National Committee on Water EngineeringPlease note that this paper is held here for archival purposes, the most up to date papers are currently held on the Engineers Australia website.
Australian rainfall is considerably lower than that of other continents. Consequently, in Australia, there is little surplus after evaporation and transpiration. Fortunately Australia also has an exploitable supply of groundwater. This provides the main source of water supply over much of the arid interior of Australia.
A major limiting factor on growth in urban and rural Australia is the availability of water that is safe and suitable for drinking. Because most of the surface and underground water available in Australia is not safe for drinking in its "raw" or natural state, it requires treatment of various kinds in water treatment plants before it is suitable for distribution to consumers through town or city water supply systems.
The sustainable development of Australia will be governed in part by our ability to better manage existing drinkable water resources and to develop new resources in an ecologically sustainable manner. Water engineers have a key role in the development and supply of drinkable water through the environmentally sensitive investigation, design, construction and operation of water storages, treatment plants and distribution systems.
To be safe for drinking and other household purposes water must be free from organisms and substances harmful to human health.
The harmful organisms present in raw water include viruses, bacteria, minute animals and algae. These may cause illness or even death and before the introduction of modern water treatment processes were the cause of water-borne epidemics of cholera, typhoid and other diseases.
Depending upon the character of the surface catchment or underground aquifer from which the water is drawn, it may contain a variety of dissolved chemicals which can be harmful to health or can make water hard, corrosive or otherwise unsuitable for household or industrial purposes.
Water drawn from streams and rivers is likely to contain sediments, vegetable matter and other forms of organic matter which may make it dirty, discoloured and unpleasant to taste. These materials may also contain large numbers of pathogenic (disease-causing) organisms. Other substances which might be present in raw water could include heavy metals, pesticides and other toxic or carcinogenic compounds.
Modern water treatment plants are designed to remove most of these contaminants or to render them harmless.
The safety of drinking water is determined by scientifically derived criteria for maximum levels of certain micro-organisms and chemical compounds. The safety of a particular water supply can be assessed by laboratory analysis for these substances. Criteria have also been developed for levels of constituents that determine the acceptability of drinking water eg. non-health related inorganic salts or heavy metals. Health related and non-health related criteria form the basis of national and international guidelines on drinking water quality.
International guidelines for drinking water quality have been published by the World Health Organisation (WHO). The draft Australian Drinking Water Guidelines have been released for public comment by the National Health and Medical Research Council (NHMRC) and the Agricultural and Resource Management Council of Australia and New Zealand (ARMCAN2).
There are no national legislated standards for drinking water in Australia. Local objectives, standards of service or legislative standards are established by State or local authorities based on the national guidelines. Treatment of drinking water is frequently required to meet locally adopted standards of service. The quality of the water produced from treatment plants is regularly monitored and treatment plant operation is adjusted as appropriate to ensure that the treated water quality is safe and acceptable to consumers.
For the first time in Australia, a national strategy for managing the quality of the country's water resources - surface water, groundwater and coastal - is under development. The National Water Quality Management Strategy is a joint project of the Australian and New Zealand Environment and Conservation Council (ANZECC) and ARMCANZ. The NHMRC is associated with the project, having particular responsibility for areas of the strategy relating to public health.
The strategy aims to provide a comprehensive policy to achieve the sustainable use of the nation's water resources by protecting and enhancing their quality while maintaining economic and social development. A series of Discussion Papers, Reference Documents and Draft Guidelines have already been released for public comment. The Australian Water Quality Guidelines for Fresh and Marine Waters published under the strategy encompass ecosystem protection, water for recreation and aesthetic uses, raw water for drinking water supplies, agricultural and industrial water supplies,
The kinds of water treatment used for domestic water supply systems depend upon the nature and levels of pollutants present in the raw water. The first stage in the process of ensuring a safe supply is to choose a source of raw water that is as free from contaminants as possible. Many large metropolitan water authorities have been able to set aside catchment areas on which land use can be managed and public access controlled to maintain the quality of raw water. Where large reservoirs are used to regulate the water supply and provide an assured supply through drought periods, storage of water in the reservoir assists by removing suspended material and through the die-off of harmful organisms.
