration (PH)
• The PH of water is a measurement of how much
acid or alkali is in it, the PH scale being marked
from 0 to 14. A PH of 0 is extremely acid, while a
PH of 14 is extremely alkaline.
• A scale reading of 7 indicates a neutral point. The
PH values of natural water range from slightly
acidic to slightly alkaline, running from 5.5 to 8.5.

Cont’d
• Ideally, drinking water should be neutral or
slightly alkaline, PH 7.0 to 8.5. Water that is acidic
is corrosive; it affects the solubility factors of the
various chemicals that might be in the water, and
hence affects the process of water treatment.
• On the other hand, water on the alkaline side of
the scale reduces the disinfection efficiency of
chlorination, etc.

Hardness
• Hardness of water is divided into temporary and
permanent hardness. The two hardnesses
considered together are called Total Hardness.
• Analyses of total hardness are usually expressed
in terms of CaCO3 equivalent (mg/l of CaC03).
• Hard water wastes soap, forms scale in boilers,
and may act as a laxative under extreme
conditions.

Chlorides
• Sodium chloride or common salt dissolves easily
in water. The content of chloride in natural
surface waters is generally insignificant, but
groundwater may contain excessive amounts of
chloride, particularly where the rock formation of
a region contains salt deposits.
• In other cases, the presence of excessive
concentrations of chlorides may be due to
contamination of the water by sewage (urine
concentration of chlorides is in the order of about
5000 mg/l), or the mixing of salty water from
coastal areas with fresh water. In any case, the
concentration and the source of the chlorides in
water supply must be determined.

Cont’d
• Water that contains high concentrations of
chlorides has an unpleasant taste; the level at
which this objectionable taste is noticeable
depends on the individual.
• WHO’s international standards for drinking water
(1971) indicate 200 mg/l as the highest desirable
level, and 600 mg/l as the maximum permissible
level of chlorides in drinking water.

Iron and manganese
• Iron and manganese are usually considered
together because they usually occur together in
groundwater, and their chemical behavior is
similar.
• Iron and manganese, when present in excess of
the optimum level of concentration, impart a
brown-to-reddish color to the water, and they
stain clothes washed in such water.
• They also affect the taste of water, and their
removal to an acceptable level (MAC: iron as Fe
0.3 mg/l, and manganese as Mn 0.5 mg/l) is
essential in water treatment.

Lead
• Lead (Pb) is one of the toxic elements that may be
present in a water supply, but which is not
normally found in natural waters.
• However, lead dissolves in water that is acidic,
and will contaminate water that is conveyed
through lead pipes, collected over lead-painted
surfaces or stored in lead-coated containers, etc.

Cont’d
• Lead can also reach water through industrial
wastes. Lead poisoning is cumulative; that is, it
increases with every addition of lead in the human
system, which cannot get rid of it; and it causes
various forms of paralysis.
• The maximum allowable concentration that can
be permitted in water without ill effects is
established to be less than 0.01 mg/l.

Bacteriological Analysis
• The principal risk associated with water in
community supplies is that of infectious disease
related to fecal contamination.
• Hence, the microbiological examination of
drinking water emphasizes assessment of the
hygienic quality of the supply.
• Indicator organisms may be used to assess the
efficiency of drinking water treatment plants,
which is an important element of quality control.
• The isolation of specific pathogens in water
should be undertaken for the purposes of
investigating and controlling outbreaks of disease.

Bacterial indicators of fecal pollution
• The use of normal intestinal organisms as
indicators of fecal pollution rather than the
pathogens themselves is a universally accepted
principle for monitoring and assessing the
microbial safety of water supplies.

Bacteria indicators
• Bacteria indicators/tracers of fecal contamination
ideally should fulfill the following requirements.
They must:
a) Be applicable to all types of water
b) Always be present when pathogens are present
c) Always be absent when pathogens are absent
d) Be easy to detect and count, and detectable in low
densities
e) Be non-pathogenic for the safety of laboratory
personnel

Cont’d
f) Be a normal member of intestinal flora of healthy
people
g) Be exclusively intestinal inhabitants, hence
exclusively facal in origin when found in the
environment
h) Unable to multiply outside the intestine.

