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Fundamental properties of
water and Methods of
Purification
Presented by:
Becky Lacey
Water purification specialist
Content
History of Water
Where it comes from
Impurities
Variations around the
country
ƒ Methods of water
purification
ƒ Summary
ƒ Useful terminology
ƒ
ƒ
ƒ
ƒ
History of Water
• The Indus Civilisation, which produced the
first cities around 2500BC, also built the
first sewers. They even had man hole
covers so they could be cleaned and
unblocked
• Jerusalem in the 7th Century BC was
supplied by a man-made underground
water tunnel which led from a protected
spring outside the walls
History of Water
• The Roman Empire was famous for
building aqueducts to bring water to its
cities. Everyday the people of Rome used
more than 1000 million litres of water for
all uses including fountains and baths.
Few homes had piped water though.
People carried their waste to sewage
disposal points, which led to the Greater
sewer or Cloaca Maxima
History of Water
• The Inca Empire provided homes for about
12 million people. To keep people healthy
a stone channel ran down each street in
the main city carrying fresh water from the
mountains, ready to flush away sewage
• The Ashanti Kingdom in 18th century West
Africa was very clean. Buildings in the
capital had sewage pipes cleaned on a
daily basis with boiling water and remote
villages had public toilets
History of Water
In the UK
•
•
•
1300 – 1600 – Lead pipes were laid, various methods employed to
transport water to cities and towns around the country. By the end of
the 1500’s filtration water started to take place.
1600 – 1800 – The first flushing toilets were designed and
introduced.
1800 – 1900 – Mechanical and sand filtration were perfected. 1847 it
was a criminal offence to pollute drinking water. 1852 The General
Board of Health recommended new sewers in every town. Between
1832 – 1847 there were Cholera Epidemics which lead to 1858 –
The year of the “Great Stink” seeing the recommendation of 1852
carried out. 1885 water was checked fro bacteria for the first time.
Reservoirs were built around the country.
History of Water
In the UK
•
1900 – present day The routine way to treat water was to: Screen
to catch branches, solids and dead animals, treat it with aluminium
sulphate to remove solids and chlorinate against bacteria. 1945 the
Water Act reorganised the water industry. 1973 the water bill for
England and Wales created 10 Regional Water Authorities. 1989
The Water Act allowed local authorities to sell off the water
companies
Water Companies
•
•
•
•
•
•
•
•
Anglian Water
Bournemouth and West
Hampshire Water
Hampshire Water
Bristol Water
Cambridge Water
Cholderton and District Water
Dee Valley Water
Dwr Cymru (Welsh Water)
•
•
•
•
•
•
•
•
Essex and Suffolk Water
Folkstone and Dover Water
Mid Kent Water
Northumbrian Water
Portsmouth Water
Scottish Water
Severn Trent Water
South Staffordshire Water
South East Water
Definition of water
The chemical symbol for water is H2O
Definition of water
The chemical symbol for water is H2O
As a chemical it is defined as Dihydrogen Oxide and
therefore it is a binary compound that occurs at room
temperature as a clear, colourless, odourless liquid.
Dihydrogen Oxide freezes at 0°C and boils at 100 °C
At atmospheric temperatures and pressures it can exist in
all three of it’s phases:
Solid (Ice)
Liquid (Water)
Gaseous (Water vapour / steam)
The Water Cycle
1 = Precipitation
2 = Condensation
3 = Transpiration
4 = Evaporation
5 = Surface run off
Impurities of Water
• In solution
• In suspension
• Gases
Impurities in Solution
An Inorganic compound is any
substance in which two or more chemical
elements other than carbon are combined.
Picture = Calcium carbonate crystals
Organic compound are substances
whose molecules contain one or
more (often many more) carbon
atoms
Impurities in Suspension
Colloids are substances inorganic
or organic which are finely dispersed
throughout the liquid medium of
water.
Particle size is usually between 1100nm.
Living matter which will include any plant,
animal or bacteria
Gases
Carbon Dioxide - CO2
Oxygen - O2
Sulphur Dioxide – SO2
Chlorine – Cl2
Water Sources for England
and Wales
Prescribed Concentration
or Value (PCV)
Substance
Standard
Microbiological parameters
Amount Allowed
Faecal coliforms, faecal streptococci,
Clostridium perfringens
0 per 100 ml
Substance
Standard
Amount Allowed
Chloride
400 mg/l
Chlorine
No standard
Chromium
50 µg/l
Colour
20 mg/lPt/Co scale
Total coliforms
0 per 100 ml
Chemical parameters
Amount Allowed
Alkalinity
No standard
Conductivity
1500 µS/cm
Aluminium
200 µg/l
Copper
3000 µg/l
Ammonium
0.5 mg/l
Cyanide
50 µg/l
Antimony
10 µg/l
Fluoride
1500 µg/l
Arsenic
50 µg/l
Iron
200 µg/l
Barium
1000 µg/l
Lead
50 µg/l
Boron
2000 µg/l
Magnesium
50 mg/l
Cadmium
5 µg/l
Manganese
50 µg/l
Mercury
1 µg/l
Nickel
50 µg/l
Calcium
250 mg/l
Prescribed Concentration or
Value (PCV)
Substance
Standard
Substance
Amount Allowed
Nitrate
50 mg/l
Nitrite
0.1 mg/l
Oxidisability
5 mg/l
PAH
0.2 µg/l
Benzo3,4 pyrene (a PAH)
