Water Quality Standards

WATER QUALITY
okellojimmy1919@gmail.com
0782207941
1
Okello Jimmy
PGDME(MUK),MPH(GULU) BEHS
(MUK), DHLM(UAHIMS)Cert. EHS
(UAHMS-Mulago)

DEFINITIONS
“Water quality” is a measure of organisms,
minerals, and organic compounds contained
in water.
 Potable water is water suitable for drinking
and cooking purposes.
Potability considers both the safety of water
in terms of health, and its acceptability to
the consumer – usually in terms of taste,
odor, color, and other sensible qualities.
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Classes of drinking water
• Class I: This is potable water available
from conventional treatment processes
such as;
– chlorination,
– filtration, and
– ozonation and used in food establishments
or distributed through the water distribution
systems.
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Water classes cont’d
• Class II: This is potable water available for
water consumers through;
– boreholes,
– protected springs,
– shallow wells,
– gravity flow schemes and
– harvested rain water which may be used for
consumption in accordance to set guidelines.
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Water basic requirements
• Drinking water should be;
– Free from pathogenic (disease causing)
organisms;
– Clear (low turbidity, little colour),
– Not saline (salty);
– Free from offensive taste or smell;
– Free from compounds that may have had
adverse effects on human health (harmful in the
short or long term);
– Free from chemicals that may cause corrosion
or encrustation.
– Incapable of staining clothes washed in it
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Components of water quality
• In accordance with the Uganda National
Standards for Drinking Water, there are three
aspects of water quality;
– Chemical,
– Physical and
– Microbiological aspects
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Physical aspects
The common physical aspects that should
be monitored include;
– The turbidity,
– color,
– taste, and
– odor of water.
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Turbidity
• Turbidity refers to the cloudiness of the water.
• It can be a problem in surface water sources.
• The materials causing the cloudiness can be
inorganic (such as clays, silts, or sand) or
organic, such as algae and leaf particles.
• Turbidity of drinking water is important for a
number of reasons.
The turbidity in the water may shield bacteria,
preventing disinfection chemicals from attacking
and destroying the cells.

Turbidity cont’d
Another health concern relates to organic
materials that cause turbidity in the water.
• These materials, in conjunction with chlorine, can form
trihalomethanes and other potentially harmful
chemicals.
• From an aesthetic standpoint, turbidity in the
water makes it less appealing to many people.
• Most operators have had to field complaints
about bubbles and cloudiness in the water,
which may be caused, not by turbidity, but by
the aerator on faucets in the home.

Turbidity cont’d
• Turbidity is normally tested using instruments
that pass a light through the water and measure
the light refraction at a 90-degree angle from the
light source.
This may be done by process meters that continuously
measure the water in line, or by using meters in the
lab for grab samples.
Most meters used today are of the Nephelometric
type.
They are calibrated by using formazin standards
supplied with the meters.
Turbidity is expressed in Nephelometric Turbidity Unit
(NTU) units.

