What we're doing
Water purification and the processes proposed
Technology used
As part of its investigations into water purification, ACTEW 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. ACTEW 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.