A consumer’s guide to drinking water
December 2006
Prepared by the Cooperative Research Centre for Water Quality and Treatment
Australia’s national drinking water research centre
This consumer's guide to drinking water outlines all aspects of drinking water from the catchment to the tap.
It provides an overview of water in Australia and around the world and
discusses how water is collected, treated, distributed, used and regulated.
The Australian Drinking Water Guidelines are referred to at various points
throughout this website. The Australian Drinking Water Guidelines define good
quality drinking water and help Australian water authorities provide good
quality drinking water to consumers.
For more information on technical aspects of drinking water quality, examine
the Australian Drinking Water Guidelines
(http://www.nhmrc.gov.au/publications/synopses/eh19syn.htm)
This guide has been created in PDF format to reproduce the hyperlinked structure of the Web page
version and allow the guide to be used without an internet connection. Users who choose to print the
document for reference should note that the Appendix 1, which follows the Glossary, contains more
detailed information on specific topics mentioned in the main text.
1
TABLE OF CONTENTS
SOME FACTS ABOUT WATER .............................................................................................3
ABOUT WATER AND AUSTRALIA .....................................................................................5
WHO USES WHAT? ................................................................................................................9
THE WATER CYCLE ............................................................................................................14
URBAN WATER SYSTEMS .................................................................................................16
WHAT IS DRINKING WATER? ...........................................................................................21
WHAT ABOUT BOTTLED WATER?...................................................................................22
WHY TREAT WATER? .........................................................................................................23
HOW IS WATER TREATED? ...............................................................................................26
IS A WATER FILTER NECESSARY? ..................................................................................39
DELIVERING WATER TO THE COMMUNITY.................................................................40
WATER AND HUMAN HEALTH.........................................................................................45
WATER REGULATIONS, GUIDELINES AND STANDARDS..........................................54
ASSURING QUALITY...........................................................................................................55
WATER AND PUBLIC POLICY ...........................................................................................57
WATER IN THE FUTURE.....................................................................................................64
GLOSSARY OF WATER-RELATED TERMS .....................................................................68
APPENDIX 1...........................................................................................................................81
2
SOME FACTS ABOUT WATER
More than 70 per cent of the Earth’s surface is covered by water. The oceans
and seas contain 97 per cent of all the water on the planet. Less than three per
cent of the Earth’s water resources can be described as freshwater. About 77 per
cent of this freshwater is ice, mostly in the polar regions. Most of the rest is
groundwater.
Freshwater Resources as a Proportion of the
Earth's Water
Freshwater
3%
Saline 97%
It is estimated that only 0.6 per cent of the Earth’s water is readily available as a
source of water supply to its six billion people and the urban communities they
form. Water is a precious resource and, for many communities, a scarce one.
Water is essential for all living things. Plants and animals are made up of
between 50 per cent and 90 per cent water.
This amazing compound of hydrogen and oxygen is sometimes called the
universal solvent because of its ability to dissolve substances.
3
In its purest state, water is colourless, odourless and tasteless. However, water
collected from the environment naturally contains trace quantities of dissolved
and suspended materials of mineral, plant and even animal origin, which may
create colour, odour and taste.
Water collected from the environment is also likely to contain a diverse
population of microorganisms. These may or may not be a risk to human
health.
4
ABOUT WATER AND AUSTRALIA
Nothing has had a greater impact on Australia than water. Water has moulded
its ancient landscape and influenced the pattern of human habitation from
earliest times until the present. It will continue to influence people’s lifestyle,
prosperity and their relationship with the land.
Australia is a continent of extremes: of geography, climate, population
distribution and water resources. It is the driest inhabited continent on Earth,
with highly variable rainfall patterns. This variability means that Australian
communities frequently face water supply and water quality problems.
… a sunburnt country … of droughts and flooding rains ...
Scientists are now able to explain the reasons for these highly variable rainfall
patterns and even to predict weather patterns across the continent.
Why is Australia’s rainfall so variable?
The water sources available to any Australian community may include surface
water – rainfall and the resulting runoff into streams and rivers – and
groundwater – water from underground sources.
Only 12 per cent of the annual rainfall over Australia results in runoff into
streams and rivers or soaks into and is retained in the ground. The rest is
returned to the atmosphere directly by evaporation or from vegetation through
the process of transpiration.
5
Fate of Rainfall over Australia
Runoff
12%
Evaporation
and
Transpiration
88%
This results in Australia having only one per cent of the water carried by the
world’s rivers despite having five per cent of the world’s land area.
Volume
Water Carried by the World's Rivers
Australia
Africa
Europe
Asia
North
South
America America
The long term average annual rainfall over Australia is estimated to be 455
millimetres. However, this hides the very variable rainfall pattern across the
continent.
6
Location in Australia
Average Annual Rainfall (mm)
Alice Springs
270
Adelaide
500
Hobart
520
Canberra
630
Melbourne
660
Perth
790
Brisbane
1180
Sydney
1220
Darwin
1690
Depending on seasonal conditions, Australians use enough water every year to
fill Sydney Harbour almost 50 times – between 18 and 22 million megalitres of
water a year. (A megalitre is one million litres – about the volume of an
Olympic-sized swimming pool.)
According to the Australian Bureau of Statistics, about 70 per cent of this water
is used in agriculture for irrigation.
The most essential use of water is for drinking, but people drink only a tiny
fraction of the water extracted from the environment.
The environment also needs water and, with most rivers dammed or regulated,
this issue is receiving increasing attention from governments, communities and
interest groups. Examples are the “cap” on the extraction of water from the
rivers of the Murray Darling Basin, an area which includes inland regions of
Queensland, New South Wales, Victoria and South Australia, and recent plans
to restore the environmental health of the Snowy River in the east of Victoria.
To ensure a reliable water supply during periods of drought, large water
storages have been built in Australia. In fact, Australia stores more water per
head of population than anywhere else in the world. Examples of large water
storages for urban use are:
7
• Warragamba Dam, supplying Sydney, which can hold about two million
megalitres; and
• Thomson Dam, supplying Melbourne, which can hold about one million
megalitres.
Water obtained from natural sources is not pure and because of conditions in
catchments, variable rainfall patterns and other factors, the quality of water used
in the water supply is likely to vary. Frequently it requires some form of
physical and/or chemical treatment to make it safe and pleasant to drink.
Various technologies are used to remove contaminants from water and to
improve and protect water quality.
Scientists, technologists and engineers with the Cooperative Research Centre
for Water Quality and Treatment are developing new water treatment
technologies and improving existing ones. Their work will improve water
quality for many Australian communities and lower costs for Australian
households and businesses.
One particular issue affecting water quality in many areas of Australia is the
amount of salt dissolved in the water, called salinity. Salinity is now widely
recognised as one of the nation’s most devastating environmental problems.
Federal, State and Territory governments are beginning to understand the full
ramifications of the problem and are working with scientists and land managers
to slow the rate of destruction and to repair the damage where this is possible.
8
WHO USES WHAT?
In May 2000, the Australian Bureau of Statistics (ABS) produced the first
update of Australian water usage since 1985 (Water Account for Australia
1993-1994 to 1996-97). This document was part of a series developed in
accordance with agreements made at the United Nations Conference for
Environment and Development (UNCED) in Rio de Janeiro in 1992.
This publication was subsequently updated in 2004 (reflecting 2000/2001
figures) and again in 2006 to reflect figures for the year 2004/2005(Water
Account for Australia )
(http://www.abs.gov.au/Ausstats/[email protected]/0/34D00D44C3DFB51CCA2568A9
00143BDE?Open), 2004-2005, ABS Catalogue No. 4610.0). However,
comparisons with information in the earlier account must be made with caution,
owing to changes in data sources and some concepts.
In February 2001, the National Land and Water Resources Audit published the
Australian Water Resources Assessment 2000
(http://audit.ea.gov.au/ANRA/water/docs/national/Water_Contents.html) –
surface and groundwater availability and quality, the first comprehensive
national audit of Australia’s surface water and groundwater resources covering
water quantity and water quality.
Both publications provide estimates of water use in Australia and the two
relatively independent approaches corroborate each other. The latter one
indicates that groundwater use, particularly in Queensland, had been
underestimated previously.
Another relevant publication on water use in Australia is the ABS publication
Environmental Issues: People’s Views and Practices, Catalogue No. 4602.0.
This annual survey collects information on environmental behaviour and
practices of Australian households. Three survey themes rotate over three years:
water use and conservation; energy use and conservation; and waste
management and transport use. The March 2004 survey focused on water use.
The ABS data on urban water use are regarded as being the most accurate
information source and have therefore been used here.
9
In 2004/05 about 0.9 megalitres of fresh water was used for each of the 20
million Australians. This does not mean that each Australian uses this amount
each year, most use only a small fraction of that amount.
Most of this water is used for agriculture, especially irrigation, to grow food and
other commodities for consumption in Australia and for export.
Overall water consumption decreased by about 14% in 2004/05 compared to
200/01.
A topical issue for water authorities at the moment is the competing value of
water between users and the environment and, in particular, the adverse effects
of inappropriate use.
As a result, water extracted from the environment is increasingly being priced at
a figure better reflecting its true value. This is resulting in major changes in the
use of water for agriculture, especially irrigation.
Irrigation
Consumption of water in Australia varies from year to year due to a variety of
factors, including the weather. In dry years more water is used.
10
The Australian Bureau of Statistics has collected and published detailed data on
an estimated 18 767 GL of water consumed in Australia in 2004-05:
• Agriculture accounted for 65 per cent
• Households eleven per cent
• Water supply eleven per cent
• Electricity and gas generation one per cent
• Manufacturing industry three per cent
• Mining industry two per cent
• Other industries six per cent
(a) Includes Services to agriculture; hunting and trapping.
(b) Includes Sewerage and drainage services.
(c) Includes water losses.
11
Mains water accounts for 36 per cent of total water use, and about 96 per cent of
Australian dwellings are connected to a mains water supply.
Reuse water made up 425 GL of water supplied or used by water providers in
2004–05, a 16% decrease from 2000–01 when it was 507 GL. In both reference
years, reuse water represented just under 4% of total water supplied by water
providers. This compares to 134 GL and 1% in 1996–97. Reuse water is defined
by the ABS as wastewater that may have been treated to some extent and was
then used again without discharge to the environment. Only reuse water
supplied to a customer by a water provider is included in this figure; water
reused on-site (for example water reused within a manufacturing plant) is not
included.
According to the ABS figures, most water is consumed in NSW (32 per cent)
and Victoria (27 per cent). Queensland’s water consumption rose 4 per cent
since 2000-01 to 23 per cent of the national total. The other states and territories
consume the remaining 18 per cent.
12
13
THE WATER CYCLE
When we turn on the tap, start the washing machine or take a shower, we don’t
necessarily think of the sun and the rain, but that is where the water comes from.
The process known as the water cycle begins with energy from the sun reaching
water in oceans, seas, rivers and lakes. Water evaporates and becomes water
vapour. As the water vapour rises, it cools and condenses into billions of
droplets to form clouds.
Vegetation is another source of water vapour. The roots of plants pump water
out of the ground and pass it into the atmosphere in a process known as
transpiration.
Clouds hold rainwater as long as they stay warm. If the air cools, the droplets
merge until they are so heavy that they fall back to Earth as rain, hail or snow.
The atmosphere is capable of holding about 10 days’ supply of rain – enough to
drop about 25 millimetres of freshwater over the entire surface of the planet.
14
Rain and snow falling within catchments can take several routes. Some
evaporates, some seeps into the ground to become groundwater and some stays
on or near the surface to form streams, and ultimately rivers.
The water cycle is also referred to as the hydrological cycle. Both terms
describe the solar-powered system that provides freshwater to the land-based
ecosystems upon which we depend.
15
URBAN WATER SYSTEMS
Introduction
When most Australians turn on the tap, they expect a continuous supply of safe
and pleasant drinking water. They expect it to flow at an acceptable pressure
and to be available even in the middle of a drought. They also expect their
wastewater will not create a nuisance or public health hazard. Furthermore, they
expect to be protected from localised or more substantial flooding.
During the 19th and particularly the 20th centuries, engineers have designed and
built urban water systems to meet these expectations.
Following is a brief overview of the main components of an urban water
system.
16
Collecting water
The entire area from which a stream or river receives its water is called a
catchment. A catchment is a natural drainage area, bounded by sloping ground,
hills or mountains, from which water flows to a low point.
Virtually everybody lives in a catchment, which may include hundreds of subcatchments. What happens in each of the smaller catchments will affect the
main catchment.
The water that comes out of a tap once flowed across a catchment – and that is
why catchments are a crucial part of urban water systems.
The quality of the catchment determines the quality of the water harvested from
it. Few communities have pristine water sources and the quality of water from
most sources is at risk from activities occurring in the catchment.
More About Catchments
Water resources can be classified as surface water or groundwater resources. In
both cases the quality of the catchment determines the quality of the water
harvested.
Groundwater is a significant source of supply in many parts of rural Australia. It
is also a significant ongoing source for several major urban centres.
Approximately 60 per cent of the water supplied to Perth, Western Australia
comes from groundwater sources, while Newcastle, New South Wales draws up
to 30 per cent of its supply from groundwater when surface water sources are
affected by drought. Also the regional water authority supplying Geelong,
Victoria and areas to its west has increased the utilisation of groundwater in
recent years as drought impacted on its surface water sources.
In parts of inland Australia, water from the Great Artesian Basin is used for
urban, agricultural and mining purposes. This water source is of vital
importance to outback regions of Queensland, New South Wales and South
Australia and is often the only available supply for towns and properties for
their domestic and stock-watering requirements.
For households not connected to mains water supply, and for some that are, a
private water supply can be an important resource. One example is stored
rainwater. The Public Health Division of the Victorian Department of Human
Services provides advice on the safe use of a private water supply. This advice
17
is available on the Internet:
http://www.health.vic.gov.au/environment/water/tanks.htm
A more detailed publication on rainwater tanks was produced by the National
Environmental Health Forum in 2004:
http://enhealth.nphp.gov.au/council/pubs/documents/rainwater_tanks.pdf
Storing water
In some urban water systems, the water supply is obtained directly from a river
or another body of freshwater. In others, rivers are dammed and the water
supply is distributed from artificial storages, such as reservoirs.
Dams are built across rivers and streams to create reservoirs to collect water
from catchments to ensure sufficient supply will be available when needed.
Dams also have been built for a range of purposes besides water supply, such as
agriculture and hydro-electricity generation.
Water may also be released from a reservoir as an “environmental flow” to
maintain the health of the ecosystem downstream of the reservoir.
It is estimated that the significant reservoirs built around the world store five
billion megalitres of water.
In Australia, more than 400 water storages are technically defined as “large
dams”. A large dam is defined by the Australian National Committee on Large
Dams (ANCOLD) as one that has an embankment more than five metres high.
There are also innumerable smaller water storages.
Australia’s largest reservoirs
Transporting water
Water is transported from catchments to communities by a variety of means
including pipelines, aqueducts, open channels or via natural waterways.
Treating water
Water that is to be used in an urban supply is treated to remove sediments and
contaminants and is also disinfected to kill potentially harmful microorganisms.
The treatment process may use conventional technologies or apply newer,
innovative approaches, to ensure the water is safe and pleasant to drink.
18
Supplying the distribution system
The water mains and pipes beneath the streets of a community are described as
the water supply distribution system or reticulation system. As part of this
system, strategically located service reservoirs store and supply enough water to
meet local peak demand at sufficient pressure. These service reservoirs are often
large covered tanks in an elevated position.
Pumps and valves also form an important part of the distribution system. The
end points of the system are the consumers’ taps.
