Module 1_water Impurities
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Transcript of Module 1_water Impurities
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Module 1: Water Impurities
Course Teacher
Dr Muhammad Azizul HoqueAssociate Professor
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Sources of water/water quality
Water is a solvent
Source Quality
Rainwater natural distillation
Air quality + catchment
Surface water The above + pollutantsspecific to the catchment
Groundwater Rainwater characteristics+geological formation+minerals
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Potable Reuse (Unplanned)
Water Treatment
City A
Wastewater
Treatment
Water Treatment
City BWastewater
Treatment
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Important water-borne poisons
Toxic substances from mineral formations such as fluorine,selenium, arsenic, boron etc.
Phytotoxin produced by specific algae
Heavy metals from water-works structure, metallic pipes, industrialeffluents such as lead, copper, chromium, mercury, cadmium etc.
Poisonous compounds contained in industrial and householdwastes and wastewater discharged into water courses
Residues of pesticides and insecticides reaching water coursesfrom chemical dust and sprays applied to crops, land, and watersurfaces fro the control of pests,, nuisance insects, vectors ofdiseases, weeds etc.
Radioactive substances reaching water bodies
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Impurities of water
Impurities of mineral origin
Impurities organic origin
Living impurities
Radioactive impurities
Four categories:
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Effect of impurities present in water
Source: ITN-Bangladesh
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Water quality parameters
pH, Color, Turbidity, Total dissolved solids (TDS), Alkalinity,
Hardness, Chloride, Nitrate, Iron, Sodium, Total coliform and faecal
coliform, Arsenic, Boron, Chromium, Cadmium, Copper, Lead,
Nickel, Zinc
Go through: Source, Measuring unit and Significance of water
quality parameters
# Physical # Chemical # Bacteriological # Radiological
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Solids
SampleSettleable
solids TotalSolids
Filter
(glass fibre)
EvaporationEvaporation
Dissolved
SolidsSuspended
solids
Furnace (550C)
TS
Total
Fixed Solids
Total volatile
Solids
Fixed SSVolatileSuspended solids
VolatileDissolved Solids
Fixed filterablesolids
Furnace (550C)
Imhoff
cone Evaporation
Filtrate
SampleSettleable
solids TotalSolids
Filter
(glass fibre)
EvaporationEvaporation
Dissolved
SolidsSuspended
solids
Furnace (5500C)
TS
Total
Fixed Solids
Total volatile
Solids
Fixed SSVolatileSuspended solids
VolatileDissolved Solids
Fixed filterablesolids
Furnace (5500C)
Imhoff
cone Evaporation
Filtrate
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Total Dissolved Solids
Soluble inorganic salts
Cations of Ca, Na, Mg, K
Anions of Cl-, HCO3- and NO3
-
Need to filter using 0.45 micrometer
Drinking water can be treated Excellentwhen TDS < 300 mg/L
TDS >1200 mg/L is Unacceptable
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Hardness
Presence of polyvalent (but not singly charged)metallic cations.
Most polyvalent are divalent Ca and Mg
expressed as the sum of concentrations of these
elements (mg/L as CaCO3) Principal anions and cations indicating hardness
Cations Anions
Ca++ HCO3-
Mg++ SO42-
Sr++ Cl-
Fe++ NO3-
Mn++ SiO3-
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Total Hardness
Temporary hardness (Carbonate hardness)
Solution of Ca and Mg with bicarbonate in water
Removed by boiling water containing HCO3- can be
heated to precipitate (CO32-) as scale
Permanent hardness (Noncarbonate hardness)
Caused by Ca and Mg compounds of sulfates, chlorides
or silicates
Cannot be removed by boiling, but precipitation
softening process or ion exchange using selective ions
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Problems with hardness
Hard water (>200 mg/l as CaCO3)
Reduction in cleaning action of soap
Scale formation in boilers, water systems and heat
exchangers
Soft water (
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Alkalinity
Measure of the ability of a water to neutralize theacids. (absorb H+ ions without significant pHchange)
The principal alkaline ions are OH-, CO32- and
HCO3- and usually expressed in terms of CaCO3
Important during coagulation
Depending on pH, alkaline samples can containOH- alone, OH-+ CO3
2-, CO32-alone, CO3
2- andHCO3
- or HCO3- alone.
pH>10, OH- or OH- and CO32-(No significant OH- existbelow this pH)
pH>8.3 CO32- and HCO3
- (No significant CO32- exist
below this pH)
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Hardness and Alkalinity
Hardness by multi-positive ions and alkalinity by
negative ions
Alkaline water can be hard If hardness and alkalinity are same, then there
are no SO42-, Cl- or NO3
- (no non-carbonate
hardness)
If hardness > alkalinity, non carbonate hardnessis present and carbonate hardness = alkalinity
If hardness < alkalinity, all hardness is carbonate
hardness and extra HCO3- comes from other
sources such as NaHCO3
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Radiological (uranium and thorium ) Radioactivity
is the energy released from the breakdown ofradionuclides
Naturally occurring radioactive species in drinking water
sources
Contamination from concentration of natural levels such as
mining and processing of minerals
Artific ial radionuclides which may enter drinking water
supplies from medical and industrial use of radioactivematerials
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Pathogenic Bacteria and viruses
Bacterial water borne diseases (bacteria 0.5-5
micrometer)
Cholera, Typhoid fever, Gastro-enteritis
Viral diseases (Viruses 20 -100 nm)
Smallpox, influenza, diarrhoea, polio and hepatitis
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Indicator Microorganisms for Drinking
Water
Coliform group of microorganisms is present in large
numbers in animal and human excreta. Why is there a need
for such indicators?
Pathogenic microorganisms are small in numbers
Routine testing is not practicable and expensive
Involves skilled labour and specialist equipment
Time-consuming
Specific tests may not be available
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Indicator Microorganisms Properties
Always present when pathogens of like or igin are present
Present in large numbers, >> pathogens
Easy and quick to detect
Equal or greater survival time than pathogens
Absent from unpolluted waters
Similar sensitivity to disinfection as pathogens
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Basic requirements of Drinking water
Should be completely free of pathogenic micro-organisms that can
cause disease
Should contain no element or compound in concentrations that cancause acute or long-term adverse effect on human health
Should be fairly clear and aesthetically attractive, i.e. low turbidity
and color
Should not be saline to cause salty taste
Should contain no compounds that can cause an offensive taste
and odouor
Should not cause corrosion, scale formation, discoloration or
staining
Should not have a temperature unacceptable to the consumers
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Drinking water standardsSource: ITN-Bangladesh