Water Purification Plant Design
In October 2007, the ACT Government announced a range of new water supply projects for the ACT region, including the design of a Demonstration Water Purification Plant. Icon Water completed the design, but construction is deferred subject to the successful implementation of the other three water security projects (Enlarged Cotter Dam, Murrumbidgee to Googong Water Transfer and Tantangara Transfer). Icon Water will continue to monitor water storage levels, rainfall and inflows to determine whether water purification is required to help secure our future water supply.
Having the design for a plant ready means that the ACT is prepared in case we need to look to water purification in future.
What is water purification?
Water purification involves processing wastewater through a multibarrier treatment system to produce high-quality drinking water. The advanced technologies used in this process include micro/ultrafiltration, reverse osmosis and advanced oxidation/ultra-violet disinfection. The purified water produced can then be added to a natural supply source, such as a water supply reservoir, to supplement drinking water supplies. It is then further treated through the drinking water treatment plant before distribution to the city.
Why did Icon Water design a 'demonstration' plant?
The purpose of a demonstration water purification plant would be to prove the reliability of the water purification process under real operational scenarios and develop a comprehensive water quality monitoring program.
The plant could also comprise a visitor education centre, where the community would learn how the water purification process produces water of drinking quality. The demonstration water purification plant would have the capacity to produce up to eight megalitres of purified water a day. This water would NOT be added to our drinking water supply. However, the plant's design would be flexible so that it could be made larger if a full Water Purification Scheme for drinking purposes became necessary for the ACT region's water security in the future.
Health and safety of water purification
Icon Water has undertaken the initial design phase of a water purification plant for demonstration purposes only. If constructed in future, the water from the demonstration water purification plant would not be added to our drinking water supply. The purpose of the plant would be to test the purification processes under real operational conditions. The plant would also demonstrate how the process produces water of drinking quality.
Like all of Canberra's drinking water, the water produced by the demonstration water purification plant would be constantly monitored to ensure it complies with strict standards. The monitoring program will confirm that the water meets or exceeds the Australian Drinking Water Guidelines.
Icon Water would also monitor the purified water to ensure that it complies with a special set of criteria called the Australian Guidelines for Water Recycling: Augmentation of Drinking Water Supplies. These national guidelines have been developed specifically for purified water.
In 2007 an independent expert panel on health investigated Icon Water's proposal to purify Canberra's wastewater and add it to the Cotter Reservoir. The panel made a suite of recommendations that Icon Water is addressing in the design of the demonstration water purification plant.
Purified water around the world
Purified water has been, or will be added to drinking water supplies in many major towns and cities around the world including Brisbane, Singapore and in the USA: Orange County; suburbs of Washington D.C; Northern Virginia; Clayton County; and Georgia. Although today's technology is much further advanced, the town of Windhoek in Namibia has been successfully using water purification for drinking purposes since the 1960s.
As part of its investigations into water purification, Icon Water has considered several treatment process options to provide a multibarrier approach to water purification. In 2007 an expert panel on health considered the suitability of each of the treatment process options available. Icon Water then adopted the expert panel's preferred treatment process, which includes membrane filtration, reverse osmosis and ultraviolet disinfection and advanced oxidation for the design of the Demonstration Water Purification Plant. Membrane filtration uses hollow fibre membranes with fine pores to remove particles and micro-organisms from water. The membrane surface acts like a very fine screen to retain the micro-organisms; similar to a screen door that retains insects, but the membrane is at a much smaller scale. This step removes microscopic particles, contaminants and pathogens.
Reverse osmosis is a water treatment process that uses pressure to force water through a membrane to separate it from dissolved salts. The membranes have very small pores, so small that most of the dissolved salts are also removed. The water would then be treated further using ultraviolet disinfection and advanced oxidation. Ultraviolet light is used to disinfect water and is effective at destroying micro-organisms such as giardia, cryptosporidium and other pathogens. Oxidation is used to breakdown chemical compounds.
Should the need for a full-scale Water Purification Scheme for the ACT arise in future, the purified water would be added to the Cotter Reservoir. There, the water would mix with the natural runoff in the catchment.
Before being piped to our taps, water from the Cotter Reservoir receives further treatment at the Mt Stromlo Water Treatment Plant. At this treatment plant water undergoes coagulation, flocculation, filtration and floatation, chlorination and UV disinfection to ensure that it is of the highest standard when it reaches our taps.
Consultation to date
In 2007, Icon Water carried out a community consultation program to find out whether ACT and Queanbeyan residents would support the idea of purifying wastewater for drinking purposes, this program was called Water2WATER.
The research found that most people (75%) were supportive of the idea, as long as Icon Water could provide assurances that any concerns around health and the investigation of other water supply options were addressed.
You can get a copy of the 2007 community consultation report by clicking here.