|
Reclaimed water, sometimes called recycled water, is former wastewater (sewage) that has been treated and purified for reuse, rather than discharged into a body of water. In some locations, it is treated to be cleaner than standard drinking water,[1] and is used indirectly for drinking. In other locations, it is only intended to be used for nonpotable uses, such as irrigating golf courses and parks, filling decorative fountains, fire fighting, and irrigating crops that will be peeled or boiled before being consumed.
History
Los Angeles County's sanitation districts have provided treated wastewater for landscape irrigation in parks and golf courses since 1929. The first reclaimed water facility in California was built at San Francisco's Golden Gate Park in 1932. In Southern California, Irvine Ranch Water District and Orange County Water District are becoming the leaders in reclaimed water through their Green Acres Project.
Benefits
The costs involved with reclaimed water typically exceed those of standard potable water in most regions of the world, where a fresh water supply is plentiful. However, reclaimed water is usually sold to citizens at a cheaper rate to encourage its use.
Using reclaimed water for non-potable use saves potable water for drinking, since less potable water will be used for non-potable uses.
It also contains higher levels of nitrogen, phosphorus and oxygen which help fertilize plants when used for irrigation.[citation needed]
Suitable for drinking?
In many locations, reclaimed water is not directly mixed with potable (drinking) water for several reasons:
- Humans may face psychological barriers against drinking reclaimed water, since it was formerly sewage.[1]
- Small amounts of pathogens and pharmaceutical chemicals (e.g., hormones from female hormonal contraception) may be able to pass through the filtering process, potentially causing danger to humans. Modern technologies such as reverse osmosis are helping to overcome this problem. An experiment by the University of New South Wales showed a reverse osmosis system removed ethinylestradiol and paracetamol from the waste water, even at 1000 times the expected ppm.[2]
- Many utilities providing reclaimed water for nonpotable uses do not treat the water to drinking water standards. However, others treat the water to a higher standard than drinking water.[1]
Because of this, some regulatory agencies ban people from drinking, bathing in or filling swimming pools with reclaimed water. They also warn those who use reclaimed water for irrigation to place a sign on their property warning people not to drink from the irrigation system, and to not use it directly on fruits or vegetables.
Some municipalities are now investigating Planned Indirect Potable Use (IPU) of reclaimed water. For example, reclaimed water may be pumped into reservoirs where it will mix with (and be diluted by) rainwater. This mixture of rainwater and reclaimed water could then be treated again, and finally used as drinking water. This technique may also be referred to as groundwater recharging or reservoir augmentation. Singapore plans to increase the amount of reclaimed water in their reservoirs from 1% to 2.5% by 2011.[1]
Unplanned Indirect Potable Use[3] has existed even before the introduction of reclaimed water. Many cities already use water from rivers that contain effluent discharged from upstream sewage treatment plants. There are many large towns on the River Thames upstream of London (Oxford, Reading, Swindon, Bracknell) that discharge their treated sewage into the river, which is used to supply London with water downstream. This phenomenon is also observed in the United States, where the Mississippi River serves as both the destination of sewage treatment plant effluent and the source of potable water. Research conducted in the 1960s by the London Metropolitan Water Board demonstrated that the maximum extent of recycling water is about 11 times before the taste of water induces nausea in sensitive individuals. This is caused by the build up of inorganic ions such as Cl-, SO42-, K+ and Na+, which are not removed by conventional sewage treatment.
Distribution and demand
Reclaimed water is often distributed with a dual piping network that keeps reclaimed water pipes completely separate from potable water pipes. In the United States, reclaimed water is always distributed in lavender (light purple) pipes to distinguish it from potable water. [4] [5]
In many cities using reclaimed water, it is now in such demand that consumers are only allowed to use it on assigned days. Some cities that previously offered unlimited reclaimed water at a flat rate are now beginning to charge citizens by the amount they use.[citation needed]
Worldwide acceptance
The leaders in use of reclaimed water in the U.S. are Florida and California,[6] with Irvine Ranch Water District as one of the leading developers. They were the first district to approve the use reclaimed water for in-building piping and use in flushing toilets.
As Australia continues to battle the 7-10 year drought, nationwide, reclaimed effluent is becoming a popular option. Already three major and capital cities in Australia, have committed to adding reclaimed effluent to their dwindling dams, including Adelaide, Brisbane and indirectly Sydney. Brisbane has been seen as a leader in this trend, and other cities and towns will review the 'Western Corridor Recycled Water Project' once completed. Already Goulbourn, Canberra, Newcastle, and Regional Victoria, Australia are also considering building a reclaimed effluent process.
Other alternatives
In urban areas where climate change has threatened long-term water security and reduced rainfall over catchment areas, using reclaimed water for indirect potable use may be superior to other water supply augmentation methods. One other commonly-used option is seawater desalination. Recycling wastewater and desalinating seawater may have many of the same disadvantages, including high costs of water treatment, infrastructure construction, and water transportation. Although the best option varies from region to region, desalination is often superior economically, as reclaimed water usually requires a dual piping network, often with additional storage tanks, when used for nonpotable use.
A less elaborate alternative to reclaimed water is a greywater system. Greywater is wastewater that has been used in sinks, baths, showers, or washing machines, but does not contain sewage (see blackwater). In a home system, treated or untreated greywater may be used to flush toilets or for irrigation. [7] Some systems now exist which directly use greywater from a sink to flush a toilet[8] or even combine the two into one piece of furniture[9].
Perhaps the simplest option is a rainwater harvesting system. Although there are concerns about the quality of rainwater in urban areas, due to air pollution and acid rain, many systems exist now to use untreated rainwater for nonpotable uses or treated rainwater for direct potable use. There are also concerns about rainwater harvesting systems reducing the amount of run-off entering natural bodies of water.
Some locations using reclaimed water
Indirect potable use
|
|