Managing wastewater
Urban wastewater is known as sewage, and the pipes that transport sewage are
called the sewerage system.
No matter where you use water inside your home – the kitchen, bathroom,
laundry or toilet – it is discharged to the sewer. From there, your wastewater
begins a journey through a series of sewer pipes, pumps and mains to a sewage
treatment plant.
Wastewater from industry, schools, shops and other sources is also discharged
to the sewerage system.
At sewage treatment plants, wastewater is treated in a way that mimics natural
biodegradation processes. After intense treatment, the treated wastewater is
discharged back into the environment. Wastewater is treated to protect public
health and to minimize impacts on the ecosystems of receiving waters.
Treated wastewater is increasingly being recycled or reused in agriculture,
horticulture, golf courses and other businesses. A number of innovative housing
developments are using dual water supply systems where recycled wastewater is
supplied for some domestic purposes such as garden watering and toilet
flushing, while conventional drinking water is supplied for other household
uses.
Water recycling
Where homes and businesses are not connected to a sewage system, they will
usually have some form of on-site treatment of sewage. Such on-site treatment
needs to include provision for the safe discharge of the treated sewage into the
local environment to protect both public health and local ecosystems. The
septic tank is a common form of domestic on-site treatment.
19
Managing stormwater
Stormwater is the term used to describe the runoff from rain over an urban
catchment. In cities and towns, stormwater washes across roads and streets,
picking up oil, petrol, grease, sediment, industrial waste, leaf and other litter and
dog droppings on roads, streets and paths.
In rural areas, runoff may include agricultural and livestock waste, fertilisers
and pesticides.
Stormwater can also be contaminated by landfill leachate, septic tank effluent,
sewer spills and by illegal dumping. It is estimated that contaminated
stormwater causes up to half the pollution in surface and groundwater sources.
Most major urban centres now use separation systems, litter traps, grates,
retention basins or boom barriers to reduce the quantity of larger objects carried
in stormwater before it is discharged to the environment.
In recent years, water authorities have begun to explore the use of urban
wetlands to reduce the amount of sediments and soluble contaminants in urban
runoff. A leader in Australian research in this field was the Cooperative
Research Centre for Catchment Hydrology (http://www.catchment.crc.org.au/)
which has now become part of the eWater CRC:
(http://www.ewatercrc.com.au/).
20
WHAT IS DRINKING WATER?
A definition
A commonly used definition of drinking water is water that is intended for
human consumption and other domestic uses. It may be used directly from the
tap, or indirectly in beverages or foods prepared with water. Bathing and
showering may be among its other uses.
We expect drinking water to be safe to use and pleasant to drink. But what does
safe and pleasant mean? In Australia, the key reference material is a document
called Australian Drinking Water Guidelines. These guidelines state:
“drinking water should be safe to drink for people in most stages of normal life,
including children over six months of age and the very old. It should contain no
harmful concentrations of chemicals or pathogenic microorganisms, and ideally
it should be aesthetically pleasing in regard to appearance, taste and odour.”.
The guidelines also define drinking water as water “.. that, based on current
knowledge, is safe to drink over a lifetime; that is, it constitutes no significant
risk to health.”.
Water that meets all of the above criteria is also called potable water.
Internationally, the key reference to drinking water quality is the publication
from the World Health Organization (WHO) Guidelines for drinking-water
quality.
Since 1972, drinking water guidelines specifically developed for Australian
conditions have also been available. These Australian drinking water guidelines
have been based on the latest available version of the WHO guidelines but have
also been adapted to take into account a range of local circumstances.
Defining good quality drinking water
One difference between the WHO and Australian guidelines is that while the
WHO guidelines seek to define drinking water which, as well as being safe, is
aesthetically acceptable, the emphasis in the Australian guidelines is on defining
good quality drinking water.
More about the Australian Drinking Water Guidelines
21
WHAT ABOUT BOTTLED WATER?
Bottled water is sold all over the world. Many brands are sold as alternatives to
tap water. Other bottled waters with attractive packaging and promotion are sold
as soft drink and alcohol alternatives.
Bottled water is increasingly sold in plastic containers made from PET or
polycarbonate to meet market preference for this kind of packaging.
Within the bottled water market, there is a range of products. These include
mineral waters from natural springs and as well as waters harvested from other
more conventional sources. Some products are carbonated and others are “still”.
The Australian Drinking Water Guidelines do not address bottled water, or
other packaged water or ice. These products are regulated by Food Standards
Australia New Zealand under the Australia New Zealand Food Standard Code.
Standard 2.6.2: Non-alcoholic beverages and brewed soft drinks deals with
labelling and composition of packaged waters, mineral waters and water-based
beverages. The Code is available at Food Standards Australia New Zealand:
http://www.foodstandards.gov.au
A litre of bottled water purchased at a supermarket costs more than one dollar.
To fill a one litre bottle at the kitchen tap costs less than 0.1 cents. That is more
than a one thousand-fold difference in price.
The Australian Consumers’ Association magazine “Choice” published an article
in July 2005 comparing tap water and bottled water. They concluded that:
•
For most people, there’s no good reason to believe bottled water is any
healthier than tap water.
•
Bottled water doesn’t necessarily taste better than tap water.
•
Bottled water can be a handy alternative to soft drinks or juice when
you’re out and about, and it has no kilojoules.
The article can be found at www.choice.com.au (enter “bottled water” in the
‘Search’ field)
22
WHY TREAT WATER?
Drinking water is treated to protect public health by removing microorganisms
and natural or man-made chemicals that may cause illness in consumers. Water
treatment may also be used to improve the water’s colour, taste and odour as
required.
Protection of water sources from pollution by human or animal waste can
reduce the amount of microorganisms entering the water supply, but even water
from the most protected wilderness environment may sometimes contain
microorganisms capable of causing human disease. Illness can be easily and
rapidly transmitted to large numbers of people by contaminated water supplies,
therefore it is necessary to treat and/or disinfect water supplies to safeguard
against disease. This provides insurance or a barrier against actual or potential
contamination.
While some earlier civilisations apparently appreciated the importance of a
clean and reliable water supply, the development of scientific understanding of
why this was important did not occur until the second half of the 19th century.
This was when the nature of infectious disease was first understood and the
ability of water supplies to transmit diseases such as cholera and typhoid was
first demonstrated.
The observations of Dr John Snow (1813–1858) were important in showing this
link between water supply and disease. He began his work during a major
cholera outbreak in Britain in 1848–49 in which at least 53,000 people died. His
systematic investigation of the 1854 outbreak in London showed that cholera
death rates were much higher in people consuming water from sewage-polluted
regions of the Thames River than in people drinking water from a cleaner part
of the river.
At that time the germ theory of infectious disease was unknown, and cholera
was thought to result from "bad air" or "filthy conditions". John Snow proposed
that cholera was transmitted by a "specific poison" (now known to be the
bacterium Vibrio cholerae) that could be transmitted from person-to-person or
indirectly through contaminated water, food or objects.
Dr Snow is best remembered for an incident related to a cholera outbreak in the
Golden Square section of London where more than 500 people died within 10
days. He determined that most of the sick people drank water from the Broad
Street pump, while residents with a different water supply were not affected.
After his findings were reported to the Board of Guardians of the parish, the
23
handle of the pump was removed as a public health measure to prevent people
using the water. A memorial to Dr Snow now marks the place where the pump
once stood.
Dr Snow's findings were published in 1855 in the classic work On the Mode of
Communication of Cholera, however it was another 30 years before the germ
theory of infectious disease was fully accepted.
Link to UCLA site on Dr John Snow:
http://www.ph.ucla.edu/epi/snow.html
The approach to the provision of water services that emerged from this 19th
century experience was to separate as much as possible the sources of water
supply from human habitation and waste disposal. Since complete protection of
water sources was often not possible, methods of treating water to kill or
remove microorganisms were also developed.
The technologies used to treat water are similar worldwide. There have been a
great variety of treatment processes developed and the more important of these
are discussed elsewhere in this Guide. The choice of treatment technology
depends on the characteristics of the source water, the types of water quality
problems likely to be present, and the costs of different treatment systems.
Innovative water treatment technologies are being developed in Australia and
overseas with the aim of improving water quality further and reducing the cost
of doing so. Much of this Australian research is conducted within the
Cooperative Research Centre for Water Quality and Treatment.
Water treatment, together with improved sanitation, has produced great benefits
to public health in developed countries by reducing the incidence of many
diseases. However, in the developing world, waterborne diseases are still a
major cause of illness and death, especially in children. In 2002 the World
Health Organisation estimated that over 1.1 billion people (17% of the world’s
population) lacked access to improved water supplies, and 2.6 billion (42%)
lacked basic sanitation facilities. The United Nations General Assembly has
proclaimed 2005-2015 as the Water for Life decade, with increased focus on
achieving the twin goals of providing safe water and basic sanitation to people
in developing countries.
More information can be found on the Water, Sanitation and Health
(http:/www.who.int/water_sanitation_health/en/) page of the World Health
Organisation website.
24
Treatment aims to ensure that water is:
• Safe for human consumption.
• Pleasant to consumers.
• Provided at a reasonable cost.
25
HOW IS WATER TREATED?
Introduction
The water treatment processes developed in the 19th century and refined during
the 20th century are simple in nature. However, engineers have since developed
ways of making these processes happen faster, in a smaller area and in a more
controlled way at lower cost.
These earlier technologies are referred to as traditional or conventional
technologies to distinguish them from technologies developed more recently.
There are a great variety of water treatment processes, although only a few are
applied in most situations. A summary of each of the main treatment processes
is given below.
Coagulation, flocculation and sedimentation
In traditional water treatment, certain chemicals are added to raw water to
remove impurities. While some particles will spontaneously settle out from
water on standing (a process called sedimentation), others will not. To cause
particles that are slow to settle or are non-settling to settle out more readily, a
soluble chemical or mixture of chemicals is added to the water. Such a chemical
is called a coagulant and the process is called coagulation.
The coagulant reacts with the particles in the water, forming larger particles
called flocs, which settle rapidly.
Flocs can also be effectively removed by passing the water through a filter. The
process is controlled so that the coagulant chemicals are removed along with the
contaminants.
Coagulation/flocculation processes generally use aluminium sulphate (alum) or
ferric chloride as the coagulant.
A combination of coagulation/flocculation/sedimentation and filtration is the
most widely applied water treatment technology around the world, used
routinely for water treatment since the early part of the 20th century.
Coagulation/flocculation processes are very effective at removing fine
suspended particles that attract and hold bacteria and viruses to their surface.
26
Research has shown that these processes alone are capable of removing up to
99.9 per cent of the bacteria and 99 per cent of the viruses from water supplies.
These processes also remove some of the organic matter washed from soil and
vegetation as water travels across the landscape, from raindrop to river. It is
usually this natural organic matter that is responsible for any brown
discolouration in water. However, not all of this natural organic matter (what
water scientists call NOM) is removed by coagulation: certain taste and odour
problems may remain.
Filtration
One of the oldest and simplest processes used to treat water is to pass it through
a bed of fine particles, usually sand. This process is called sand filtration. In its
simplest form, the water is simply passed through the filter with no other pretreatment, such as the addition of a coagulant. Usually this type of filter will
remove fine suspended solids and also some other particles such as larger
microorganisms.
Sand filtration is even more efficient when the water being treated passes
through the sand filter very slowly. Over time the sand particles become
covered with a thin surface layer of microorganisms. Some might refer to this
layer as a slime but water scientists call it a biofilm. Even very small particles
stick to this biofilm and are held, while water of greatly improved quality passes
out through the filter.
First operating in London in the 19th century, slow sand filters are still widely
used throughout the world today. Although very effective, they require a large
area of land to achieve the sort of flows required by a large modern city.
Additional processes may also be needed to achieve adequate water quality.
In the early 20th century, engineers developed rapid sand filters, which use high
rates of water flow and sophisticated backwashing of the filter bed to remove
trapped contaminants.
Because the sand filtration processes become less effective at removing fine
suspended particles at higher water flow rates, the water must be pretreated –
coagulated and flocculated – before passing through the filter bed. Such high
rate direct filtration processes are widely applied to raw water with low levels of
suspended matter. A good example is the water treatment plant at Prospect in
Sydney.
The water treatment plant at Prospect in Sydney is one of the largest direct
filtration plants of its type in the world. The plant produces more than 2000
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megalitres a day of treated water. It is operated by Australian Water Services on
behalf of Sydney Water Corporation. The raw water being treated at Prospect
comes from Warragamba Dam, operated by Sydney Catchment Authority.
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Membrane filtration
29
The development of plastics has led to a new range of filter materials and
methods. Processes based on these new filter materials are now increasingly
used to treat water for urban and industrial purposes.
In membrane filtration, water is filtered through tiny holes (usually referred to
as pores) in a membrane wall rather than a bed of sand. The smaller the pore
size, the greater the proportion of material the membrane retains as the water
passes through.
Processes of membrane filtration are categorised by the pore size in the
membrane. Pore size can vary from 0.1 microns (1000 microns is equivalent to
1 millimetre) for microfiltration down to 0.001 microns for nanofiltration.
The most common form of microfiltration membrane is a one-metre long
bundle of thin, thread-like hollow fibres. A microfiltration water treatment plant
would contain many such bundles.
A cross-section of a single hollow fibre is shown below (in yellow). Particles (in
brown) are retained on the outer surface of the membrane while the purified
water (in blue) passes into the central channel from where it flows lengthwise
along the hollow fibre.
Previously too expensive to use in many circumstances, recent advances have
reduced the cost of membrane filtration to a level approaching that of
conventional water treatment processes.
While membrane water treatment plants are simple and reliable in operation,
especially in small to medium-sized applications, there are some disadvantages.
High energy costs are involved in pumping the water through the membrane. If
a lot of natural organic matter is in the water, the membrane tends to block
easily. This is referred to as membrane fouling. If cleaning cannot reverse the
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membrane fouling, the life of the membrane will be significantly shortened.
This increases the cost of water treatment, since replacing membranes regularly
is expensive.
Microfiltration
Microfiltration will remove most of the fine suspended solids in the water and
almost all protozoa and bacteria but is not able to remove the dissolved part of
the natural organic matter in the water. It is this dissolved part of the natural
organic matter that is frequently the cause of colour, taste and odour problems.
The microfiltration process is becoming increasingly popular for small-scale
water treatment plants supplying smaller communities in rural and regional
Australia. It has become the most widely used membrane water treatment
process in Australia.
Microfiltration plants installed by water authorities in recent years include:
Batlow (Tumut Shire Council, NSW)
Babinda, Bramston Beach and Mirriwinni (Cairns City Council, Queensland),
Crystal Creek (Townsville Thuringowa Water Supply Board, Queensland),
Coen (Cook Shire Council, Queensland)
Birregura and Meredith (Barwon Water, Victoria)
Creswell, Frogley and Yarra Glen (Melbourne Water, Victoria)
Gunbower, Tooborac and Trentham (Coliban Water, Victoria).
Ultrafiltration
Ultrafiltration membranes have smaller pores than those used in microfiltration
and can therefore remove finer particles from the water. This process is capable
of removing almost all the viruses (the microorganisms most difficult to
remove) and improving colour.
Because of the relatively high levels of natural organic matter found in raw
waters in Australia, ultrafiltration technology has not found wide application
here at this stage of its development.
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Nanofiltration
Nanofiltration uses membranes with even smaller holes than for ultrafiltration,
so requires a high operating pressure to force the water through the membrane.
This results in high energy and operating costs.