Turbidity
• Turbidity should always be low, especially
where disinfection is practiced.
• High turbidity can;
inhibit the effects of disinfection against
microorganisms and
enable bacterial growth.
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Turbidity determination
• Procedure
o Draw water in a clear glass
o Hold it to stand for 30 minutes
o Note the settled matter if any
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Colour
• Color – is due to the presence of colored
substances in solution, such as;
o vegetable matter and
o iron salt.
• It does not necessarily have detrimental
effects on health.
• Color intensity could be measured through
visual comparison of the sample to distilled
water.
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Odour
• Odour is sensation that is due to;
• the presence of substances having
appreciable vapor pressure and
• that stimulate the human sensory organs in
the nasal and sinus cavity
• Odor – odor should be absent or very
faint for water to be acceptable for
drinking.
• Pure water is odorless;
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Odour
• Presence of undesirable odor in water is
indicative of the existence of contaminants like;
o Organic matter
o Biological activity and
o Industrial pollution
• These contaminants originate from;
o Presence of hydrogen sulphide (from specific
sewage biological reduction of sulphate)
o Organic matter from sewage, septic tanks, pit
latrines
o Growth of algae, protozoa and fungi
o Industrial chemicals
o Contact with painted surfaces like bitumenous lining
on tanks okellojimmy1919@gmail.com
0782207941
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Odour determination
• Procedure
o Take representative sample and put it in a clear
bottle (don’t fill to brim)
o Cork the bottle tight
o Vigorously shake for 10-20 seconds
o Uncork and smell
 Note the temperature at which the test is being done
o To confirm, heat the water in a bath to 60oC
o Shake again, open and smell
 Pure water does not smell
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Taste
• Taste is the sensation from interaction of
the taste sensory organs and substances
• Pure water is tasteless
• Presence of undesirable taste in water
indicates presence of contaminants.
• Substances/contaminants that cause tastes
include;
o Algae,
o decomposing organic matter,
o dissolved gases, and
o phenolic substance.
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Taste determination
• Difficult to determine and depends on
temperature
o The cooler the water, the pleasant the taste
 E.g. at 0-20oC taste mechanism is desensitized
enough not to detect salt in water
• It is advisable that water taste is only
tested for safety for drinking by;
o Bacteriological and
o Chemical tests
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Taste determination cont’n
• Alternative taste test due to salinity by
iron and manganese compounds is by;
o boiling water and adding tea leaves
 If the tea turns black , it shows the presence of
salts of the two compounds
• Common tastes
o Taste tests are done by panel of judges but
best done by consumers
 Salty – high in chlorides and sodium salts
 Bitter – magnesium sulphate
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Taste determination cont’n
• Common tastes
Sweet – organic matter
Metallic – iron, manganese
Sharpness – chalk, calcium carbonate and
carbondioxide
Flat – some surface source, less oxygen, long
stagnation in dead end mains or cisterns
Musty (stale) – fungi, water being heated in
transmission system especially in tall
buildings
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Characteris
tic
Units Class I Class II
Colour TCU (True colour
Units)
15 15
Odour TON (Threshold
Odor Number)
Acceptable to
consumers &
no abnormal
changes
Acceptable to
consumers &
no abnormal
changes
Taste FTN (Threshold
Flavor Number)
Acceptable to
consumers &
no abnormal
changes
Acceptable to
consumers &
no abnormal
changes
Organoleptic and physical requirements of
water in Uganda
21

22
Characteristic Unit Class I
requirement
Class II
requirement
Turbidity NTU
(Nephelometric
Turbidity Units)
≤ 5 ≤ 10
pH 5.5-8.5 6.5-8.5
Electrical
conductivity
at 25oC
µS/cm 1500 2500

Chemical aspects
• Chemical contamination of water sources
may be due to natural sources, certain
industries and agricultural practices.
• When toxic chemicals are present in
drinking water, there is the risk that they
may cause either acute or chronic health
effects.
• Chronic health effects are more common
than acute effects because the levels of
chemicals in drinking water are seldom high
enough to cause acute health effects.
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pH value of water
• Also known as hydrogen potential
• pH value measures the level of hydrogen
ions concentration in given water.
• Expressed on a scale of 0-14
o Below 7, water is acidic
o Above 7, water is alkaline
• A change of one (1) pH means a ten-fold
increase or decrease in the hydrogen ion
concentration.
• Acidic water is corrosive to metallic pipes.
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pH value of water cont’d
• Acidity
o It is when water is < 7 on a pH scale
o Sources of acidity;
• In unpolluted water, it is attributed to carbondioxide,
a weak acid
• Organic matter decomposition
• Industrial pollution
o Wholesome water should not be corrosive
o Treatment should reduce the acidity
o Acid water corrodes pipes
• Water with a pH of 5.5 may be acting as a solvent,
dissolving lead and iron
25