Where water is pumped from rivers or groundwater aquifers, careful siting of the pump inlets in relation to potential sources of pollution and preventing the encroachment of such sources assists in ensuring the safety of the supply.
The most common water treatment process is disinfection, which is used to kill micro-organisms harmful to human health. In Australia, disinfection usually involves the controlled injection of chlorine into the water. Residual amounts of dissolved chlorine are left in the treated water to ensure disinfection of the pipelines in the distribution system. Other disinfection agents, such as ozone, are used extensively overseas.
Floating and suspended materials such as leaves, algal matter or large soil particles are removed by screening. Finer material of colloidal size such as clay, silt, fine organic matter, algae and pathogenic organisms are removed by processes of coagulation and flocculation, which cause minute particles to floe together and settle to the bottom of sedimentation tanks, from which they can be removed by mechanical scraping. These processes are usually followed by filtration. The most common form is rapid sand filtration in which the water is forced through a graded bed of sand and gravel. The filter beds are periodically cleaned by backwashing.
The combined processes of screening, coagulation and sedimentation and filtration can remove almost all of the impurities in the water, including most of the harmful micro-organisms. Treatment with activated carbon is sometimes used in addition, particularly where there are problems of taste and odour. These processes are normally followed by disinfection which kills any surviving organisms.
In Australia, a conventional water treatment plant providing what is known as ''full treatment" will embody all the processes listed above. In some circumstances other forms of treatment will also be necessary. These may include mechanical aeration or chemical oxidation to remove unpleasant tastes or odours; chemical precipitation processes to remove hardness, iron or other heavy metals; or, particularly in remote locations dependent on groundwater with very high dissolved solids concentrations, specialised processes using ion exchange resins, reverse osmosis, membrane filtration, or electrodialysis.
After treatment to remove impurities the water is tested to ensure that it meets the required levels of water quality.
Water engineers have a key role in providing an assured water supply to towns and cities and ensuring the safety and drinkability (potability) of supply. Engineers are responsible for the identification and assessment of raw water sources; for the design, construction, operation and management of water supply reservoirs, pipelines and pumping installations, water treatment plants and water supply distribution systems.
The Institution of Engineers, Australia plays an important role in this activity by:
For further information please contact
National Committee on Water Engineering,
The Institution of Engineers, Australia
11 National Circuit Telephone. (02) 6270 6555
BARTON ACT 2600 Facsimile: (02) 6273 1488
Prepared on behalf of the National Committee on Water Engineering
Nov 1996
Australian and New Zealand Environment and Conservation Council (1992) Australian Water Quality Guidelines for Fresh and Manne Waters, National Water Quality Management Secretariat, November, Melbourne.
Australian and New Zealand Environment and Conservation Council and Australian Water Resources Council (1992) Water Quality - A National Approach, National Water Quality Management Secretariat, August, Melbourne.
Barnes D., Bliss P. J, Gould B, W, and Vallentine H. R. (1981) Water and Wastewater Engineering Systems. Longman Scientific and Technical.
Garman D. E. J., Woods L. E. and Wade A. (1983) Water Quality Issues: Water 2000. Consultants Report No 7, Australian Government Publishing Service.
National Health and Medical Research Council - Australian Water Resources Council (1987) Guidelines for Drinking Water Quality In Australia. AGPS.
National Health and Medical Research Council and Agricultural and Resource Management Council of Australia and New Zealand (1994) Draft Australian Drinking Water Guidelines, National Water Quality Management Secretariat, June, Melbourne,
Tchobanoglous G, and Schroder E. D. (1985) Water Quality. Addison-Wesley Publishing Co.
World Health Organisation (1983) Guidelines for Drinking Water Qualjty. WHO.
World Health Organisation (1994) Guidelines for Drinking Water Quality. 2nd Edition, Vol 1, WHO.
Last Modified:
Thursday, October 7, 2010 20:45
Comments to: peter.brady@eng.uts.edu.au