Reclaimed water

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Reclaimed water

Reclaimed water, sometimes called recycled water, is former wastewater (sewage) that has been treated to remove solids and certain impurities, and then allowed to recharge the aquifer rather than being discharged to surface water. This recharging is often done by using the treated wastewater for irrigation. In most locations, it is only intended to be used for nonpotable uses, such as irrigation, dust control, and fire suppression, and there is controversy about possible health and environmental effects for those uses. In some locations (not in the United States), it is given more advanced treatment and is used indirectly for drinking.

History

Storm and sanitary sewers were necessarily developed along with the growth of cities. By the 1840's the luxury of indoor plumbing, which mixes human waste with water and flushes it away, eliminated the need for cesspools. Odor was considered the big problem in waste disposal and to address it, sewage could be drained to a lagoon, or "settled" and the solids removed, to be disposed of separately. This process is now called "primary treatment" and the settled solids are called "sludge." At the end of the 19th century, since primary treatment still left odor problems, it was discovered that bad odors could be prevented by introducing oxygen into the decomposing sewage. This was the beginning of the biological aerobic and anaerobic treatments which are fundamental to waste water processes. By the 1920's, it became necessary to further control the pollution caused by the large quantities of human and industrial liquid wastes which were being piped into rivers and oceans, and modern treatment plants were being built by the 1930's. Designed to make water safe for fishing and recreation, the Clean Water Act of 1972 mandated elimination of the discharge of untreated waste from municipal and industrial sources, and the federal government provided billions of dollars in grants for building sewage treatment plants around the country. Modern treatment plants, usually using sand filtration and chlorination in addition to primary and secondary treatment, were required to meet certain standards. Current treatment improves the quality of separated wastewater solids or sludge. It is known to still contain toxic chemicals and pathogens, but is now being spread on farm fields. The separated water is given further treatment considered adequate for nonpotable use by local agencies, and discharged into bodies of water, or reused as reclaimed water. In places like Florida, where it is necessary to avoid nutrient overload of sensitive receiving water, reuse of treated or reclaimed water can be more economically feasible than meeting the higher standards for surface water disposal mandated by the Clean Water Act

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 cost of reclaimed water exceed those of standard water potable water in many 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 sometimes contains higher levels of nutrients such as nitrogen, phosphorus and oxygen which may somewhat help fertilize plants when used for irrigation.

Potential problems in use for irrigation

Recent studies support long standing concerns about possible public health effects of reclaimed water. It has been known for some time that treated waste water effluent, or reclaimed water, contains pathogens that could be transferred to people through contact, including aerosols from sprinklers. Particularly worrisome are high levels of parasites such as giardia and cryptosporidium which are not killed by chlorination. In 1997, the EPA warned,"(Viable) bacteria from reclaimed water in sprinklers can travel more than 1000 feet in the air." As far back as 1984, researchers concluded that disinfection by chlorination, an important part of wastewater treatment, initially lowers the total number of sewage related bacteria, but may substantially increase the proportions of antibiotic resistant, potentially pathogenic organisms.

More recently, Chang(2007) reported that Staphyloccus aureus bacteria (responsible for MRSA) become more virulent and drug resistant after chlorination. A large study in 2006 confirms that microbes, inactivated but not killed by treatment, can regrow in retention ponds and pipes, becoming a major source of the spread of multi drug resistant pathogens in the environment. During the processing of reclaimed water, fragments can be released from microbes when their cell walls are disrupted. These fragments are not alive and not affected by disinfectants like chlorine. This intact genetic material can transfer both virulence and drug resistance to living microorganisms in water or soil. Amy Pruden(2006) demonstrates that such genetic fragments pass through sewer water reclamation plants into rivers and into drinking water sources. Since the number and types of bacteria in a treatment plant are large, a positive environment exists for transfer of drug resistance. Independent scientists found that Santa Barbara's reclaimed water contained chlorine resistant bacteria that were also resistant to eleven of the twelve antibiotics tested.

There is also concern in the industry about organic chemicals, including endocrine disruptors in wastewater In 2005,US Dept of Agriculture reported:"Overall, the environmental and public health impacts of irrigation with reclaimed sewage effluent and the potential degradation of underlying groundwater are largely unknown",

Suitable for drinking?