• Alkalinity
o Due to bicarbonate and hydroxide ions in water
• Associated with calcium, magnesium, sodium, and
potassium
o It occurs in water below a pH of 7
• Between 4.6 and 8.2 pH occurs bicarbonate alkalinity
• Above 8.3 pH, carbondioxide ceases to exist forming
carbonate or temporary hardness
• when the value is less than total hardness, the
difference makes non carbonate permanent hardness
• Majority of water is 7-8.5 pH otherwise 6.5-9.2 pH is
acceptable
26

• Alkalinity
o High concentration of sodium carbonate
gives a bad taste
o Alkalinity is important in determining
coagulation with water of low pH
o Excess lime in softening can cause alkalinity.
• This can be neutralized by chlorination
27

Determination of pH
• The pH is normally measured by use of pH
comparator.
• Procedure
o Measure 10cc of water sample into a test tube
o Add 0.1ml of solution of phenol red
o Neutralize with sodium thiosulphate in case of
chlorinated water
o Place the tube in a lavibond comparator
o Read the comparison of the colours of
comparator matching with the tube with water
o Interpret the colour
28

Hardness
• Hardness is due primarily to;
o calcium and magnesium carbonates and
bicarbonates which are removed by boiling and
o calcium and magnesium sulphate and chloride. This
is removed by chemical precipitation using lime and
sodium carbonate.
• Acceptable value for hardness (calcium
carbonate) is 600 mg/l and
• Maximum acceptable concentration is 800 mg/l
• Hardness is due primarily to;
– calcium and magnesium carbonates and
bicarbonates removed by boiling and
29

Hardness cont’d
– calcium and magnesium sulphate and
chloride removed by chemical precipitation
using lime and sodium carbonate.
• Hardness in water is objectionable for
the following reasons:
– Calcium and magnesium sulphate have a
laxative effect.
– Hard water makes lathering more difficult.
This increases soap consumption.
– In boilers, pots and kettles, hardness causes
scaling. This results in the reduction of the
thermal efficiency and restriction of flow.
30

Dissolved oxygen
• This is a measure of quality of rivers and
lakes in relation to sustaining life
• Concentration of oxygen varies widely
depending on;
o Physical, chemical, biological and
microbiological processes
o Atmospheric pressure. Increased pressure
increases dissolved oxygen
o Temperature. Temperature increase lowers
dissolved oxygen
o Salinity or Total Dissolved Solids (TDS)
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Dissolved oxygen
– Depth of water; Underground water has a range
of 0.1% lower oxygen levels mean depletion of
oxygen due to oxidation of ozonic material as
water percolates
• Disadvantages of water devoid/reduced of
oxygen;
– Has a flat taste,
– Reduction of oxygen to below 80% causes
consumer complaints
– may indicate an appreciable level of oxygen-
consuming organic substances lie raw sewage
32

Dissolved oxygen
• High oxygen levels being high increases
corrosiveness of water to iron or brass at
acidic pH values
• Determination of dissolved oxygen;
o Estimated oxygen is got by use of two
figures;
• In 15 min at 80oF
• In 4 hours at 80oF
33

Determining dissolved oxygen
• Procedure;
Sample and warm 250mls of water to 80oF
Add 10ml potassium permanganate
Add 10ml dilute hydrochloric acid
Incubate for 4 hours
The quantity of oxygen can be calculated by
determining the amount of oxygen absorbed
termed as B.O.D
34

Chemical Oxygen Demand (COD)
• COD is a measure of the amount of
organic content of water.
• As bacteria utilize oxygen in the oxidation
of organic matter;
o the COD increases and
o the dissolved oxygen in the water decreases.
35

Toxic substances
• A number of chemical substances, if
present in appreciable concentration in
drinking water, may constitute a danger
to health.
• These substances include; arsenic,
barium, cadmium, hexavalent chromium,
cyanide, lead, selenium and silver.
36

Iron and manganese
• Groundwater usually contains more of
these two minerals than surface water.
• Iron and manganese are nuisances that
must be removed if in excess of 0.3 mg/l
and 0.1 mg/l respectively.
o They stain clothing and plumbing fixtures,
and
o the growth of iron bacteria causes strainers
and screens to clog and metallic conduits to
rust.
37