10 ng/l
Pesticides
Standard
Amount Allowed
Sulphate
250 mg/l
Surfactants
200 µg/l
Temperature
25 C
Tetrachloroethene
10 µg/l
0.1 µg/l
Tetrachloromethane
3 µg/l
PH
5.5-9.5
Trichlorethene
30 µg/l
Phosphorus
2200 µg/l
Trihalomethanes (THMs)
100 µg/l
Potassium
12 mg/l
Turbidity
4 Formazin Turbidity Units
Qualitative odour and taste
No standard
Total dried solids
1500 mg/l
Quantitative odour and taste
Dilution No of 3 at 25ºC
Total hardness
No standard
Selenium
10 µg/l
No significant increase
Silver
10 µg/l
Total organic carbon
(TOC)
Sodium
150 mg/l
Zinc
5000 µg/l
Definition of water
ƒ
ƒ
ƒ
ƒ
ƒ
ƒ
Conductivity (μS/cm)
Total Dissolved Solids (TDS) (ppm or mg/l)
Resistivity (MΩ-cm)
pH
Hardness
Fouling Index (silt density)
Purification Technologies
Distillation
ƒHeat water to boiling
ƒCondense water vapour
ƒCollect condensate(liquid)
In separate container
Purification Technologies
Ion – Exchange (DeI)
ƒChemical exchange process
ƒWorks only with elements
in a charged state
ƒOnce exhausted can be regenerated
ƒInstantaneous demand
ƒGood food source for bacteria
Purification Technologies
Reverse Osmosis (RO)
ƒSophisticated filtration
ƒPhysical removal
ƒRequires pressure
ƒ93-98% removal of minerals
ƒ99% Bacteria
Purification Technologies
Filtration
ƒPhysical removal based
on particle size
ƒRemoval of particles
ƒ0.2µm filter size removes
bacteria (ultra – microfilters)
ƒ0.1 – 0.01µm filter size
removes endotoxin (ultra-filtration)
Purification Technologies
Ultra violet irradiation (UV)
ƒShort wavelength energy
ƒBreaks C-C bonds
ƒ185nm - Small chain organic molecules
ƒ254nm - Bacteria
Purification Technologies
Organic Adsorbtion
ƒConcentration of organic molecules at
the surface of usually activated carbon
media sometimes man made resins
ƒLow molecular weight organics
ƒ185nm - Small chain organic molecules
ƒ254nm - Bacteria
Technologies
Distillation
Resistivity
Conductivity
Hardness
Heavy Metals
Silica
pH
Total Organic
Carbon
Micro-organisms
Endotoxins
Particles / colloids
Reverse
Osmosis
Deionisation
Organic
Adsorbtion
Filtration
Ultrafiltration
UV
Market sector
Parameter
Clean Steam
Micro
Electronics
<35
_
_
18.2
TDS (ppm)
30
_
Hardness (ppm)
_
_
0.1
0.05
_
5
_
0.05 - 1
Renal
Conductivity (µS-cm)
USP
Pharma
Laboratory
Clinical
<1.29
Resistivity (MW/cm)
1 to 10
Heavy Metals (ppm)
1 to 10
0.1
TOC (ppb)
<500
<50
<50
Particles (µm)
Chlorine/Chloramines (mg/l)
<0.1
0.01
Calcium (mg/l)
<2
0.005
Nitrate/nitrite (mg/l)
<2
0.2
0.01
<0.01
0.01
0.005
Aluminium (mg/l)
Silica (ppb)
Bacteria (cfu/100ml)
<100
<100/ml no
P
aeruginosa
or E Coli
Endotoxins (Eu/ml)
<0.03
<0.25
<100
depends
50
10
3
<10/ml
_
1
0.25
0.03
Quotations for Water
If there is magic on the planet, it is contained in the water.
- Loren Eisley
When the well is dry, we know the worth of water.
- Benjamin Franklin
Thank you for your
attention
Useful Terminology
• Potable water
– Water suitable for drinking
• Hardness
– The scale - forming and lathering inhibiting qualities which
some water supplies possess caused by high concentrations of
calcium and magnesium
• Conductivity
– The process of electrical transfer through water, measured in
microsiemens/cm.
• Resistivity
– The reciprocal of conductivity. Resistivity is usually corrected to
25 degrees centigrade and expressed as megohm-cm.
1megohm-cm is equivalent to 1 microsiemen/cm
Useful Terminology
• pH
– A measure of the acidity or alkalinity of a solution. pH1 is very
acid pH7 is neutral and pH14 is very basic. pH is measured
using a glass electrode.
• OA
– Oxygen Absorbed is a measure of organic content of water.
The water is reacted with acidified potassium permanganate
and the permanganate consumed is used to quantify the
organics present with the result being expressed in ppm O2
• SDI
– Silt Density Index, also called Fouling Index (FI), a test used to
estimate the concentration of colloids in water; derived from the
rate of blockage of a 0.45 micron filter
Useful Terminology
• Bacteria
– Also known as Microorganisms are some of the simplest living
cells known usually found as single cells living “alone” or in
groups as chains or clumps of cells. Cell size varies from 0.5 10 micron.
• Colloid
– A stable dispersion of fine particles in water that have a typical
size less than 0.1 micron. Colloids containing iron (Fe),
aluminium (Al), silica (SiO2) and organics are commonly found
in water.
• Total Dissolved Solids
– A measure of the total of organic and inorganic salts dissolved
in water, obtained by drying residue at 180ºC.
• PPM
– parts per million is a unit equal to milligram per kilogram of
water, ppm is equivalent to mg/l in dilute solutions.
Useful Terminology
• Ion
– Any non aggregated particle of less than colloidal size
possessing either a positive or a negative electric charge.
Some organic molecules are so large that even as ions they
are considered to be colloids.
• Cation
– A positively charged ion
• Anion
– A negatively charged ion
• Molecule
– The smallest particle of an element or compound that is
capable of separate existence without losing the properties of
the substance.