Cont’d
• No bacterial species or group presently in use
completely fulfill all these requirements. But a few
come close to doing so.
• In conventional water bacteriology, three main groups
or species of bacteria are used as fecal indicators:
1. Coliform bacteria (E. -coli, Citrobacter, Entrobacter,
klebsiella)
 Total coliform (TC)
 Fecal coliform (FC)
 Non-fecal coliferm (NFC)

Cont’d
2. Fecal streptococci (FS) or Entrococcus - e.g.
streptococus
fecalis
3. Clostridium perfringens (Cl. Welchi).

Compulsory Ethiopian Standard
for Drinking Water
• Physical Characteristics of Drinking Water
Characteristics Maximum permissible level
Odor Unobjectionable
Taste Unobjectionable
Turbidity, NTU 5
Color, TCU 15

Characteristics that Affect the Palatability of Drinking Water
Substance or characteristic Maximum permissible level
Total hardness (CaCO3) mg/L 300
Total dissolved solids mg/L 1,000
Total Iron (Fe) mg/L 0.3
Manganese (Mn) mg/L 0.5
Ammonia (NH3+NH4+) mg/L 1.5
Residual free chlorine mg/L 0.5
Magnesium (Mg) mg/L 50
Calcium (Ca) mg/L 75
Copper (Cu) mg/L 2
Zinc (Zn) mg/L 5
Sulfate (SO4) mg/L 250
Chloride (Cl) mg/L 250
Total alkalinity (CaCO3) mg/L 200
Sodium (Na) mg/L 200
Potassium(k) mg/L 1.5
pH value, units 6.5 to 8.5 (permissible range)
Aluminum (Al) mg/L 0.2

Content of Toxic and/or Disease-causing Substances
in Drinking Water
Substance or characteristic Maximum permissible level
Barium (Ba) mg/L 0.7
Total mercury (Hg) mg/L 0.001
Cadmium (Cd) mg/L 0.003
Arsenic (As) mg/L 0.01
Cyanide (CN) mg/L 0.07
Nitrate (NO3) mg/L 3
Lead (Pb) mg/L 0.01
Boron (B) mg/L 0.3
Selenium (Se) mg/L 0.01
Fluoride (F) mg/L 1.5
Chromium (Cr) mg/L 0.05

Bacteriological levels
Organism Maximum permissible
level
Total viable organisms,
colonies per mL
Must not be detectable
Fecal streptococci per 100
mL
Coliform organisms,
number per 100 mL
E. coli, number per 100
mL

Water requirement
• According to the WHO, each of us needs 30–40 litres
of water a day for all domestic purposes.
• Safe drinking water and adequate sanitation are
crucial for poverty reduction, crucial for sustainable
development and crucial for achieving any and every
one of the Millennium Development Goals, Ban Ki-
moon, former UN Secretary General.
• 884 million people in the world do not have access to
safe drinking-water.
• 2.6 billion people lack access to basic sanitation, 40%
of the world’s population.

How much water does an individual use?
• People use water for a wide variety of activities.
Some of these are more important than others.
• Having a few litres of water to drink each day, for
example, is more important than having water for
personal hygiene or laundry, but people will still
want and need to wash for the prevention of skin
diseases and meeting other physiological needs.
• Other uses of water have health and other benefits
but decrease in urgency as Figure below
demonstrates.

Hierarchy of water requirements (after
Maslow’s hierarchy of needs)

Simplified table of water requirements for
survival (per person)

Priorities for water
• People do not always have predictable needs. In
some cultures, the need to wash sanitary towels or
to wash hands and feet before prayer may be
perceived to be more important than other water
uses.
• Talk to people to understand their priorities.
People may also have quite specific needs
concerning the use of water for anal cleansing.

Cont’d
• Women and men may have different priorities. Women
may be concerned about basic household water
requirements and water to wash during menstruation,
whilst men may have concerns about livestock.
• In the assessment, waste spillage and leaks also need to
be taken into consideration. The Sphere Standards
suggest a basic survival-level water requirement to use
as a starting point for calculating demand.
• However, research indicates that 20 liters per capita per
day is the minimum quantity of safe water required to
realize minimum essential levels for health and
hygiene.
• Therefore, efforts should be made to incrementally
secure this amount for each individual.