Iron and Manganese
• Procedure;
o Obtain a sample of water
o Shake the water
o Observe the precipitates formed
• The appearance of a reddish brown precipitate
indicates presence of iron and
• black precipitate in a water sample indicates
presence of manganese.
38

Carbondioxide
• Carbon Dioxide is dissolved from the
atmosphere as it rains
• Underground free carbondioxide may reach
100mg/l concentration
• It is regarded as good for digestion often
referred to as mineral water
• The presence of appreciable quantities of
carbon dioxide makes water corrosive due
to carbonic acid formation and the presence
of free CO2
o This corrodes iron pipes and causes cavitation in
pipes
39

Organic Nitrogen
• Organic Nitrogen is a constituent of all waste
protein products from sewage, kitchen wastes
and all dead organic matter.
• Freshly produced waste normally contains
pathogenic bacteria.
• All water high in organic nitrogen should
therefore be suspected for possible contaminants
• The commonest nitrogenous compounds are;
o Nitrites
o Nitrates
o Ammonium nitrogen
o Albumoid ammonia
40

Organic nitrogen cont’d
• Nitrites
o In water, it indicates sewage or other organic
matter undergoing oxidation process
o Water regarded as fit for domestic purpose
when nitrite value is zero
o In some appropriate case, acceptable figure
is 0.1 ppm
o In Uganda, recommended level is 0 (zero)
o Nitrites are corrosion inhibitors
o Used in preservation in the meat industry
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• Nitrates
– It’s presence in water indicates the final
stages of decomposition (oxidation) of
organic matter
– Also indicates water from wells that
penetrate strata known to be rich in nitrates
– The mpl should be 0.03ppm
• Ammonium nitrogen
o This is free and saline ammonia
o Ammonia and ammonium salts in solution
indicate decomposing organic matter.
42

o The maximum permissible levels (mpl) is 0.08ppm
• Albumoid ammonia
o Its presence indicates nitrogenous
substances decomposing in water
• Organic acid nitrogenous substances are set free
during decomposition of organic matter
43

Chlorine as chlorides
• May be naturally occurring such as NaCl, KCl
and CaCl2 present in sea and ocean
• Origin could be;
– Dissolution of salt deposits
– Discharges of effluents in chemical industries
– Contamination resulting from salting rod to melt
ice and snow
– Sea water intrusion
– Refuse leachates
44

Chlorine as chlorides
• Chlorine affects surface and underground
water.
• It is responsible for;
– Osmotic process in the body
– Water electrolyte balance
– Taste in water
– Acidity of water hence corrosion
– Cold and hot water supply LDL 250mg/l or
600ppm as HDL
45

Chemical requirements for water
Characteristic Units Class I
requirement
Class II
requirement
Total Dissolved
Solids (TDS)
Mg/l 500 1500
Iron Mg/l 0.2 1
Ammonia Mg/l 0.5 1
Aluminium Mg/l 0.2 0.2
Potassium as K Mg/l 50 (max) 100 (max)
Sodium as Na Mg/l 200 (max) 400 (max)
Chloride Mg/l 250 500
Magnesium Mg/l 100 150
46

Requirements for naturally occurring chemicals
Characteristic Units Class I
requirement
Class II
requirement
Arsenic Mg/l 0.01 0.05
Barium Mg/l 0.7 1.0
Boron Mg/l 1.0
Chromium Mg/l 0.05 0.05
Flouride Mg/l 1.0 1.5
Manganese Mg/l 1.0 0.1
Molybdenum Mg/l 0.07
Selenium Mg/l 0.01 0.01
Uranium Mg/l 0.015 0.015
Mercury Mg/l 0.001 0.001
47

Dissolved solids
• The total dissolved solids can have a
significant impact on the quality of water.
• The amount of dissolved solids affects the
water for almost all of its uses, whether for
drinking, agricultural, or industrial use.
• The recommended maximum limit of
dissolved solids in drinking water is 500 ppm.