However, nanofiltration is more effective than other filtration methods at
improving water quality. For example, it is capable of removing all virus
particles and most of the NOM. However, it also removes some natural minerals
from the water, which can cause pipes to corrode. To reduce corrosion in these
circumstances, stabilising chemicals, such as lime, must be added to the treated
water.
The cost involved in using this technology, and the fact that backwashing of the
membrane can consume a significant proportion of the water produced, limits
its use to specific circumstances.
There are no working examples of a nanofiltration plant in Australia at present,
but the process is in operation elsewhere, including Europe, where it is used to
treat surface waters contaminated by herbicides and insecticides.
Additional Treatments for Unusual Circumstances
While coagulation processes and/or filtration remove most of the troublesome
contaminants from water, they usually do not remove all of the dissolved (or
soluble) material. This includes low concentrations of dissolved organic matter
that microorganisms in the water can use as a food supply and perhaps algal
toxins and associated taste and odour compounds.
If water contains undesirable contaminants, additional treatment processes are
required, like adsorption and oxidation.
Adsorption refers to the process by which chemicals are attracted to and held by
a solid surface and is quite different from the similarly sounding process of
absorption.
In water treatment, specialised adsorbent materials are used. Examples are
activated carbon and ion exchange resins. These adsorbants can be used to
remove purely soluble contaminants from water.
Activated carbon is the most widely used adsorbent material in water treatment,
because it is highly effective in removing taste and odour compounds and algal
toxins. It can be used as a powder or in granular form.
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In Australia, there has only been limited use of granulated activated carbon. In
this treatment process, the activated carbon is usually placed in a column or
filter and the water percolated through the bed of carbon granules. After some
time the activated carbon will become saturated with the adsorbing material and
will need to be replaced or regenerated. Current technology to regenerate the
carbon granules involves heating in a high temperature furnace. Because of the
cost of this regeneration process, it has not been used in Australia.
If water contamination occurs only occasionally, a better approach is to add
powdered activated carbon to a conventional coagulation/flocculation process
when the problem arises. The carbon is collected in the filters and then
discarded with the normal water treatment plant sludge. Such intermittent
dosing of activated carbon powder is used in Australia at numerous locations
that have problems with blue-green algal blooms.
The use of activated carbon is a very costly and can be justified only when there
are particular problems with toxins or taste and odour compounds.
Ion exchange resins can also remove soluble materials from water by
exchanging ions (charged atoms or molecules) in the water and on the resin.
This form of treatment is more often used for industrial purposes in industries
that require very pure water for specialised processing, for example in computer
chip manufacture. It has also found general application in the treatment of boiler
feed water to reduce the problem of scaling.
With new developments in the technology, ion exchange resins are also being
used to treat urban water supplies. For instance, the Water Corporation of
Western Australia has established the biggest ion exchange water treatment
system of its type in the world at the Wanneroo Groundwater Treatment Plant to
remove intermittent odour problems occasionally experienced in some of
Perth’s groundwater supply schemes. This plant uses an Australian invention,
MIEX (magnetic ion exchange) resin manufactured by Orica Watercare.
Another treatment technology commonly used in Europe but only now
appearing in Australia is oxidation with chemicals such as ozone or chlorine
dioxide. These are strongly reactive chemicals able to oxidize a range of
substances in water.
Ozone in particular is a strong oxidizing agent and is used as a disinfection
agent (see below) and as a means of destroying soluble contaminants such as
algal toxins, taste and odour compounds and (particularly in Europe) trace
levels of insecticides. It is quite often used in combination with a column of
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granular activated carbon, as any soluble organics remaining after the chemical
oxidation stage are biologically degraded by the film of microorganisms that
develops in the activated carbon bed.
Experience with the process in Europe has been very good, with consumers
reacting positively to the improved taste of the water produced. However, the
technology is more expensive than standard coagulation and is suited to
applications only where taste and odour problems are becoming severe. For
example, Grampians Water, supplying water services in the Wimmera region of
Victoria, has installed such a plant at Edenhope to overcome problems caused
by algal contamination of the local water source.
Water Stabilisation
Some raw water supplies are not stable, becoming acidic or alkaline depending
on which material they are in contact with. This condition often leads to
corrosion in piping systems and hot water services and can result in dissolved
metals appearing in the water. For example, where copper corrosion occurs, a
telltale bluish stain can appear where a tap drips on to a surface.
To prevent such corrosion problems, many waters are chemically stabilised
before distribution by the addition of lime and sometimes carbon dioxide. The
addition of lime (calcium carbonate) will make the water slightly harder by
increasing the level of calcium in the water. Here, hardness refers to the
characteristic of the water that prevents soap from lathering. In contrast, soft
water will allow soap to form a lather easily.
Disinfection
Disinfection is carried out to kill harmful microorganisms that may be present in
the water supply and to prevent microorganisms regrowing in the distribution
systems.
Good public health owes a lot to the disinfection of water supplies. Without
disinfection, waterborne disease becomes a problem, causing high infant
mortality rates and low life expectancy. This remains the situation in some parts
of the world.
There can be no higher priority in any water supply system than effective and
safe disinfection of the water. The only possible exception to this rule occurs
with secure groundwater supplies, where harmful microorganisms are prevented
from entering the underground water source or contaminating the water when it
34
is brought to the surface. Such water supplies need to be inspected and tested
regularly to make sure that they remain safe.
The two most common methods to kill the microorganisms found in the water
supply are oxidation with oxidising chemicals or irradiation with ultra-violet
(UV) radiation.
The most widely used chemical disinfection systems are chlorination,
chloramination, chlorine dioxide treatment and ozonation.
Key factors considered by a water authority in selecting a disinfection system
are:
• Effectiveness in killing a range of microorganisms.
• Potential to form possibly harmful disinfection byproducts.
• Ability of the disinfecting agent to remain effective in the water throughout
the distribution system.
• Safety and ease of handling chemicals and equipment.
• Cost effectiveness.
A summary of each of the main disinfection processes is given below.
CHLORINATION
Chlorination is the most widely used disinfectant for drinking water in
Australia. Its introduction a century ago removed the threat of cholera and
typhoid from Australian cities.
It is cheap, easy to use, effective at low dose levels against a wide range of
infectious microorganisms, and has a long history of safe use around the world.
Chlorine is a strongly oxidising chemical and may be added to water as chlorine
gas or as a hypochlorite solution.
Chlorine’s main disadvantage is a tendency to react with naturally occurring
dissolved organic matter to form chlorinated organic compounds.
The substances formed by the disinfectant reacting with the natural organic
matter in the water are referred to as disinfection byproducts.
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In the 1970s, as scientific instruments capable of measuring lower and lower
concentrations of substances were developed, trace quantities of chloroform and
other similar chemicals were identified as disinfection byproducts in chlorinated
water supplies.
While the concentration of these disinfection byproducts is usually very low (a
typical figure might be 0.1 part per million), some have been identified as
potential carcinogens. As a precaution, many countries limit the allowable level
of chlorinated disinfection byproducts in the water. The Australian Drinking
Water Guidelines also suggest maximum values for a range of byproducts (for
example, 0.25 part per million for chloroform-type compounds).
Studies have compared the health risk from microbiological contamination of
drinking water with the potential chemical risk from chlorination byproducts.
The conclusions so far are:
• The risk of death from pathogens is at least 100 to 1000 times greater
than the risk of cancer from disinfection byproducts.
• The risk of illness from pathogens is at least 10,000 to one million times
greater than the risk of cancer from disinfection byproducts.
The Australian Drinking Water Guidelines encourage action by water
authorities to reduce organic disinfection byproducts in water supplies but not in
a way that would compromise the proper disinfection of the water.
The likelihood of such byproducts forming can be greatly reduced by treating
the water to lower levels of dissolved organic matter before chlorine is added
for disinfection purposes.
Some Australian examples of chlorinated water supplies are those of
Melbourne, Adelaide, Perth, Canberra, Hobart and Townsville.
CHLORAMINATION
Chloramines are produced when ammonia and chlorine are added to water
together. They are less effective than chlorine in killing microorganisms
because they are not as chemically active. However, chloramines maintain their
disinfecting capability longer than chlorine and are ideal for very long
distribution systems or for water supplies with long holding times in service
reservoirs. For example, the disinfected water supplied to some Australian
communities may travel through the distribution system for more than a week
before use as drinking water from someone’s tap.
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Chloramines also react less with dissolved organic matter in the water and so
produce fewer disinfection byproducts.
Chloramination is a common disinfection system in Australia and many
examples of its use can be found in regional Australia.
CHLORINE DIOXIDE
Chlorine dioxide is about 10 times more expensive than chlorine and its use in
Australia is very limited. Its most significant use is by the Gold Coast City
Council in Queensland.
The choice of chlorine dioxide in this application was primarily to prevent an
aesthetic water quality problem caused by naturally occurring manganese
compounds in the raw water. The problem is sometimes described as “black
water” and can result in black stains on customers’ washing. When “black
water” occurs, the material being washed effectively acts as a filter for the tiny
black particles during the rinse cycle of the washing machine.
Chlorine dioxide is a strong oxidant that can be used in low doses. It is a highly
reactive, unstable gas that must be generated at the water treatment plant from
sodium chlorite. Its use does not lead to the formation of chlorinated
disinfection byproducts, but other possible byproducts of oxidation, such as
chlorate and chlorite ions, can be a public health concern.
OZONE
Ozone (O3) is the most powerful disinfectant used in water treatment. It is even
effective against the difficult to treat protozoan parasites, Cryptosporidium and
Giardia.
Ozone, which only recently began to be used in Australia, destroys soluble
contaminants such as algal toxins, taste and odour compounds and trace levels
of insecticides.
Ozone is an unstable gas that must be generated at the water treatment plant.
This is done by passing an electric discharge through clean, dry air or oxygen.
Because it is so reactive, ozone decays quickly in water. For this reason, it is
usually used together with a small dose of chlorine or chloramine to ensure that
some residual disinfection capacity is maintained in the water supply
distribution system to prevent regrowth of microorganisms.
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The use of ozone does not lead to chlorinated disinfection byproducts. However
other possible oxidation products, such as bromate formed from the naturally
occurring bromide found in some water sources, are a potential health concern.
ULTRAVIOLET IRRADIATION
Ultraviolet radiation (UV) is a component of sunlight. Sunlight achieves
disinfection by ultraviolet irradiation naturally. In water treatment, an
appropriate level of UV irradiation, produced by mercury lamps, can kill
bacteria and viruses. However, there is some uncertainty surrounding the
effectiveness of UV irradiation against Cryptosporidium and Giardia.
UV irradiation adds no chemicals to water and uses equipment that is relatively
simple to operate and maintain. However, impurities in the water that cause
colour and turbidity can severely reduce the effectiveness of the process because
UV radiation cannot penetrate the water effectively.
UV irradiation has no lasting effect and a further disinfectant such as chlorine or
chloramine is usually added to ensure that some residual disinfection capacity is
maintained in the water supply distribution system to prevent regrowth of
microorganisms.
The cost of UV treatment of water supplies is becoming increasingly affordable,
especially for small water supply systems where the raw water is clean and cold.
UV irradiation may also be chosen where the water source is close to the
customers, allowing only a short time between when the water is disinfected
and when it is consumed.
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IS A WATER FILTER NECESSARY?
Generally, people living in major Australian cities and also in many parts of
regional Australia, do not require a filter to meet health requirements because of
the quality of water supplied.
Filters can change the aesthetic quality and taste of drinking water. Installing a
filter for these reasons is a matter of choice.
Those people who choose to install a filter should make sure that it meets their
specific needs and is properly maintained.
Maintenance of a water filter is very important from a health perspective. If the
filter is not changed frequently, a build up of microorganisms or chemicals may
be released back into the water resulting in worse, not better quality, water.
The Australian Consumers’ Association magazine “Choice” published an article
on water filters in February 2003. According to the “Choice” article most
Australians usually do not have to worry about the quality of their drinking
water. The article can be viewed at www.choice.com.au (enter “water filters” in
the ‘Search’ field)
Where there is a concern about any aspect of the quality of the local water
supply, it is advisable to contact the water supplier in the first instance.
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DELIVERING WATER TO THE COMMUNITY
The distribution system
After water has been treated to protect public health and improve its’ aesthetic
properties by removing colour and taste and odour as required, it is ready to be
delivered to consumers. The system of mains and pipes used to deliver the water
is known as the distribution, or reticulation, system.
Treated water may be held at a treatment plant or immediately discharged into
the system of mains and pipes that will transport it to consumers’ taps. On the
way it may be held in short-term storages, usually known as service reservoirs,
which are located as close as possible to where the water will be used.
Sufficient water is required in a local area to supply periods of high demand, as
on a hot summer day. From a design perspective, the needs of fire services
usually determines the capacity of the system.
An important characteristic of a drinking water distribution system is that it is
closed, to prevent contamination by birds, animals or people. In contrast,
irrigation water is usually delivered in open channels or aqueducts.
A significant part of the water supply system lies buried underground. Out of
the public eye, such infrastructure can be overlooked. It is easy to forget how
valuable and essential water distribution systems are to the community. In terms
of money spent on supplying water in Australia, most of it has been invested in
the mains and pipes buried under the streets of towns and suburbs across the
country.
Most distribution systems have developed and expanded as urban areas have
grown. A map of a water distribution system would show a complex mixture of
tree-like and looped pipe networks, together with valves and pumps.
Distribution systems require regular cleaning (flushing and scouring),
maintenance and a program to replace pipes and other equipment as they near
the end of their useful lives. Water mains can be expected to have a useful life
of 40 to 100 years. Many of the pipes under the older parts of our cities may be
towards the upper end of this range.
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Dual pipe systems
In future, it is possible that many Australian communities will be supplied with
water of two qualities: one of drinking water quality and the other of a quality
that is not safe for drinking but which is suitable for other purposes such as
toilet flushing and outdoor use.
Such dual systems have been used in other parts of the world and in recent years
have been trialed in Australia. For example, in Sydney, New South Wales, a
new housing development at Rouse Hill has been built with a dual pipe system.
More recently, housing developments at Newhaven and Mawson Lakes in
Adelaide, South Australia have also featured dual pipe systems.
This system has the advantage of using less high quality water where lower
quality water will do, but it is difficult and expensive to dig up existing suburbs
and install dual pipe systems. In addition, there are public health risks if crossconnections occur between the two systems.
Cross-connections
If a connection is accidentally made between a pipe carrying high quality
drinking water and water of low quality, the drinking water can be
contaminated.
Most cross-connections occur when a backflow of contaminated water mixes
with the water in a supply pipe. This usually happens when the drinking water
supply is at a lower pressure than the contaminated source. A range of devices
has been developed to limit the potential for backflow and cross-connections.
Standards Australia has several Australian/NZ standards to manage
backflow/cross-connections.
Another possible source of contamination is a fall in distribution system
pressure, which allows contaminated groundwater to enter the system through
the gap in a joint or other similar route.
What about rural and remote communities?
Most Australians live in cities where large investments have been made to
ensure an adequate supply of water, even in times of drought. Approximately
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seventy per cent of Australians live in cities containing more than 100,000
people. These cities represent less than one per cent of the area of Australia. The
other ninety-nine per cent of this large land contains the other thirty per cent of
Australians. Many of those people live in smaller cities and towns and also have
an adequate mains water supply. However, some do not.
For communities not connected to mains water supply, some provision for the
supply of water is essential. This could be, for example, groundwater, stored
rainwater or a combination of both.
The safe use of a private water supply is discussed under Urban Water Systems.
However for many small communities in remote parts of Australia, the
provision of an adequate supply of water is a major challenge. Many of these
communities are Aboriginal and Torres Strait Islander communities.
