Water Recycling Frequently Asked Questions
| Related Links | |
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| Kwinana Water Reclamation Plant | |
| Reverse Osmosis | |
| Aquifer Replenishment on the Swan Coastal Plain - FAQ's | |
How safe is recycled water?
Where can we use recycled water?
Why use recycled water?
Where is it used now?
What is recycled water?
Wastewater is the spent or used water from a community. It comes from domestic, commercial and industrial sources and is delivered via the sewers to wastewater treatment plants. The average person produces 200 litres of wastewater every day. Wastewater is 99.97% water because by far the greatest volume comes from showers, baths and washing machines. The rest is dissolved and suspended matter. Wastewater also comes from industrial processes.
Before being recycled wastewater is treated to stringent health regulations to meet a standard that is appropriate for its intended use. When reused for a beneficial purpose this water is known as "recycled water". Currently, in Perth most treated wastewater is returned to the marine environment via ocean outlets. A small amount is returned to the environment via infiltration/evaporation ponds.
How safe is recycled water?
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Many people are concerned about health implications if they come into contact with recycled water - if they are accidentally sprayed by reticulation or receive a cut from a sporting accident or walk on wet grass. Wherever recycled water is used, strict Health Department guidelines for water quality and management including watering times must be met.
Extensive work is carried out to ensure that recycled water schemes are designed and monitored to minimise any environmental impact. Each scheme will require the approval of the Department of the Environment.
Where can we use recycled water?
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There are a number of practical options for using recycled water in WA as listed below.
Industry
Suitable industries include manufacturing, mining, mineral processing and power generation. Generally recycled water can be used for cooling or process water.
Perth’s major industrial area is in Kwinana where the top 10 users of scheme water consume 7.3 gigalitres each year. The Kwinana Water Reclamation Plant is the first major water recycling scheme for Perth. Water is treated by reverse osmosis and used in industrial processes.
Operation began in November 2004. When full demand is reached the plant will supply 6 gigalitres of low salinity recycled water to industry.
Playing fields, parks and golf courses
Playing fields, parks and golf courses use large quantities of water - usually groundwater. Replacing this supply with recycled water cam be practical and offers significant benefits. In country WA recycled water has been used for over 40 years to irrigate playing fields, parks and golf courses. In fact there are currently over 60 schemes of this type in the State.
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Horticulture/Agriculture
Horticulture and agriculture are significant users of water. Using recycled water for irrigation is possible and could provide significant reuse of the nutrients contained in recycled water. Recycled water is currently used to irrigate horticultural and orchard crops on the Northern Adelaide Plains in South Australia, and in many other parts of the world.
Woodlots
Using recycled water to grow tree crops is another common practice. Recycled water is used to irrigate a tree farm north of Albany. These trees demonstrated higher growth rates than those that are rain-fed and timber harvesters reported that quality of the wood was exceptional.
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Aquifer replenishment
Aquifer replenishment is a method whereby recycled water is recharged into the groundwater aquifers for later use. Perth is well suited for this practice with sandy soils and well defined confined and superficial aquifers. The Water Corporation is researching aquifer replenishment methods at the Halls Head wastewater treatment plant in Mandurah and at CSIRO in Floreat.
Why use recycled water?
Since 1976 Perth’s rainfall has been 12-15% lower than in the preceding 75 years. This has contributed to a much more significant decline in runoff in our surface water catchments and recharge to our groundwater resources. At the same time, there has been significant population growth in Perth and the south west region. This has increased pressure on the water resources in the area.
Using recycled water can help reduce this pressure. In some cases recycled water offers more than just environmental benefits. For example, treated wastewater contains nutrients that can be recycled by plants, reducing fertiliser costs and making it perfect for irrigation.
Where is it used now?
Reuse in Western Australia has increased significantly in recent years, due mainly to the construction of the Kwinana Water Reclamation Plant (KWRP). This supplies 17 million litres per day of highly treated recycled water to industries in the Kwinana Industrial Strip. This was a major step forward for water recycling for the Perth Metropolitan area. The KWRP plant is approaching capacity and when this occurs recycling for Western Australia will be at about 14%. Investigations are underway to expand the capacity of the KWRP plant.
There is a high level of water recycling in country areas of Western Australia, mostly for irrigation of fields, parks, school grounds and golf courses. In most cases the recycled wastewater is used directly from the treatment plant following disinfection. In Geraldton and Mandurah it is used indirectly via infiltration to the groundwater. Other uses in regional areas include irrigation of a vineyard in Mt Barker, woodlot irrigation at many south-west towns including Albany, Kemerton, Margaret River and Dunsborough and industrial uses in Pinjarra.