Sanitation and water requirement
• The type of sanitation provided has a big impact
on water requirement.
• Water-borne types of sanitation, such as flush
toilets, require a large volume of water (up to 7L
per person per use).
• Pit latrines, or simple pour-flush toilets have a
much lower water requirement.

Sufficient
• The water supply and sanitation facility for each
person must be continuous and sufficient for
personal and domestic uses.
• These uses ordinarily include
drinking,
personal sanitation,
washing of clothes,
food preparation and
personal and household hygiene.
• According to the World Health Organization
(WHO), between 50 and 100 litres of water per
person per day are needed to ensure that most
basic needs are met and few health concerns arise.

Cont’d
• Most of the people categorized as lacking access to
clean water use about 5 litres a day-one tenth of the
average daily amount used in rich countries to flush
toilets. UNDP. Human Development Report 2006.
Beyond Scarcity: Power, poverty and the global water
crisis. 2006
• Most people need at least 2 litres of safe water per
capita per day for food preparation. WHO. The right to
water. 2003
• The basic requirement of drinking water for a lactating
woman engaged in even moderate physical activity is
7.5 litres a day. UNDP. Human Development Report
2006. Beyond Scarcity: Power, poverty and the global
water crisis. 2006

Safe
• The water required for personal or domestic use
must be safe, therefore free from micro-
organisms, chemical substances and radiological
hazards that constitute a threat to health.
• Measures of drinking-water safety are usually
defined by national and/or local standards.
• WHO’s Guidelines for drinking-water quality
provide a basis for the development of national
standards that, if properly implemented, will
ensure the safety of drinking-water.

Cont’d
• Everyone is entitled to safe and adequate
sanitation. Facilities must be situated where
physical security can be safeguarded. Ensuring
safe sanitation also requires substantial hygiene
education and promotion.
• This means toilets must be available for use at all
times of the day or night and must be hygienic;
wastewater and excreta safely disposed and toilets
constructed to prevent collapse.
• Services must ensure privacy and water points
should be positioned to enable use for personal
hygiene, including menstrual hygiene.

Physically accessible
• Everyone has the right to water and sanitation
services that are physically accessible within, or
in the immediate vicinity of, their household,
workplace and educational or health institutions.
• Relatively small adjustments to water and
sanitation services can ensure that the needs of the
disabled, elderly, women and children are not
overlooked, thus improving the dignity, health,
and overall quality for all.
• According to WHO, the water source has to be
within 1,000 metres of the home and collection
time should not exceed 30 minutes.

Cont’d
• The average distance that women in Africa and Asia
walk to collect water is 6 kilometres. United Nations,
OHCHR, UN-Habitat, WHO. (The) Right to Water, Fact
Sheet No. 35. 2010
• Inadequate sanitation, poor hygiene and unsafe
drinking water contribute to 88% of diarrhoeal disease.
WHO, Global Health Risks: Mortality and Burden of
Disease Attributable to Selected Major Risks. 2009
• Accessible drinking water can help avoid potentially
risky methods of water storage and gathering. For
instance, India witnessed a severe outbreak of dengue
fever when people stored water in their homes for use
through dry spells, thus providing ideal habitats for
Aedes mosquitoes. WHO, The right to water. 2003

Affordable
• Water and sanitation facilities and services must
be available and affordable for everyone, even the
poorest.
• The costs for water and sanitation services should
not exceed 5% of a household’s income, meaning
services must not affect peoples’ capacity to
acquire other essential goods and services,
including food, housing, health services and
education.
• Almost two in three people lacking access to
clean water survive on less than $2 a day, with
one in three living on less than $1 a day.

Cont’d
• People living in the slums of Jakarta, Manila and
Nairobi pay 5 to 10 times more for water than
those living in high-income areas in those same
cities and more than consumers in London or
New York.
• In Manila the cost of connecting to the utility
represents about three months’ income for the
poorest 20% of households, rising to six months’
in urban Kenya. UNDP. Human Development
Report 2006. Beyond Scarcity: Power, poverty
and the global water crisis. 2006

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