ABORIGINAL AND TORRES STRAIT ISLANDER COMMUNITY WATER SUPPLIES
A significant proportion of the small settlements in Australia with less than a
thousand inhabitants are Aboriginal and Torres Strait Islander communities.
Some understanding of the needs of these communities can be obtained from an
Australian Bureau of Statistics survey published in 2001 which details
community housing and infrastructure needs (CHINS 2001). At the time of the
survey:
• There were a total of 1216 discrete Indigenous communities throughout
Australia.
• Ninety per cent of Indigenous communities were considered very remote
in terms of accessibility and distance from a main centre.
• Seventy-three per cent of the discrete Indigenous communities had a
usual population of less than 50.
Many of these communities still have inadequate water supplies and some do
not have a reticulated water supply at all. The provision of water services to
small remote communities is particularly difficult. The remoteness makes it
slow and expensive to get materials delivered. It also makes it difficult to get
maintenance teams and support services on site.
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For the communities themselves, on-going maintenance and repairs to water
supply systems is difficult because community members generally lack access
to the required technical training and to the specialised services that might be
needed.
Water provision in Aboriginal and Torres Strait Islander communities was the
subject of a Human Rights and Equal Opportunity Commission Report in 1994.
The Report recognised the practical difficulties associated with the provision of
adequate water services to remote communities and acknowledged that
government departments and agencies had made efforts to improve water
supplies in remote Indigenous communities. However, it concluded that no
significant improvement in Aboriginal living conditions would occur without a
number of other developments. These included:
• recognition of the need for community control in decision-making
• recognition of difference between cultures
• development of the means for communities to receive and respond to
independent scientific and technical advice
• consideration of how to achieve sustainable development solutions
• identification and implementation of the necessary changes in
Government policies and programs
In the Report, the Federal Race Discrimination Commissioner stated:
“If equality is assessed on outcomes (not inputs or the stages leading to the
outcome), useful options are created for the consideration of the water supply.
It is now possible to ask whether the desirable outcome is going to be a
reticulated water supply which delivers water that meets NHMRC Guidelines or
whether it is that people have free and unimpeded access to water supply which
they can afford and over which they can exercise control to the extent of
adjusting the system to suit their changing circumstances”
The Report argued that it was important to ensure that water was safe to drink
but that it was also important that Aboriginal and Torres Strait Islander people
were able to make their own decisions about how it was provided and
maintained.
Progress made in the light of the recommendations contained in the
Commission’s 1994 report was reviewed on behalf of the Federal Government
in 2001. That review is available at
www.hreoc.gov.au/racial_discrimination/water_report/index.html
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The CRC for Water Quality and Treatment has an active involvement with a
number of remote Indigenous communities, providing scientific and technical
advice in support of their efforts to achieve improvements with their water
supply. In these activities the CRC works closely with many other organisations
and in particular with the Centre for Appropriate Technology in Alice Springs
Further information on the Centre for Appropriate Technology is available at:
www.icat.org.au
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WATER AND HUMAN HEALTH
Introduction
The importance of good drinking water in maintaining human health was
recognised early in human history, with water storage and treatment mentioned
in historical records dating back to at least several hundred years BC.
In more recent times, the studies of Dr John Snow on the transmission of
cholera by London's drinking water in the mid-1800s contributed to the
recognition that specific microorganisms cause specific human diseases.
By the early 1900s, better protection of water supplies from sewage pollution
and simple but effective methods of water treatment (chlorination, sand
filtration) greatly reduced rates of waterborne disease in developed nations.
However, waterborne diseases continue to be a major cause of illness and death
in the developing world, especially in children.
Since most people drink water every day, contamination of a public drinking
water supply has the potential to expose nearly all members of a community to
harmful chemicals or microorganisms in a very short period of time. For this
reason, it is important that the protection of public health is the first
consideration in managing any water supply.
Waterborne diseases
Microorganisms that are capable of causing disease are called pathogens. The
pathogens of concern in water supplies are mainly those that are found in the
excrement (faeces) of humans or animals. If these microorganisms are present
in water, and are not removed by water treatment or disinfection, then
consumers may suffer infections.
Many types of pathogenic bacteria, viruses, protozoa and helminths may be
transmitted by contaminated water supplies. These pathogens can also be
transmitted directly from human to human, from animal to human, from
swimming in contaminated water, by contaminated food, or indirectly through
contact with contaminated objects. The fact that contaminated water causes an
outbreak of a particular disease does not mean that the disease is only or mainly
transmitted by water under normal circumstances.
Generally, faecal contamination from human sources is regarded as the greatest
risk to water supplies, as some diseases such as cholera, typhoid, and
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gastroenteritis viruses are found only in humans. However, some pathogens
from animals including mammals and birds can also cause illness in humans.
More on pathogens
Zoonotic diseases
Zoonotic diseases or zoonoses are those diseases that are naturally transmitted
between vertebrate animals and humans. Mammals in catchments and birds in
service reservoirs are the most common cause of waterborne zoonotic disease.
For example, Salmonella bacteria entering the water supply from such sources
can result in waterborne zoonotic disease.
Zoonoses can be spread from pets, such as dogs and cats, and agricultural
animals (cattle, sheep and pigs), or from native or feral animals.
The lack of a safe water supply and waste disposal system causes waterborne
disease to spread easily in poorer countries. For example, several serious
diseases are spread by freshwater snails associated with irrigation canals in
certain areas, as well as by bathing, swimming, wading and washing clothes in
such waters.
Water also plays a role in the transmission of other types of diseases. For
instance, insects that breed in water, such as mosquitoes, may also spread
disease to humans by sucking blood. Such diseases include typhus, dengue
fever, malaria and yellow fever.
The amount of illness in a community is affected by the quantity of water that is
available, as well as its microbiological quality. If there is not enough water for
people to bathe themselves, or to wash cooking utensils or clothing, high rates
of gastroenteritis are common. In this situation, increasing the amount of water
for people to use will generally produce a health benefit even if the quality of
the water is not changed.
More on water-related diseases
What do the Guidelines say?
The 2004 edition of the Australian Drinking Water Guidelines incorporates a
Framework for Management of Drinking Water Quality that provides guidance
on assessing and managing risks to drinking water supplies throughout the
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water supply system. This Framework emphasises a preventive approach so that
potential problems can be identified and managed to avoid impacts on the
quality of water supplied to consumers. Ensuring the microbiological safety of a
water supply entails a wide-ranging program of protection, treatment and
monitoring, with barriers to the entry and transmission of pathogens throughout
the system.
The barriers should include most of the following:
• The water sources selected should be protected from contamination by
human or animal faeces and an active catchment management program
maintained.
• Water should be pre-treated, for example by detention and settling in
reservoirs for long enough to allow bacteria to die off (at least several
weeks but preferably longer).
• Water storages should be protected from public access, malicious or
accidental contamination and vandalism.
• Some form of treatment (such as coagulation, settling and filtration)
should be carried out.
• The water should be disinfected before it enters the distribution system.
• An adequate concentration of disinfectant should be maintained
throughout the distribution system. This is referred to as the disinfectant
residual.
• The distribution system should be secure against possible recontamination.
In addition, the Guidelines discuss monitoring of water quality and water
treatment processes as a check that the barriers to contamination are working.
In summary, the Australian Drinking Water Guidelines highlight the concept
of a preventive risk management approach incorporating multiple barriers to
prevent pathogens or other contaminants reaching consumers. Such barriers
may include:
• Protected catchments
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•
•
•
•
Storage reservoirs
Treatment plants
Disinfection systems
Closed distribution systems
How do you know if there are bugs in the water?
Protection of public health depends on having multiple barriers in place to keep
bugs (pathogenic organisms) out of the water supply. This includes trying to
keep them out of the catchment or water source in the first place. Other barriers
to these organisms are water treatment technologies, disinfection and a closed
distribution system.
Measurement of pathogens in the water may appear to be the best method to
determine whether the water supply is safe. However, this is an immensely
difficult task, requiring expensive and sophisticated technology and taking
considerable time.
It is also a very complex task due to the diversity of pathogens that exist and the
different test methods required. A further problem is the inability of existing
technology to continually monitor for pathogens. Because of these factors,
indirect methods are used to measure microbiological water quality.
One such method is to measure the concentration of disinfectant at various
points throughout the distribution system. If chlorine is used as the disinfectant,
what is referred to as the chlorine residual is measured. According to the
Australian Drinking Water Guidelines, a chlorine residual of 0.2 milligrams
per litre (mg/L) to 0.5mg/L is generally adequate. Chlorine at this level kills the
target organisms.
The second method of measuring microbiological water quality is to monitor for
organisms that might indicate that the water is contaminated with faecal
material or that disinfection is inadequate. These organisms are referred to as
indicator organisms. They are not harmful to health but their presence indicates
that other faecal organisms (including harmful pathogens) may also be present
in water.
Members of the coliform group of bacteria are used as indicators of water
quality. This group contains many species of bacteria that grow in the
environment, but a sub-group of coliform bacteria, called thermotolerant
coliforms (coliforms preferring warmer temperatures), are found predominantly
in the intestine and faeces of humans and other warm-blooded animals.
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One member of the thermotolerant coliform group, Escherichia coli (often
referred to as E. coli) is recognised as the most specific indicator of recent
faecal contamination in water supplies. This organism is now the preferred
indicator for assessing the microbiological quality and safety of drinking water.
In some instances, a more general test for thermotolerant coliforms may be used
instead of a specific test for E. coli, however thermotolerant coliforms are a less
specific indicator of faecal contamination. Some non-faecal environmental
coliform bacteria (Klebsiella, Citrobacter and Enterobacter) are also
thermotolerant, and in certain circumstances these may produce a positive result
on the test even if faecal contamination is absent.
Other groups of bacteria may be used by water suppliers as operational
indicators to assess whether water supply systems are operating normally as
expected. These organisms (total coliforms and heterotrophic plate count
bacteria) have no significance for assessing health risks but unusual variations
in their numbers may signal a change from normal operating conditions that
requires investigation.
Indicator organisms can be used to:
• Measure the effectiveness of treatment processes including disinfection.
• Indicate the risk of faecal pathogenic organisms being present in the water
supply.
• Provide evidence of recent faecal contamination from warm-blooded
animals.
The indicators most commonly used to measure the microbiological quality of
water are E. coli, and thermotolerant (or faecal) coliforms.
More on indicator organisms
Do chemicals in water affect human health?
A wide variety of chemicals may enter a body of water used for water supply
purposes via stormwater runoff. Such chemicals can be natural or manufactured
substances.
49
Inorganic chemicals, such as mineral salts, can be leached from the natural
environment. Manufactured chemicals such as pesticides, herbicides,
insecticides, pharmaceuticals and industrial waste products can also be picked
up from the land in the catchment or discharged into a waterway from a specific
source.
Every chemical has an effect on living organisms exposed to it. The study of the
negative or harmful effects of chemicals on living organisms is known as
toxicology.
Living organisms respond in different ways when exposed to chemicals. Some
effects in organisms are immediate; that is, they show up within 24 to 48 hours.
Other effects may be delayed and not show up for 10 or 20 years or more; for
example, cancer in humans.
The response of a living organism exposed to a chemical depends upon the
chemical dose or the exposure level. Generally, the higher the dose the more
significant the effect. Simply knowing that the compound is carcinogenic is not
sufficient to assess the risk to human health – it is necessary to know the
harmful dose as well.
Ingestion of low levels of some chemical contaminants in drinking water over
long periods of time has been associated with negative health effects, but these
associations are not fully understood.
The Australian Drinking Water Guidelines provide guidance to water
authorities on safe levels of chemicals in drinking water based on the best
scientific information available.
Inorganic chemicals in water
Inorganic chemicals may be present naturally in raw water, be derived from
contamination of source water or obtained from contact with piping and
plumbing materials used to transport water.
Generally a naturally occurring phenomenon, hardness is a measure of the
calcium and magnesium salts dissolved in the water. Hardness levels of less
than 200 milligrams per litre (expressed as a concentration of calcium
carbonate) are described as good quality water in the Australian Drinking
Water Guidelines.
50
On the basis of taste, a concentration of total dissolved solids of less than
500mg/L is also described as good quality water in the Australian Drinking
Water Guidelines.
Sometimes, domestic plumbing can be a source of elevated levels of copper or
iron measured at the tap. Copper in drinking water can have health effects.
Plumbing can also be a source of lead in drinking water.
Several elements are essential to human nutrition at low doses, yet can have
negative effects at high doses. These include arsenic, selenium, chromium,
copper, molybdenum, nickel, zinc and sodium. The elements lead, arsenic and
cadmium are suspected carcinogens.
A summary of the scientific evidence that the guideline values for these and
other chemicals are based upon can be found in the Australian Drinking Water
Guidelines.
Organic chemicals in water
Organic chemicals in water derive from:
• The breakdown of naturally occurring organic materials.
• Contamination of source water.
• Reactions that take place during water treatment and distribution.
The breakdown of naturally occurring organic materials is the predominant
source of organic chemicals in water. These chemicals are derived from
vegetation, soil humus, and microbiological activity. Water scientists refer to
this material as natural organic matter (or NOM). These organics are typically
benign, although they can be responsible for such aesthetic problems as colour,
taste and odour.
Excessive algal growth in source waters can lead to the tainting of drinking
water supplies with complex and unpleasantly scented organic components such
as geosmin and methylisoborneol.
The toxins produced by some blue-green algae – or cyanobacteria – are an
exception to the usually benign character of NOM. These toxins are harmful to
human health.
Cyanobacteria
51
A wide range of organic substances can enter the water source from human
activities in the catchment. These sources include agriculture, runoff from urban
settlements, wastewater discharge and leachate from contaminated soils. Most
organics in water supplies that have harmful health effects are part of this group.
They include pesticides and solvents.
Organic contaminants formed during water treatment include disinfection
byproducts formed, for example, when chlorine reacts with natural organic
matter.
Disinfection byproducts
Disinfection of water, using treatment methods such as chlorination, has
removed the threat of waterborne epidemics and reduced infant mortality rates
to very low levels in Australia. Without disinfection, Australians would still be
at risk from diseases such as cholera.
However, there is a downside to disinfection; the use of oxidants for
disinfection, taste, odour and colour removal can produce undesirable organic
byproducts.
During chlorination of water supplies, the chlorine reacts not only with the
microorganisms but also with most of the other organic material present in the
water, either dissolved or in suspension. This produces a range of organic
compounds known as disinfection byproducts. The presence of these
compounds has been detected only as more and more sensitive scientific
equipment has been developed.
These disinfection byproducts contain halogens, a group of elements with
similar chemical properties. These halogens are fluorine, chlorine, bromine and
iodine. While a lot remains to be known about many of these disinfection
byproducts, they include a group of chemicals called trihalomethanes (THMs),
mainly chloroform (trichloromethane), plus a broad range of other compounds
including haloacetic acids, halonitriles, haloaldehydes and chlorophenols.
In order to keep the level of disinfection byproducts low in the water supply,
treatment of raw waters is carried out to remove as much NOM as possible
before disinfection. Less NOM means there is less material to form disinfection
byproducts and also less chlorine is required to achieve adequate disinfection of
the water supply.
Several epidemiological studies have indicated a possible association between
chlorinated drinking water and increased risks from a variety of cancers, mainly
52
to do with the bladder, colon and rectum. However, other studies have not found
such associations. Therefore, because of the limitations of the data, no definite
conclusions can be based on these studies.
Alternative disinfectants – chloramines, chlorine dioxide and ozone – can also
react with organic matter in source water to produce disinfection byproducts.