Dissolved solids cont’d
• The problems caused by dissolved material
relate to taste and odor, hardness, and
corrosion and scaling in the distribution
system, among others.
• Several different types of dissolved solids
could be toxic if the levels become too high.
– These include barium, arsenic, cadmium,
chromium, lead, mercury, selenium, and silver.
– Each of these is regulated by the Environmental
Protection Agency (EPA) and has maximum
contaminant levels assigned to them.

Organics
• Organic material can cause problems in terms
of health effects, treatment and taste, odor,
and color of water.
• Some organics are potential carcinogens; that
is, they may cause cancer.
• Cancer-causing substances may be formed
when naturally occurring organic material
formed by plant and animal decomposition
combines with chlorine, forming
trihalomethanes.

Organics cont’d
• Others may already be present in the raw surface
or groundwater as a result of contamination of
the water source.
• Some major sources of organic contamination are
pesticides, herbicides, domestic waste, and
industrial waste.
i. Algae
Algae (one-celled, microscopic, and larger) aquatic
plants,
some microscopic, can be quite abundant in a surface
water source, especially during the warm months and

Organics cont’d
especially if the water contains nutrients that
encourage their growth, such as phosphorus from
domestic run-off or industrial pollution.
Algae may cause taste and odor problems, clog filters,
and produce nuisance slime growths on intake pipes
and equipment.
ii. Bacteria
– Bacteria are microscopic one-celled organisms that
multiple by simple division. Bacteria are universally
distributed.
– Many of them are essential. For example, they aid in
the decomposition of dead organic material.

Organics cont’d
– However, there are numerous disease-producing
bacteria that the water industry needs to guard
against.
– These may cause typhoid fever, dysentery, cholera,
and gastroenteritis.
– Some bacteria, although not harmful, may cause taste
and odor problems.
• Examples of such bacteria are sulfur bacteria, which may
produce hydrogen sulfide, or
• crenothrix iron bacteria which can produce disagreeable
taste, odors, and stains.
– Disease-causing bacteria are called pathogenic
bacteria.
– It is often hard to test for and identify them.

Organics cont’d
– Therefore, their presence is determined by testing for
the presence of an indicator organism, usually
coliform bacteria.
– This group of bacteria is found in the intestines of
warm-blooded animals; it is also common in soil.
– A more specific group of bacteria are the fecal
coliforms, which are directly associated with
contamination from human or animal wastes.
– Presence of coliform bacteria indicates general
bacterial contamination.
– The presence of fecal coliform indicates
contamination from a human or animal source.

Organics cont’d
iii. Protozoans
– Protozoans are single celled, usually microscopic,
organisms.
– Some protozoans, such as Giardia and
Cryptosporidium, are commonly found in rivers, lakes,
and streams contaminated with animal feces or which
receive wastewater from sewage treatment plants.
– When a water system uses surface water as its source,
Giardia and Cryptosporidium must be removed in the
clarification process because they are very difficult to
kill with the usual forms of disinfection.

Organics cont’d
– If a person is infected, the symptoms may last
seven or more days and include diarrhea, stomach
cramps, nausea, fatigue, dehydration, and
headaches.
– Protozoans are very difficult to test for;
– 100 or more gallons of water must be piped
through a filter with openings less than one
micron in size at 1 gpm or less.
– The particles trapped by the filter are then
analyzed using very sophisticated methods to
determine if any protozoa are present.

Organics cont’d
iv. Viruses
Viruses are the smallest living organisms
capable of producing infection and causing
disease.
Viruses that may be carried by water
include the hepatitis and polio virus.
They are very difficult to test for; usually
large amounts of water have to be tested by
using very sophisticated methods.

Radionuclides
• Radiological contaminants emit radioactivity as
they decompose.
• Sources of radioactive material are likely the
aquifer minerals the water moves through.
• Radium 226, radium 228, uranium, and radon are
the most common radioactive elements are most
common.
• Radiological elements tend to be a greater
problem in groundwater than in surface water,
and radon may be elevated in groundwater that
has been in contact with granite.

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