The byproducts from these reactions are also not widely understood.
The Australian Drinking Water Guidelines suggest guideline values for a
range of disinfection byproducts.
53
WATER REGULATIONS, GUIDELINES AND STANDARDS
While Australia has national drinking water guidelines prepared by a joint
committee of the National Health and Medical Research Council (NHMRC) and
the Agriculture and Resource Management Council of Australia and New
Zealand (ARMCANZ), regulation of drinking water is a matter for each state
and territory.
Under Australia’s constitutional arrangements, public health and natural
resource management, including water, are largely state or territory
responsibilities. Therefore, the government of the particular state or territory
decides whether and how the latest Australian Drinking Water Guidelines,
World Health Organization (WHO) Guidelines for Drinking Water Quality or
some other guidelines are to be implemented.
Protection of public health is the most important factor for state and territory
governments to consider but other factors, such as the views of consumers, are
also very important. Indeed, community consultation is discussed in detail in the
Australian Drinking Water Guidelines.
Generally speaking, drinking water quality has not been subject to specific
legislation in Australia. However, other means have been used to require the
water supply to meet particular standards. These include operating licences,
charters, memoranda of understanding and customer contracts.
The Australian water industry is expected to provide supplies that are safe for
the community at large, including infants and the aged who are more at risk
from waterborne infection than most.
Some people have special needs that may make them particularly vulnerable to
infection, including waterborne infection, for example immunocompromised
persons. In these circumstances medical advice should be sought as to any
possible risk associated with consuming tap water.
Some medical and industrial processes have water quality requirements that are
more stringent than those for drinking water. For example, some require water
to be sterile, that is free of all microorganisms, or require the complete absence
of dissolved salts. Mains water usually contains microorganisms from the
biofilm that develop on the inside surface of the water main. It always contains
some level of naturally occurring dissolved matter.
54
ASSURING QUALITY
Since their first publication in 1987, the Australian Drinking Water Guidelines
have provided advice to drinking water suppliers on management of their
systems and encouraged the adoption of quality systems.
In recent years, the division of responsibilities between various agencies, and in
particular the transfer of catchment and water resource management to agencies
other than drinking water suppliers, has made it more important for water
suppliers to have formal processes for assuring the quality of drinking water.
The range of agencies involved in individual water supply systems can be large.
Water resource departments, natural resource and environment departments,
agriculture departments, local governments, planning authorities, catchment
water management boards, and community-based interest groups and
organisations can all have a role in ensuring water quality.
In some cases, restructuring of responsibilities has also extended to dividing the
traditional functions associated with drinking water supply, with separate
agencies being responsible for bulk water supply, water treatment and water
reticulation.
Clear agreements between agencies are necessary to provide safe and pleasant
drinking water. Responsibility for water extends beyond the drinking water
supplier and requires collaboration and consultation with other agencies.
Ultimately, however, it is the drinking water suppliers that are responsible for
the delivery of safe drinking water to consumers.
There has been an increasing trend for Australian water authorities to adopt
quality systems including ISO 9001 (Quality Management), ISO 14001
(Environmental Management), AS/NZS 4360 (Risk Management) or Hazard
Analysis and Critical Control Point (HACCP).
These available systems provide generic requirements for organisations
undertaking a diverse range of activities, but it was recognised that they may
have some limitations in their applicability to the management of drinking water
quality.
Therefore, during the most recent revision of the Australian Drinking Water
Guidelines, a comprehensive Framework for the Management of Drinking
Water Quality was developed to address the specific challenges of drinking
water supply. The Framework provides guidance on the design of a structured
55
and systematic approach for the management of drinking water quality from
catchment to consumer, to assure its safety and reliability.
The Framework incorporates a preventive risk management approach; it
includes elements of HACCP, ISO 9001 and AS/NZS 4360, but applies them in
a drinking water supply context to support consistent and comprehensive
implementation by suppliers.
The Framework addresses four general areas:
• Commitment to drinking water quality management. This involves
developing a commitment to drinking water quality management within the
organisation. Adoption of the philosophy of the Framework is not sufficient in
itself to ensure its effectiveness and continual improvement. Successful
implementation requires the active participation of senior executive and a
supportive organisational philosophy.
• System analysis and management. This involves understanding the entire
water supply system, the hazards and events that can compromise drinking
water quality, and the preventive measures and operational control necessary for
assuring safe and reliable drinking water.
• Supporting requirements. These requirements include basic elements of
good practice such as employee training, community involvement, research and
development, validation of process efficacy, and systems for documentation and
reporting.
• Review. This includes evaluation and audit processes and their review by
senior executive to ensure that management system is functioning satisfactorily.
These components provide a basis for review and continual improvement.
For more information on the Framework, consult the Australian Drinking Water
Guidelines (http:/www.nhmrc.gov.au/publications/synopses/eh19syn.htm).
56
WATER AND PUBLIC POLICY
Overview
It was intended by those drafting the Constitution of the Commonwealth of
Australia at the close of the 19th century that natural resource policy, including
that relating to water, would remain a responsibility of the States.
In fact, one section of the Constitution specifically restricts the role of the
Commonwealth in relation to water.
Towards the close of the 20th century that remained largely the case, although
the legal position has become less clear as a result of decisions by the High
Court.
100. The Commonwealth shall not, by any law or regulation of trade or
commerce, abridge the right of a State or of the residents therein to the
reasonable use of the waters of rivers for conservation or irrigation.
However, the Commonwealth Government has the capacity to indirectly
influence any area of public policy in Australia.
In relation to water, the Commonwealth has acquired an important role in policy
development in recent years.
Given the increasing commercialisation and private sector involvement in the
water industry, the option remains for the Commonwealth to explore the extent
of its direct powers under the Constitution. However, the path being followed in
the development of national policy and a regulatory framework in this area, as
in others, is one of cooperation with the State and Territory governments.
In 1994 the Council of Australian Governments (COAG) agreed on a Water
Reform Agenda to work towards reform in the water industry at the national
level. More recently, in 2004, this was succeeded by the formation of the
National Water Commission and adoption of the National Water Initiative
(NWI). The NWI represents the Australian Government’s and state and territory
governments’ shared commitment to water reform in recognition of:
57
•
the continuing national imperative to increase the productivity and
efficiency of Australia’s water use;
•
the need to service rural and urban communities; and
•
ensuring the health of river and groundwater systems, including by
establishing clear pathways to return all systems to environmentally
sustainable levels of extraction.
National Water Commission website (http://www.nwc.gov.au/index.cfm)
The National Water Quality Management Strategy is also a national initiative
aimed at developing guidelines to assist regulation of public health and the
environment. Australian Drinking Water Guidelines fits within the umbrella of
the National Water Quality Management Strategy.
At the level of the individual States and Territories, commercial pressures from
within Australia and from overseas have also produced changes in the way
water services are delivered.
Commercialisation and corporatisation of many Australian urban water
businesses has led to management responsibilities being vested in commercial
boards, in contrast to earlier arrangements where services were provided
directly by an arm of government. Now the role of board members is to provide
significant commercial skill and focus, as well as to buffer the organisation
from extraneous political involvement.
Competition for inputs to the water industry in Australia is well developed with
outsourcing and Build Own Operate (BOO) and Transfer (BOOT) contracts for
major treatment plants completed and currently in operation.
Another recent development in the water industry in Australia has been the
growing involvement of large international water companies.
Who is supplying the water now?
In Queensland, New South Wales and Tasmania, local government has long had
a key role in the provision of water services. This remains the case. In the other
states and territories, various other arrangements have evolved.
In Sydney, a catchment authority (Sydney Catchment Authority) has been
established to work with the government-owned corporation that formerly had
total responsibility for the city’s water supply (Sydney Water Corporation) but
58
remains responsible for water distribution and wastewater services. Sydney
Water Corporation services a population of four million.
In Melbourne, three government-owned companies (City West Water Ltd.,
South East Water Ltd., and Yarra Valley Water Ltd.) are the retailers and the
wholesaler is a government-owned corporation (Melbourne Water Corporation).
The wholesaler also controls the catchment for most of its supply.
In Adelaide, a privately owned water company (United Water International Pty.
Ltd.) provides water services under an agreement with the government authority
(South Australian Water Corporation).
The Water Corporation is a government-owned corporation that provides urban
water services in Perth, and in most of Western Australia.
In Canberra, and the ACT generally, a public-private multi-utility partnership
now provides services (ActewAGL).
A government-owned multi-utility (Power and Water Corporation) provides
services to the larger and less remote communities in the Northern Territory,
including Alice Springs and Darwin.
Brisbane is an example of local government in a major Australian city providing
water services (Brisbane City Council). Bulk water is supplied to Brisbane and
neighbouring councils by South East Queensland Water Corporation.
Most organisations providing urban water services in Australia have
experienced some degree of structural reform in recent years, which has
clarified accountabilities by separating policy, regulatory and commercial
(operational) functions. The accepted wisdom is that this separation provides
urban water businesses with clear commercial goals of customer service, while
safeguarding public health and achieving environmental compliance in a sound
business operation, free of other conflicting objectives.
Community Consultation
The COAG Water Reform Agenda, agreed in 1994, adopted the principle of
public consultation by government agencies and service providers when change
and/or new initiatives were being contemplated involving water resources.
Subsequently the Australian Drinking Water Guidelines emphasised the right
of communities to participate in the development of policies relating to their
water supply.
59
“The ADWG are intended to provide consumers with safe and aesthetically
pleasing water and ultimately it is consumers who will be the final judges of
water quality. It is vitally important that consumers are viewed as active
partners in making decisions about drinking water quality and the levels of
service to be adopted. Community expectations and willingness to pay must be
considered.”
Australian Drinking Water Guidelines
The Guidelines also provide advice on how customers should be involved in
considering options for effective and acceptable monitoring and reporting on
performance of their water supply, and on the frequency of such reporting.
The COAG Water Reform Agenda also mentions the need for the public to be
informed of the cause and effect relationship between infrastructure
performance, standards of service and related costs, with a view to promoting
levels of service that represent the best value for money to the community.
The direction that community consultation on drinking water supplies will take
is difficult to predict. State and territory governments determine policy within
their jurisdiction, usually with a measure of community and industry
consultation and certainly with accountability for policy to Parliament and to
the electorate.
Community consultation is a process of mutual education. The community
learns what is involved with the development of a drinking water quality
program and water businesses learn about the “grassroots” issues.
Ideally, public involvement brings people together with different needs and
values to develop a plan for the “common good” through respectful dialogue.
Public interest groups bring key issues to the process.
The Australian Drinking Water Guidelines provide advice on public
consultation strategies and programs.
A fair price for water
In Australia, most water businesses have changed from a charging system based
largely on property value to one based on actual water consumed (a user-pays
policy). This reflects the major change in the philosophy contained in the
COAG Water Reform Agenda.
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Hunter Water in the Newcastle area of New South Wales pioneered this policy
in Australia in the 1980s and reported a fall in household water consumption of
30 per cent over previous trends. Even before the COAG decision, this
experience encouraged other water authorities to adopt the policy with a view to
managing demand for water.
The user-pays system gives the right economic signals to consumers about the
real value of this dwindling resource and encourages people to make more
efficient use of water.
However, low-income households in Australia spend in proportional terms
much more on utility services than high-income households. The implication is
that increases in the price of utility services, if not accompanied by other
compensation, will have a regressive and disproportionately negative impact on
low-income households. This is an issue for governments to consider.
Currently in Australia, the COAG-initiated industry reforms have led to waterpricing structures based on a tariff comprising:
• A fixed charge reflecting the cost of the service provision.
• A variable charge based on the volume of water purchased.
Demand management and water conservation
The term “demand management” can be defined as any regulatory, policy,
technical, service or commercial interaction with customers or consumers that
enables volumes to be managed to minimise economic costs and environmental
impacts to society.
Demand management measures to ensure consumers use less water have
included advertising, education, pricing and appliance redesign.
Some current approaches to demand management include:
• Improved information for customers on water-saving devices.
• Promotion of the National Water Conservation Labelling (AAA) Scheme.
• Information for homeowners and gardeners on more efficient watering
practices and irrigation systems.
• Provision of information on low water-use gardens, plants and shrubs.
• More efficient watering of public open space.
61
• Integrated and coordinated planning involving all agencies with an interest in
water-related issues.
• Water and energy efficiency in the planning, design and construction of
homes and buildings.
Further information can be obtained at www.savewater.com.au
Encouraging the use of alternatives to conventional surface and groundwater
harvesting can also be regarded as a form of demand management. These
alternatives include stormwater, effluent reuse, rainwater tanks and greywater
use. As always, pricing plays an important part in weighing up these options.
How do the costs of these alternative sources of water compare with the
construction of new reservoirs? Producing a non-potable water supply (for
example, garden and fire use only) from some of the above sources involves
significant treatment and cost.
Water restrictions
Some water businesses in Australia have opted for restrictions on water use to
conserve water supplies and minimise capital expenditure.
Restrictions can enable construction of expensive major storage reservoirs to be
deferred for many years. By developing a series of restriction levels, depending
on remaining storage capacity, the maximum daily consumption can be curbed
during drought periods.
Following a community consultation process, community endorsement should
be obtained for such a policy.
62
Several water authorities in very hot and dry regions of Australia have adopted a
cooperative policy with consumers to restrict peak water usage on very hot days
or to restrict garden watering to periods in which it is more effective.
In the Victorian rural city of Mildura and several other large towns serviced by
Lower Murray Water, only hand-held hoses may be used (that is, there is a ban
on fixed sprinklers) between 10am and 10pm when the forecast temperature is
39 degrees C or above. On average, this applies about 14 days a year.
Perth, Western Australia has a permanent ban on sprinkler use between 9 am
and 6 pm. The Water Corporation introduced the ban several years ago due to
low storage in its dams. It has been retained since then as a water conservation
measure.
Melbourne, Victoria has also introduced permanent water saving rules including
restrictions on garden watering systems, a ban on hosing paved areas, and
permit requirements for filling new swimming pools.
63
WATER IN THE FUTURE
Addressing tomorrow’s problems
Just as issues around water have moulded much of Australia’s past, they will
also influence the future. Several issues threaten to impact strongly on water
resources and urban supplies in Australia in the future. These include climate
change due to global warming, salinity and environmental degradation
generally.
Increasingly, communities are asking questions about basic quality of life
issues, such as their water supply. They have a right to ask these questions, and
to expect answers, just as they have a right to expect the drinking water
available to their children to be safe and pleasant.
The needs of the population in the next 30 to 50 years are uncertain. Demand
management programs will help to halt the previous trend of increasing percapita consumption.
The optimum population of Australia has been the subject of speculation and
debate by governments, academics and the community for decades. In recent
times, the term ecologically sustainable development has been used when
estimating limiting conditions on population growth. Issues such as the impact
of increasing urban development on the environment and on quality of life need
to be included in those discussions.
Water supply, use and disposal did not undergo major technological changes in
the last century: there were no paradigm shifts in relation to technology of water
management. In the 21st century, technology is likely to provide much more
change for the water supply industry.
Increased use of water-efficient appliances by urban consumers will play a part
in achieving ecologically sustainable development. A water-efficient appliance
is one that has water conservation as one of its design criteria. It uses or enables
the use of water more efficiently.
Water-efficient appliances generally do not rely on attitudes or behaviour of the
user; rather, they impose responsible water use on the user. Savings from waterefficient appliances take time, because they are introduced slowly, replacing
existing appliances. However, the water-efficient appliances being promoted at
this time are expected to lead to a significant fall in per capita water use over the
next couple of decades.
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Climate change
According to CSIRO’s latest climate change estimates, Australia will become
hotter and drier in coming decades. Warmer conditions will produce more
extremely hot days and fewer cold days. CSIRO scientists estimate that over
most of the continent, average temperatures will be 0.4 to two degrees C greater
in 2030 than 1990. By 2070, average temperatures are likely to increase one to
six degrees C. These temperature ranges reflect the scientific uncertainty
associated with the projections.
CSIRO climate projections indicate that the warming won’t be the same
everywhere, with slightly less warming in some coastal areas and Tasmania,
and slightly more warming in the north-west.
South-western Australia can expect decreases in rainfall, as can parts of southeastern Australia and Queensland. Wetter conditions are possible in northern
and eastern Australia in summer and inland Australia in autumn.
In areas that experience little change or an increase in average rainfall, more
frequent or heavier downpours are likely. Conversely, more dry spells are likely
in regions where average rainfall decreases.
Evaporation is expected to increase over most of the country. When combined
with expected changes in rainfall, there will be a clear decrease in available
moisture across the country.
Governments and water authorities have to consider climate change now in
planning water supplies for the future.
Environmental degradation
Significant deforestation has occurred in Australia since British colonisation in
1788. One result of this change in vegetative cover, affecting transpiration rates
from forests, has been a reduction in rainfall in some catchments. Another has
been salinity. A wide understanding of the need to reverse previous land
management practices now exists, but in some areas it may be too late.
Across the country we need to find a meaningful balance between the
competing demands for water of agriculture, urban consumption, and
ecosystems.
65
One action to help achieve this balance was the establishment by the Federal
Government of the National Land and Water Resources Audit. The Audit
recently produced Australian Water Resources Assessment 2000 – surface and
groundwater availability and quality, the first comprehensive national audit of
Australia’s surface water and groundwater resources covering both water
quantity and water quality.
The Audit reveals that, on average, Australia’s water use has increased 65 per
cent since the early 1980s.
Using the best available information provided by state and territory agencies,
the Audit shows that 26 per cent of Australia’s surface water management areas
are approaching or beyond sustainable extraction limits and that 34 per cent of
Australia’s groundwater management units are approaching or beyond
sustainable extraction limits.
Further information on the Audit is available on the Internet
(www.nlwra.gov.au)
Salinity
Changes to the Australian landscape, and in particular tree clearing, have
resulted in the widespread and rapidly growing problem of salinity. While
naturally occurring salinity is part of the Australian landscape, human impacts
have upset the previously existing balance.
The problem has developed slowly. With the removal of the natural vegetation,
the amount of water entering the water table (called the recharge) has increased
and the rising groundwater level has dissolved the accumulated salt within the
soil. Eventually, and perhaps more than 100 years later, the groundwater level
reaches the surface, bringing the salt with it. This results in the death of all but
the most salt-tolerant plants with consequential changes to other parts of the
ecosystem.
While farmers were among the first to be affected, through salt-affected
agricultural land, the impact on sources of freshwater has also been of growing
significance.
Biodiversity, as well as regional and urban infrastructure, such as water supply,
roads and buildings are now also at risk.
66
Just as it has taken a long time to appreciate the scale of the environmental
degradation, the timeframe for these changes to be slowed or reversed will also
be considerable.
The cost of the problem to the wider Australian community will be huge.
A comprehensive national assessment of the problem, Australian Dryland
Salinity Assessment 2000, has recently been undertaken and a plan for tackling
it has been developed. The National Land and Water Resources Audit has
undertaken this work. Full details are available on the Internet
(www.nlwra.gov.au).
According to a statement issued by the Prime Minister in October 2000 at the
launch of the National Action Plan for Salinity and Water Quality in Australia,
salinity and water quality problems were critical and demanded urgent attention.
Among the problems detailed by the Prime Minister were:
• One-third of Australian rivers are in an extremely poor condition.
• Adelaide’s drinking water is likely to fail World Health Organization
salinity standards in two days out of five within 20 years.
• Land and water degradation, excluding weeds and pests, is costing up to
$3.5 billion a year.
For more details see the National Action Plan for Salinity and Water Quality
website (http://www.napswq.gov.au/).
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GLOSSARY OF WATER-RELATED TERMS
A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V
-W - X - Y - Z
A
absorption: The physical uptake of water and any material dissolved in it.
acidic: Describing the chemical characteristic of acid. Technically, a pH value below seven.
activated carbon: Particles or granules of carbon used in water treatment because of their
high capacity to selectively remove certain trace and soluble materials. Usually obtained by
heating a carbon source (such as wood).
acute: Occurring immediately or in a short period of time (that is within hours or days); used
to describe health effects that are experienced shortly after an exposure has occurred. Also
see chronic.
adsorption: A process in which molecules are attracted to and retained on a surface
(compare with absorption). In water treatment, the large surface area of activated carbon is
used to remove low concentrations of contaminants.
aeration: The mixing of air and water, resulting in oxygen from the air dissolving in the
water.
aerobic: As applied to water, refers to the presence of oxygen dissolved from the air (also see
anaerobic).
algae: Microscopic plants which contain chlorophyll and live floating or suspended in water.
They may also be attached to structures, rocks or other submerged surfaces. Excess algal
growths can give tastes and odours to drinking water. Algae produce oxygen when exposed
to sunlight and use oxygen in darkness. Their biological activities significantly affect the pH
and dissolved oxygen concentrations of water.
algal bloom: The occurrence of a high concentration of microscopic plant life, such as green
or blue-green algae (cyanobacteria), in a river, lake and reservoir, usually as a result of
increased nutrient content.
alkaline: Describing the chemical characteristic that can neutralise acid. Technically, a pH
value above seven.
anaerobic: As applied to water, refers to the absence of oxygen (also see aerobic).
ANCOLD: The Australian National Committee on Large Dams Incorporated (ANCOLD
Inc) is an incorporated voluntary association of organisations and individual professionals
68
with an interest in dams in Australia. Members include local, state and federal agencies, dam
owners and operators, contractors, consultants and academics.
ANZECC: Australian and New Zealand Environment and Conservation Council. The
members of the Council are the relevant government ministers from the various jurisdictions.
aquatic: Plant or animal life living in, growing in, or adapted to water.
aquifer: Soil or rock below the land surface that is saturated with water. A confined aquifer
has layers of impermeable material above and below it and is under pressure. When the
aquifer is penetrated by a well, the water rises above the top of the aquifer. In an unconfined
aquifer, the upper water surface (water table) is at atmospheric pressure and thus is able to
rise and fall.
ARMCANZ: Agriculture and Resource Management Council of Australia and New Zealand.
The members of the Council are the relevant government ministers from the various
jurisdictions.
artesian well: A well bored down to the point, usually at great depth, at which the water
pressure is so great that the water is forced out at the surface.
Australian Drinking Water Guidelines: The key Australian reference to drinking water
quality published by the National Health and Medical Research Council (NHMRC) and the
Agriculture and Resource Management Council of Australia and New Zealand
(ARMCANZ).
B
backflow: A reverse flow condition, created by a difference in water pressures, which causes
water to flow back into the distribution pipes of a potable water supply from any source or
sources other than an intended source. Also see cross-connection.
backwashing: In water treatment, the process of reversing the flow of water back through the
filter media to remove the entrapped solids.
bacteria: Singular: bacterium. Microscopic single-celled organisms with rigid walls. Bacteria
are found almost everywhere. Some bacteria in soil, water or air can cause human disease.
blue-green algae: See cyanobacteria.
C
capillary action: The movement of water through very small spaces due to molecular forces.
carcinogen: Any substance that tends to produce cancer in an organism.
69
catchment: The areas of land which collect rainfall and contribute to surface water (streams,
rivers, wetlands) or to ground-water. A catchment is a natural drainage area, bounded by
sloping ground, hills or mountains, from which water flows to a low point.
chloroform: A volatile organic compound formed as a byproduct of chlorination of natural
waters. One of several compounds referred to as trihalomethanes. See disinfection
byproducts.
chloramines: Compounds formed by the reaction of hypochlorous acid (or aqueous chlorine)
with ammonia. Used to disinfect water supplies.
chlorination: The application of chlorine to water, generally for the purpose of disinfection.
chlorinator: A mechanical device which is used to add chlorine to water.
chronic: Occurring over a long period of time, either continuously or intermittently; used to
describe ongoing effects that develop only after a long exposure, especially when referring to
health (contrast with acute).
coagulant: Chemical used to coagulate · clump together · very fine particles into larger
particles. Soluble salts of aluminium and ferric iron are the most commonly used coagulants
in water treatment.
coagulation: The clumping together of very fine particles into larger particles caused by the
use of chemicals (coagulants). The chemicals neutralise the electrical charges of the fine
particles and destabilise the particles. This clumping together makes it easier to separate the
solids from the water by settling, skimming, draining, or filtering.
coliform: A group of bacteria found in the intestines of animals (including humans) and also
in soil, vegetation and water.
colloids: Very small, finely divided solids (particles that do not dissolve) that remain
dispersed in a liquid for a long time due to their small size and electrical charge. When most
of the particles in water have a negative electrical charge, they tend to repel each other. This
repulsion prevents the particles from clumping together, becoming heavier, and settling out.
condensation: The process of water vapour in the air turning into liquid water. Condensation
is the opposite of evaporation.
contaminant: Any physical, chemical, biological, or radiological substance or matter that has
an adverse effect.
CRC: Cooperative Research Centre.
cross connection: Any actual or potential connection between a drinking (potable) water
system and an unapproved water supply or other source of contamination.
CSIRO: Australia’s Commonwealth Scientific and Industrial Research Organisation.
70
cyanobacteria: A group of microorganisms with bacteria-like properties that can cause taste,
odour and other problems in water supplies. Also known as blue-green algae.
D
desalination: The removal of dissolved salts (such as sodium chloride) from water by
specific water treatment processes, for example reverse osmosis.
destratification: The development of vertical mixing within a lake or reservoir to remove
layers of temperature, plant, or animal life. This vertical mixing can be achieved by
mechanical means (pumps) or through the use of diffusers that release air into the lower
layers of the water body.
disinfection: The process designed to kill most microorganisms in water, including
essentially all pathogens.
disinfection byproduct: A compound formed by the reaction of a disinfectant, such as
chlorine, with organic material in the water supply.
distribution system: A network of pipes leading from a water treatment plant to customers·
plumbing systems.
dose-response: The quantitative relationship between the dose of an agent and an effect
caused by the agent.
drainage basin: Land area where rain runs off into streams, rivers, lakes, and reservoirs. It is
a land feature that can be identified by tracing a line along the highest elevations between two
areas on a map, often a ridge. Also see catchment.
drinking water supplier: An organisation, agency or company that has responsibility and
authority for treating and/or supplying drinking water.
drinking water supply system / water supply system: All aspects from the point of
collection of water to the consumer. It can include catchments, ground-water systems, source
waters, storage reservoirs and intakes, treatment systems, service reservoirs and distribution
systems, and consumers plumbing.
E
effluent: Flow leaving a place or process. Sewage effluent refers to the flow leaving a
sewage treatment process.
endemic: Something found in a particular people or location, such as a disease which is
always present in the population.
enterovirus: A group of viruses that may infect the gastrointestinal tract of humans and
animals. The presence of enteroviruses in water may indicate contamination.
71
epidemic: Widespread outbreak of a disease, or a large number of cases of a disease in a
single community or relatively small area. Disease may spread from person to person, and/or
by the exposure of many persons to a single source, such as a water supply.
epidemiology: A branch of medicine which studies the patterns of diseases in populations,
and their causes. The objective of epidemiology is to understand how and why diseases occur
so that ways can be developed to prevent or reduce disease.
epilimnion: The upper layer of water in a thermally stratified lake or reservoir. This layer
consists of the warmest water and has a fairly uniform (constant) temperature. The layer is
readily mixed by wind action.
eutrophication: The increase in the nutrient levels of a lake or other body of water. This
usually causes an increase in the growth of aquatic animal and plant life.
evaporation: The process by which water or another liquid becomes a gas. Water from land
areas, bodies of water, and all other moist surfaces is absorbed into the atmosphere as a
vapour.
evapotranspiration: The combined processes of evaporation and transpiration.
exposure: Contact of a chemical, physical or biological agent with the outer boundary of an
organism, for example inhalation, ingestion or contact with the skin.
F
faecal coliform: A subgroup of bacteria of the coliform type that live mainly in the gut of
warm-blooded animals. The detection of faecal coliforms in water is an indication of poor
water quality and the possibility of pathogenic organisms being present.
facultative: As applied to bacteria, can grow under aerobic or anaerobic conditions.
filtration: A process for removing particles from water by passage through porous media.
flagellates: Microorganisms that move by the action of tail-like projections.
flocculation: The gathering together of fine particles in water by gentle mixing after the
addition of coagulant chemicals to form larger particles.
fluoridation: The addition of a chemical to increase the concentration of fluoride ions in
drinking water to a predetermined optimum limit to reduce the incidence of tooth decay in
children.
flushing: A method used to clean water distribution lines. Hydrants are opened and water
with a high velocity flows through the pipes and removes deposits from them.
G
72
gastroenteritis: An inflammation of the stomach and intestine resulting in diarrhoea, with
vomiting and cramps when irritation is excessive. When caused by an infectious agent, it is
often associated with fever.
geosmin: Earthy-musty-smelling compound affecting the taste and odour of water. Released
by blue-green algae (cyanobacteria).
Giardia lamblia: a protozoan pathogen that can cause gastroenteritis (called giardiasis) if
ingested. The infective form , known as a cyst, is shed in the faeces of people and animals.
Great Artesian Basin: Largest artesian ground-water basin in the world. It underlies
approximately one-fifth of Australia and extends beneath the arid and semi-arid parts of
Queensland, New South Wales, South Australia and the Northern Territory, stretching from
the Great Dividing Range to the Lake Eyre depression. The Basin covers a total area of more
than 1.7 million square kilometres and has an estimated water storage of 8,700 million
megalitres.
greywater: Wastewater from clothes washing machines, showers, bathtubs, hand washing,
and sinks.
ground-water: The supply of fresh water found beneath the Earth’s surface, usually in
aquifers.
guideline value: The concentration or measure of a water quality characteristic that, based on
present knowledge, does not result in any significant risk to the health of the consumer
(health-related guideline value), or is associated with good quality water (aesthetic guideline
value). See Australian Drinking Water Guidelines.
H
halogen: One of the chemical elements chlorine, bromine, or iodine.
hard water: Alkaline water containing dissolved salts that interfere with some industrial
processes and prevent soap from lathering. The hardness of water is usually expressed as the
equivalent concentration of calcium carbonate in milligrams per litre.
hazard: A biological, chemical or physical agent that has the potential to cause harm or loss.
Hazard Analysis and Critical Control Point (HACCP): A systematic methodology to
control hazards in a process by applying a two-part technique: first, an analysis that identifies
hazards and their severity and likelihood of occurrence; and second, identification of critical
points where the hazards may be controlled, and the monitoring criteria to ensure that
controls are working effectively. This system was introduced in the food industry and is now
being applied in the Australian water industry to drinking water.
head loss: The pressure lost by water flowing in a pipe or channel as a result of turbulence
caused by the velocity of flowing water and the roughness of the pipe, channel walls or
restrictions caused by fittings.
73
headworks: Infrastructure at the water source, where water enters the distribution system.
heavy metals: Metallic elements with high atomic weights, for example, mercury,
chromium, cadmium, arsenic, and lead. These elements can damage living things at low
concentrations and tend to accumulate in the food chain.
herbicide: A compound, usually a synthetic organic chemical, used to kill or control plant
growth.
heterotrophic plate count: A method for measuring the number of bacteria in a water
sample able to grow on a simple organic medium.
humus: Organic portion of the soil remaining after prolonged microbial decomposition.
hydrology: The study of the occurrence, distribution and circulation of the natural waters of
the earth.
hypochlorite: Chemical compounds containing available chlorine; used for disinfection.
They are available as liquids (bleach) or solids (powder, granules and pellets).
hypolimnion: The lowest layer in a thermally stratified lake or reservoir. This stagnant layer
of colder, more dense water, has a constant temperature.
I
infrastructure: Services and equipment needed to support urban communities, generally
including water supply, stormwater and waste treatment facilities, electricity, telephones,
roads and community services required for residential, commercial and industrial activities.
inorganic: Material such as sand, salt, iron, calcium salts and other mineral materials.
Inorganic substances are of mineral origin. Also see organic.
integrated catchment management (ICM): The coordinated planning, use and management
of water, land, vegetation and other natural resources on a river or ground-water catchment
basis. ICM is based on cooperation between community groups and government agencies to
consider all aspects of catchment management.
invertebrate: An organism without a backbone.
ion: An atom or group of atoms which has gained or lost electrons and carries an electric
charge.
ISO 9001:1994 (Quality Systems): An international accredited standard that provides a
generic framework for quality systems. Designed to assure conformance to specified
requirements by a supplier at all stages during the design, development, production,
installation, and servicing of a product. It sets out the requirements for an organisation to
guarantee a consistent end product.
74
ISO 14001:1996 (Environmental Management Systems): An international accredited
standard that provides a generic framework for guidance on the development and
implementation of an environmental management system to minimise the impacts of business
operations on the environment and to foster environmental sustainability.
L
leaching: The process by which soluble materials in soil, such as salts, nutrients, pesticide
chemicals or contaminants, are washed into a lower layer of soil or are dissolved and carried
away by water.
leachate: Solution containing dissolved substances as a result of rainwater percolating
through soil or similar material.
log or logarithm: Mathematical concept which forms the basis for the pH scale.
M
mains: Large underground water or sewer pipes.
malignant: Very dangerous or harmful, causing or likely to cause death.
metabolism: The sum of the chemical reactions occurring within a cell or a whole organism.
methylisoborneol: Earthy-musty-smelling compound affecting the taste and odour of water.
Released by blue-green algae (cyanobacteria).
microbial growth: Growth of microorganisms such as bacteria, algae, diatoms, plankton and
fungi.
microgram per litre (·g/L): A measure of concentration of a dissolved substance. One
microgram of a substance dissolved in each litre of water. This unit is equal to parts per
billion (ppb) since one litre of water weighs one billion microgram.
micron (·m) : A unit of length. One millionth of a metre or one thousandth of a millimetre.
microorganisms: Living organisms that can be seen individually only with the aid of a
microscope.
milligram per litre (mg/L): A measure of concentration of a dissolved substance. One
milligram of a substance dissolved in each litre of water. This unit is equal to parts per
million (ppm) since one litre of water weighs one million milligram.
mineralisation: The microbial conversion of an element from an organic to an inorganic
state.
molecular weight: The molecular weight of a compound is the sum of the atomic weights of
all of the elements in the compound.
75
mutagen: An agent that causes a permanent genetic change in a cell, that is change to the
DNA, other than that which occurs during normal genetic recombination.
N
NOM: Natural organic matter. Usually responsible for any brown discolouration in water.
NTU: Nephelometric turbidity unit. The unit of measure for turbidity.
neurotoxicity: Exerting a destructive or poisonous effect on nerve tissue.
NHMRC: National Health and Medical Research Council. A major source of health policy
advise for Australian governments.
nitrification: The biochemical transformation of ammonium nitrogen to nitrate nitrogen.
non-potable: Water that is considered unsafe and/or unpalatable for drinking.
nutrient: Any substance that is assimilated (taken in) by organisms and promotes growth.
O
organic: Substances that come from animal or plant sources. Organic substances always
contain carbon. Also see inorganic.
osmosis: The passage of a liquid from a weak solution to a more concentrated solution across
a semipermeable membrane. The membrane allows the passage of the solvent (water) but not
the dissolved solids (solutes). This process tends to equalize the conditions on either side of
the membrane. Also see reverse osmosis.
oxidation: The addition of oxygen, removal of hydrogen, or removal of electrons from an
element or compound. It is the opposite of reduction. In the environment, organic matter is
oxidized to more stable substances.
ozonation: The application of ozone to water for disinfection or for taste and odour control.
P
palatable: Palatable water is water of pleasing taste, odour and appearance.
parts per billion (ppb): A measurement of concentration on a weight or volume basis. This
term is equivalent to microgram per litre, the preferred term. Used to describe extremely
small concentrations.
parts per million (ppm): A measurement of concentration on a weight or volume basis. This
term is equivalent to milligram per litre (mg/L), the preferred term.
76
pathogen: A disease-causing microorganism; includes various types of bacteria, viruses,
fungi and protozoa.
pathology: The study of the effects of disease.
per capita use: The average amount (of water) used per person during a standard time
period, generally per day.
permeable: Can be passed through. Term used to describe soil and rock and also in
membrane technology.
permeability: In relation to ground-water, refers to the ability of soil or rock to transmit
water.
pesticide: Any substance or chemical designed or formulated to kill or control animal pests.
Also see herbicide.
pH: A measure of the basic (alkaline) or acidic condition of a solution. A pH of less than 7 is
acidic, of 7 is neutral and of more than 7 is alkaline. Natural waters usually have a pH
between 6.5 and 8.5.
photosynthesis: A process in which organisms, with the aid of chlorophyll (green plant
pigment), convert carbon dioxide and inorganic substances into oxygen and additional plant
material, using sunlight for energy. All green plants grow by this process.
phytoplankton: Small photosynthetic plant organisms in the aquatic environment.
porosity: In relation to ground-water, the capacity of soil or rock to hold water.
potable water: Water that is safe and satisfactory for drinking and cooking.
protozoa: Single-celled microscopic animal. Plural protozoa.
Q
quality: The totality of characteristics of an entity that bear on its ability to satisfy stated and
implied needs.
quality system: Organisational structure, procedures, processes and resources needed to
implement quality management (ISO 8402:1994).
R
radionuclide: Any man-made or natural element which emits radiation in the form of alpha
or beta particles, or as gamma rays.
77
raw water: Water in its natural state, before treatment; water entering the first treatment
process of a water treatment plant.
renal: Pertaining to the kidney.
reservoir: Any natural or artificial holding area used to store, regulate, or control water.
respiration: The process in which an organism uses oxygen for its life processes.
reverse osmosis: The application of pressure to a concentrated solution which causes the
passage of a liquid from the concentrated solution across a semipermeable membrane. The
membrane allows the passage of the solvent (water) but not the dissolved solids (solutes).
The liquid produced is demineralized water. Also see osmosis.
risk: The probability of a specified hazard causing harm.
risk management: The systematic evaluation of the water supply system, the identification
of hazards and hazardous events, the assessment of risks, and the development and
implementation of preventive strategies to manage the risks.
runoff: That portion of catchment rainfall which does not evaporate or infiltrate into the
ground but runs across the surface.
S
salinity: The concentration of dissolved salts, usually sodium chloride, in water.
sand filter: Device to remove suspended solids from water by passage through a bed of sand.
sanitary survey: An on-site assessment of the adequacy of the water sources, facilities,
equipment, operation, and maintenance of a public water systems for producing and
distributing safe drinking water.
sediment: Usually applied to material suspended in water or recently deposited from
suspension. In the plural the word is applied to all kinds of deposits from the waters of
streams, lakes, or seas.
sedimentation: A water treatment process in which solid particles settle out of the water
being treated in a large clarifier or sedimentation basin.
service pipe: A pipeline extending from the water main to the building served or to the
consumers system.
service reservoir/tank: A storage for drinking water generally within the distribution system
used to meet fluctuating demands, accommodate emergency requirements and/or equalise
operating pressures.
SODIS: Solar water disinfection. A water treatment process depending on solar energy only
to disinfect small quantities of water for use mainly at household level.
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soft water: Water having a low concentration of calcium and magnesium ions.
solvent: A substance that dissolves other substances, thus forming a solution. Water dissolves
more substances than any other, and is known as the universal solvent.
source water: See raw water.
Standards Australia: Previously the Standards Association of Australia but since 1 July
1999 Standards Australia International Limited has been a public company limited by
guarantee. The lead organization in Australia in the promotion, publication and acceptance of
standards for business and the community to increase efficiency and enhance product quality.
storage reservoir: A natural or artificial impoundment used to hold water before its
treatment and/or distribution.
stormwater: Technically, all runoff is stormwater. However, the term “stormwater” is
generally used in reference to urban runoff in constructed stormwater drainage systems.
stream: A general term for a body of flowing water; a natural water course containing water
at least part of the year. In hydrology, it is generally applied to water flowing in a natural
channel as distinct from a canal.
surface water: All water naturally open to the atmosphere (rivers, lakes, reservoirs, streams,
impoundments, seas, estuaries, etc.).
suspended solids: Solids that float on the surface or are suspended in water, and which are
largely removable by filtering.
T
thermocline: The middle layer in a thermally stratified lake or reservoir. In this layer there is
a rapid decrease in temperature with depth. Also called the metalimnion.
total dissolved solids (TDS): The concentration of dissolved solids in water. TDS is
measured on a sample of water that has passed through a very fine mesh filter to remove
suspended solids. The water passing through the filter is evaporated and the residue
represents the dissolved solids.
toxicity: The quality or degree of being poisonous or harmful to plant, animal or human life.
toxicology: Study of poisons, their effects, antidotes and detection.
transpiration: The process by which water vapour is released to the atmosphere by living
plants.
tributary: A smaller river or stream that flows into a larger river or stream. Usually, a
number of smaller tributaries merge to form a river.
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trihalomethane (THM): One of a family of organic compounds named as derivatives of
methane. THMs are found among the byproducts of chlorination of drinking water that
contains organic material.
turbidity: The cloudy appearance of water caused by the presence of suspended and
colloidal matter. The water quality parameter indicating the clarity of water.Turbidity is
measured by the amount of light that is reflected off particles in the water. It is measured by a
nephelometer in nephelometric turbidity units (NTU).
V
valve: A device that opens and closes to regulate the flow of water or other fluids.
vertebrate: Organisms that possess a backbone.
virus: A large group of infectious agents, much smaller than bacteria, that are able to be
viewed only through an electron microscope. They are not cells, but biologically active
particles that vary in size from 0.01 to 0.1 microns.
W
water cycle: The circulation of water on Earth as it evaporates from the sea and lakes,
condenses into clouds and falls again as precipitation (rain, hail, sleet, snow).
water quality: A description of the chemical, physical and biological characteristics of water
for a particular purpose.
water supplier: The owner or operator of a public water system.
watershed: See catchment.
water supply system: The collection, treatment, storage, and distribution of potable water
from source to consumer.
water table: The level of ground-water in an unconfined aquifer. This level can be very near
the surface of the ground or far below it.
Z
zoonoses: Diseases and infections that are naturally transmitted between vertebrate animals
and humans.
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APPENDIX 1
Why is Australia’s rainfall so variable?
Since the use of weather satellites began in the 1960s, great advances have been
made in understanding the world’s weather patterns. This has enabled scientists
to explain and even predict the cycles of droughts and floods that are so much a
feature of the weather pattern over much of Australia.
El Nino, La Nina and Southern Oscillation Index are terms used to describe a
major influence on this weather pattern.
El Nino refers to the extensive warming of the central and eastern Pacific Ocean
that leads to a major shift in weather patterns across the Pacific. In Australia,
and particularly in the eastern part of Australia, El Nino events are associated
with an increased probability of dry conditions. The most recent strong El Nino
event was 1997/98. Another weak to moderate event occurred in 2002/03,
causing major rainfall deficiencies across the country.
La Nina describes the reverse of the El Nino effect and is related to changes in
atmospheric conditions and ocean circulation. In Australia, and particularly in
the eastern part of Australia, La Nina events are associated with an increased
probability of wetter conditions. The most recent strong La Nina was 1988/89, a
much wetter than average season across much of Australia. A fairly weak La
Nina event occurred in late 1995 and early 1996, leading to conditions slightly
wetter than average in many areas. A moderate event occurred in 1998/99,
which weakened back to neutral conditions before forming again for a shorter
period in 1999 and ending in 2000.
The Southern Oscillation Index describes a key indicator of this weather pattern
based on measurements of atmospheric pressure. It is used to predict the
likelihood of extended very wet or very dry periods.
The El Nino phenomenon affects runoff in catchments serving all major
Australian water supply systems.
Detailed information about Australia’s climate and weather can be obtained
from the Bureau of Meteorology (http://www.bom.gov.au)
BACK
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Irrigation
Where sufficient low-cost water is available, irrigated agriculture is practised in
Australia. This activity is attracting increased attention from government policymakers as concern grows at the proportion of water flows taken from the
environment and at how efficiently water is used in irrigated agriculture.
In recent years, the irrigation industry has undergone major changes in the way
it is structured, in the way water is priced and with the use of market
mechanisms to reallocate resources to more productive uses. Efforts have also
been made to promote efficient and sustainable irrigation practices.
In the past, state governments have met the cost of establishing the irrigation
industry. The price structure for irrigation water is now moving to better reflect
the value of the resource.
It is difficult to provide a typical figure for the cost of water used in irrigated
agriculture because it is influenced by many factors. However, a large
proportion of irrigation water would be available for less than $50 a megalitre.
In contrast, one megalitre of good quality drinking water would cost an urban
household in Australia between $500 and $1,000 piped to their home.
According to Australian Bureau of Statistics (ABS) figures for 2000-01
published in May 2004, the total gross value of irrigated agricultural production
was $9,618 million.
Irrigated crops accounted for 28 per cent of the value of total agricultural
production in 2000-01.
Vegetables and fruit are the most valuable irrigated crops per megalitre of water
used while rice produces the lowest value. Rice is also the thirstiest crop per
hectare of irrigated area.
Further information about irrigation in Australia can be obtained from several
sources, including CSIRO Land and Water (http://www.clw.csiro.au), the
National Program for Irrigation Research and Development
(http://www.npird.gov.au) and the Irrigation Association of Australia
(http://www.irrigation.org.au).
BACK
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More About Catchments
In some limited areas, catchments exist in their natural state and minimal water
treatment is needed. For example, most of the water supply for Melbourne and
Canberra comes from natural wilderness catchments set aside solely for water
harvesting.
In contrast, most of Adelaide’s water is derived from the Murray River, the
catchment for which is a vast area of Australia, home to almost two million
people, containing more than 50,000 farms and referred to as the Murray
Darling Basin. The other significant source of Adelaide’s water supply is
harvested in the catchments of the Mount Lofty Ranges.
MURRAY DARLING BASIN
ADELAIDE’S MOUNT LOFTY RANGES
Within larger catchments, water harvesting can be one of a variety of often
competing activities. Other activities such as logging, farming, mineral
extraction, recreation and tourism, as well as residential and industrial
development, may occur.
As Australia has been developed, increased urbanisation, industrialisation and
intensive farming have affected the quality of water entering streams and rivers.
The water collected by such waterways requires varying degrees of treatment
before it is suitable for drinking.
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Careful land management practices can protect water quality. For example,
maintaining intact vegetation along the sides of watercourses (referred to as the
riparian zone) can protect water quality. Riparian vegetation can provide a good
natural buffer against erosion and a build-up of sediment in watercourses.
However, if such vegetation is degraded or removed, protection against the
impacts of land use on water quality is reduced.
In 2002 the National Land and Water Resources Audit published the Australian
Catchment, River and Estuary Assessment
(http:/audit.ea.gov.au/ANRA/coasts/docs/estuary_assessment/Est_Ass_Contents
.cfm). This report is the first comprehensive assessment of catchments, rivers
and estuaries in Australia
BACK
Murray Darling Basin
The Murray Darling Basin, located in south-eastern Australia, is of particular
significance as a catchment. It contains Australia’s three longest rivers, the
Darling (2740km), the Murray (2530km) and the Murrumbidgee (1690km). It
also drains 18.2 per cent of the land area of Australia containing 42.3 per cent of
the nation’s farms. Irrigation in the Murray Darling Basin accounts for about 70
per cent of the water used in agriculture in Australia.
Detailed information on the Murray Darling Basin can be obtained from the
Murray Darling Basin Commission (www.mdbc.gov.au).
BACK
Adelaide’s Mount Lofty Ranges
The major source of Adelaide’s water is the Murray River. This water is
supplemented by water from catchments in the Mount Lofty Ranges. This
locally harvested water is stored in various water supply reservoirs around
Adelaide.
The proximity of these catchments to Adelaide has meant that grazing, broad
scale cropping, intensive horticulture and urban development have occurred
there. For example, more than 70 per cent of the Onkaparinga catchment, which
supplies the Mount Bold and Happy Valley Reservoirs, is affected by urban
developments, intensive horticulture or mixed agriculture.
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Land use and water quality are closely linked. Water running from undisturbed
native vegetation is of the highest quality, while water coming from developed
areas, particularly where there is urban development and intensive horticulture,
is of lesser quality.
Because of the poor quality of the source waters, the water supply for Adelaide
requires extensive treatment before it is distributed for use.
BACK
AUSTRALIA’S LARGEST RESERVOIRS
River
Dam
Gordon (Lake Pedder)
State
Gordon
Ord River (Lake Argyle) Ord
Capacity
(megalitres)
Completed
TAS
12,450,000
1974
WA
5,797,000
1972
Eucumbene
Eucumbene
NSW
4,798,000
1958
Dartmouth
Mitta Mitta
VIC
4,000,000
1979
Eildon
Goulburn
VIC
3,390,000
1927/1955
Miena Rockfill (Great
Lake)
Shannon
TAS
3,356,000
1967
Hume
Murray
NSW
3,038,000
1936/1961
Serpentine (Lake
Pedder)
Serpentine
TAS
2,960,000
1971
Warragamba (Lake
Burragorang)
Warragamba
NSW
2,057,000
1960/1989
Burdekin Falls (Lake
Dalrymple)
Burdekin
QLD
1,860,000
1987
Source: ANCOLD Register of Large Dams in Australia
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Water recycling
A growing amount of treated effluent is used for industrial and agricultural
purposes in Australia. For example, the South Australian Water Corporation,
which provides water services in Australia’s driest state, aims to recycle 30 per
cent of the total wastewater flow from Adelaide’s wastewater treatment plants,
to reuse schemes by 2006.
Generally speaking, few additional sources of surface and/or groundwater
remain unexploited to meet the future needs of major urban communities in
Australia. These communities are demanding that the environment be managed
in a sustainable manner. This will require more water resources being allocated
to the environment rather than less. The water supply industry can no longer
rely on building new dams to quench the thirst of growing cities. It needs to
consider other strategies to match supply with demand.
In these circumstances, governments and industry have started to regard treated
urban wastewater (sewage) flows as a potential resource rather than an effluent
to be quickly discharged back into the environment at the nearest convenient
point. Urban stormwater flows are also being examined for their potential as a
water source.
While it is technically feasible to treat these sources to drinking water quality,
as currently happens with most raw water supplies, there are greater public
health risks, requiring multiple precautions and incurring greater costs.
Furthermore, the human psychological resistance to consuming our “own” has
been a major public disincentive for further considering these schemes, despite
the fact that all water is eventually recycled.
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Indirect use of wastewater for drinking has been occurring for a long time,
particularly in denser populated areas, such as Europe and the United States,
where flows from upstream cities and towns are fully treated before being
discharged to cities and towns downstream. Recycling of river water in this way
occurs less frequently in Australia, due to our smaller and less dense population.
The most frequently quoted example of direct potable reuse is by Windhoek
City Council in Namibia (Southern Africa). This water reclamation plant has
been in successful operation at Windhoek for the last 25 years for the
production of potable water for direct re-use. More recently, Singapore has
initiated the NEWater scheme, where highly purified recycled water is used to
supplement the drinking water supply
In a recent development in South Australia, below ground storage of treated
effluent is being investigated where aquifers are being recharged. The water is
intended for irrigation. For further information see:
http://www.groundwater.com.au
In recognition of the need for national guidance on water reuse for a range of
different purposes, in 2004 the Environment Protection and Heritage Council
and the Natural Resource Management Ministerial Council initiated the
development of National Guidelines for Water Recycling
(http:/www.ephc.gov.au/ephc/water_recycling.html) The guidelines will
comprise a risk management framework and specific guidance on managing the
health risks and the environmental risks associated with the use of recycled
water. The first stage of guideline development will be completed in 2006.
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Australian Drinking Water Guidelines
DEVELOPMENT OF DRINKING WATER GUIDELINES IN AUSTRALIA
Australian drinking water guidelines, first issued in 1972, tended to follow
World Health Organization recommendations, but modified for Australian
conditions. In 1987, the publication Guidelines for Drinking Water Quality in
Australia was released. Then in 1996, Australian Drinking Water Guidelines
was published jointly by the National Health and Medical Research Council
(NHMRC) and the Agriculture and Resource Management Council of Australia
and New Zealand (ARMCANZ). The Guidelines were reviewed and updated
again in 2004 and published by the National Health and Medical Research
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Council in collaboration with the Natural Resource Management Ministerial
Council (formerly ARMCANZ).
These guidelines are subject to review and are updated as new medical and
scientific information becomes available. The review is a transparent process
and submissions are routinely invited from the public, interested organisations,
state and federal governments, and scientific and professional bodies. Scientists
associated with the Cooperative Research Centre for Water Quality and
Treatment are contributing to this review process.
The document provides guidance to the Australian water industry on the
treatment levels and procedures needed to manage water supply systems that are
required to produce safe and pleasant drinking water.
An Internet version of the Australian Drinking Water Guidelines can be found
at
http://www.nhmrc.gov.au/publications/synopses/eh19syn.htm
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More on pathogens
BACTERIA
Bacteria are tiny, single-celled microorganisms that are often observed forming
colonies. They can occur in various shapes, for example, round, rod-like, or
spirals. Typically, they can be as small as half to one micron wide, and as large
as several microns long.
Bacteria capable of causing human illness through contaminated water supplies
include Campylobacter, Salmonella, Shigella, Vibrio and Yersinia.
Other bacteria of environmental origin may be found in water supplies
including Aeromonas, Legionella, Mycobacterium and Pseudomonas
aeruginosa. If found in drinking water, these bacteria are generally less of a
health risk than those of faecal origin.
VIRUSES
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Viruses are a large group of infectious agents, much smaller than bacteria, and
are able to be viewed only through an electron microscope. They are not cells
but biologically active particles that vary in size from 0.01 to 0.1 microns.
Viruses may survive in the environment for some time in soil or water, but they
cannot multiply unless they infect a suitable host. The viruses that are of
concern for water supplies can only infect humans, therefore they can arise only
from human waste.
Viruses cannot be simply cultured in the laboratory in the way bacteria are
identified, and for this reason it is difficult to detect viruses.
Problem viruses identified in the Australian Drinking Water Guidelines
include adenovirus, enterovirus, hepatitis viruses, norwalk viruses and
rotaviruses.
PROTOZOA
The term protozoa refers to a collection of generally colourless, single-celled
organisms with a well-defined nucleus. They are much bigger than bacteria,
ranging in length from 5 to 100 microns.
Protozoa are among the simplest of all living organisms. As a group, protozoa
are extremely diverse. Pathogenic protozoa found in water supplies include
Cryptosporidium, Giardia, Cyclospora, Naegleria, Acanthamoeba and
Entamoeba.
HELMINTHS
Other causes of waterborne disease in humans include helminths. These worms
or worm-like parasites infect the intestine and include roundworms, tapeworms
and flatworms. The worms in humans that originate from helminth eggs are
relatively easy to cure and present a problem only in developing countries
where proper nourishment is a problem.
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More on water-related diseases
Four types of water-related diseases are recognised in public health:
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Waterborne diseases are those where a person contracts the disease by drinking
water contaminated with the disease-causing organism. Most diseases of this
type are spread by the faecal-oral route (for instance, by swallowing small
amounts of faecal material in water, in food, or from hands).
Water-washed diseases are those which can be reduced by improving domestic
and personal hygiene. Such improvements in hygiene usually depend on the
increased availability of water for washing people, cooking utensils and
clothing, rather than the quality of the water.
These diseases include pathogens that are transmitted by the faecal-oral route,
as well as skin and eye diseases such as scabies, bacterial and fungal skin
infections, and trachoma. Other health problems, such as lice and ticks, are also
reduced by better hygiene.
Water-based diseases are those where the pathogen spends part of its life cycle
in a water snail or other aquatic animal. These diseases are caused by parasitic
worms, and include schistosomiasis and dracunculiasis (Guinea-worm).
Water-related insect-borne diseases are carried by blood-sucking insects that
breed in water or by insects that bite near water. Examples of these are diseases
such as malaria, yellow fever and dengue fever that may be carried by
mosquitos, and trypanosomiasis (sleeping sickness) carried by tsetse flies.
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More on indicator organisms
When drinking water treatment was first developed, it was recognised that
faecal contamination from humans and animals posed the greatest threat to
water supplies. A need was recognised to test untreated water to determine
whether such contamination had occurred, and treated water to check that
contamination had been successfully removed.
However, testing water for harmful microorganisms was not practical because
knowledge of the organisms responsible for disease was very limited and the
methods for detecting them were complex and time consuming.
Instead, public health microbiologists decided to search for microorganisms that
were always associated with faecal pollution, but did not cause illness. The
desirable properties of such microorganisms were:
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•
•
•
•
Always present in faeces of humans and animals.
Present in high numbers.
Easy to detect by simple and inexpensive methods.
Unable to multiply after they had left the body and entered the water supply.
Thus the presence of indicator microorganisms could serve as a warning that
faecal contamination had occurred, and that faecal pathogens might also be
present in the water supply. A series of indicator organisms was identified, and
these became the basis of microbiological quality monitoring around the world.
ESCHERICHIA COLI
E. coli is found in the intestines of animals, and does not originate from
environmental sources. For this reason, E. coli is a highly specific indicator of
faecal contamination in drinking water.
THERMOTOLERANT COLIFORMS
This group of bacteria includes E. coli and other intestinal bacteria that are able
to grow at 44°C. It also includes some bacteria that live in decaying vegetation
and agricultural or industrial waste. In some laboratories, a slightly different
testing method is used, and the bacteria detected are called faecal coliforms.
Faecal coliforms and thermotolerant coliforms are essentially the same.
Thermotolerant coliforms are less specific indicators of faecal contamination
than E. coli, because they may sometimes arise from non-faecal as well as
faecal sources.
TOTAL COLIFORMS
This is a larger group of bacteria which includes E.coli and faecal coliforms. It
also includes many non-faecal organisms that can grow in the environment.
Total coliforms occur in much greater numbers in water sources than faecal
coliforms or E. coli, and for this reason changes in their numbers (reduction by
disinfection) are easier to detect.
Total coliforms are not good indicators of faecal contamination, because they
may originate from many sources other than faeces. Increases in their numbers
in water distribution systems may be due to regrowth or external contamination.
Microbiologists can often tell the difference between contamination and
naturally occurring microorganisms in the pipeline. Contamination is likely to
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produce a growth of fairly uniform and limited number of species; natural
growth is likely to contain a much wider variety of organisms.
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HETEROTROPHIC PLATE COUNT (HPC)
The HPC measures a broad group of bacteria that are defined by their ability to
grow under certain laboratory conditions. These bacteria have no direct
relationship to faecal contamination or health risks but are used as a general
indicator of the microbiological content of water, and the levels of nutrients that
can support bacterial growth.
An elevated HPC can be useful as an early indicator of excessive bacterial
growth (possibly regrowth during warmer periods) in the distribution system,
particularly on pipe walls and sediments.
The HPC can also be a useful measurement to water authorities in managing
disinfection in distribution systems.
CHANGES IN THE USE OF INDICATOR BACTERIA
It has long been recognised that among indicator organisms, E. coli provides the
most specific warning of faecal contamination, however in the early 1900s there
was no simple test available to distinguish E. coli from other coliform bacteria.
The observation that E. coli formed the majority of coliform bacteria in human
faeces, and that total coliforms were readily isolated from contaminated waters,
led to the belief that the presence of total coliforms reflected the presence of E.
coli. Therefore total coliforms were adopted as the standard indicator organism.
At the time, sanitation standards were low and faecal contamination of water
supplies was common. Therefore at that time, total coliforms were a reasonable
surrogate for E. coli.
As sanitation standards improved in developed nations, faecal contamination of
water supplies became less common. The percentage of total coliforms in water
that were of faecal origin declined, and total coliforms were no longer a good
indicator of faecal contamination.
In 1948, the more specific test for thermotolerant coliforms (sometimes called
faecal coliforms) was developed, and this was soon adopted for general use in
water quality monitoring. Total coliform testing was retained because it had
already gained wide acceptance.
Over the years, the test methods used to identify coliform organisms have been
changed to make them simpler and more rapid, however this has also meant that
more non-faecal bacteria are now detected by the tests. Therefore the
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relationship between these indicator bacteria (total coliforms and thermotolerant
coliforms) and faecal pollution is not as definite as it used to be.
More recently, rapid and inexpensive methods for identification of E. coli have
been developed, and this organism has been adopted as the primary indicator
organism in a number of countries including Australia.
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Cyanobacteria
Cyanobacteria, also known as blue-green algae, are a group of microorganisms
with bacteria-like properties. Although not pathogenic themselves, that is they
cannot bring about an infectious disease, they produce toxins which are of
considerable concern to water supply and public health authorities.
Cyanobacteria are naturally occurring components of all aquatic environments.
Individual cells are microscopic but are capable of dividing and doubling every
two to three days and forming thick smelly green scum, the consistency of
paint, on water surfaces. These concentrations of cyanobacteria are often
referred to as “blooms”.
The species that most commonly affect water supplies in Australia are:
• Anabaena (reservoirs and slow-moving rivers).
• Microcystis and Cylindospermopsis (reservoirs and dams).
• Nodularia (brackish waters).
Some cyanobacteria produce toxins that can kill animals and are highly toxic to
humans. For example, microcystin LR (produced by Microcystis) has a relative
toxicity 1000 times greater than cyanide.
Some cyanobacterial toxins can damage the tissues of vital organs such as the
liver and kidneys, and even the skin. Other cyanobacterial toxins damage nerve
cells. There is also concern regarding long-term exposure to some toxins which
have been demonstrated to be carcinogens.
There is some debate as to the cause of blooms and in fact whether there is an
increase in their occurrence. There is no doubt that the presence of nutrients
(such as phosphate and nitrate), strong sunlight and slow flowing warm water
are conditions which favour bloom formation.
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In Australia, water authorities monitor their water sources for cyanobacteria
during warmer, sunny periods – conditions that favour growth of cyanobacteria.
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