In most locations, reclaimed water is not directly mixed with potable (drinking) water for several reasons:

Utilities providing reclaimed water for nonpotable uses do not treat the water to drinking water standards.
Varying amounts of pathogens, pharmaceutical chemicals (e.g., hormones from female hormonal contraception) and other trace chemicals are able to pass through the treatment and filtering process, potentially causing danger to humans. Modern technologies such as reverse osmosis may help to somewhat overcome this problem. An experiment by the University of New South Wales reportedly showed a reverse osmosis system removed ethinylestradiol and paracetamol from the wastewater, even at 1000 times the expected ppm.
Drinking water standards were developed for natural ground water, and are not appropriate for identifying contaminants in reclaimed water. In addition to pathogens, and organic and endocrine disrupting chemicals, a large number of compounds may be present in reclaimed water. They cannot all be tested for, and there is a paucity of toxicity information on many of the compounds.

Because of this, state regulatory agencies do not allow reclaimed water to be used for drinking, bathing, or filling swimming pools. 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.

Lack of Testing and Standards for Irrigation Water

Reclaimed water is not regulated by the EPA but by the states, using standards formulated decades ago. Newer information shows serious public health concerns about pathogens in the water. Many pathogens cannot be detected by currently used tests. Recent literature also questions the validity of testing for "indicator organisms" instead of pathogens. Nor do present standards consider interactions of heavy metals and pharmaceuticals which may foster the development of drug resistant pathogens in waters derived from sewage.

Indirect Potable Use

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.

Unplanned Indirect Potable Use 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^-, SO4^2-, K⁺ and Na⁺, which are not removed by conventional sewage treatment.

Possible Improvements in treatment

As world populations require both more clean water and better ways to dispose of wastewater, the demand for water reclamation will increase. Future success in water reuse will depend on whether this can be done without adverse effects on human health and the environment.

In the United States, reclaimed waste water is generally treated to secondary level when used for irrigation, but there are questions about the adequacy of that treatment. Some leading scientists in the main water society, AWWA, have long believed that secondary treatment is insufficient to protect people against pathogens, and recommend adding at least membrane filtration, reverse osmosis, ozonation, or other advanced treatments for irrigation water.

Seepage of nitrogen and phosphorus into ground and surface water is also becoming a serious problem, and will probably lead to at least tertiary treatment of reclaimed to remove nutrients in future. Even using secondary treatment, water quality can be improved. Testing for pathogens using Polymer Chain Reaction (PCR) instead of older culturing techniques, and changing the discredited fecal coloform "indicator organism" standard would be improvements. In a large study treatment plants showed that they could significantly reduce the numbers of parasites in effluent, just by making adjustments to the currently used process. But, even using the best of current technology,risk of spreading drug resistance in the environment through wastewater effluent, would remain. Some scientists have suggested that there need to be basic changes in treatment, such as using bacteria to degrade waste based on nitrogen(urine) and not just carbonaceous (fecal) waste, saying that this would greatly enhance effectiveness of treatment. Currently designed plants do not deal well with things in solution, ie: pharmaceuticals. "Dewatering" solids is a major problem. Some wastes could be disposed of without mixing them with water to begin with. In an interesting innovation, solids (sludge) could be removed before entering digesters and burned into a gas that could be used to run engines. Emerging disinfection technologies include ultrasound, pulse arc electrohydrolic discharge, and bank filtration. Another issue is concern about weakened mandates for pretreatment of industrial wastes before they are made part of the municipal waste stream. Some also believe that hospitals should treat their own wastes. The safety of drinking reclaimed water which has been given advanced treatment and blended with other waters, remains controversial.

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.

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.

Worldwide acceptance

The leaders in use of reclaimed water in the U.S. are Florida and California, 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.

According to a EU-funded study "Europe and the Mediterranean countries are lagging behind" California, Japan or Australia "in the extent to which reuse is being taken up." According to the study "the concept (of reuse) is difficult for the regulators and wider public to understand and accept."

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. Some systems now exist which directly use greywater from a sink to flush a toilet or even combine the two into one piece of furniture.

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

Singapore (where it is branded as NEWater)
Payson, AZ
The Torreele project in the Veurne coastal region of Belgium, which began operating in 2002

Non-potable use

Austin, TX http://www.ci.austin.tx.us/wri/

Sydney, Australia
Tucson, Arizona
Clark County, Nevada
Clearwater, Florida
St. Petersburg, Florida
San Diego, California (San Diego County)
Contra Costa County, California
Caboolture and Maroochy (South East Queensland, Australia) LGA's currently provide Reclaimed water for industrial use (primarily capital works). Users must apply for a key to be able to access the compounds in which the outlets are located.

Proposed

In some places, reclaimed water has been proposed for either potable or non-potable use:

South East Queensland, Australia (planned for potable use as of late 2008)
Newcastle, New South Wales, Australia (proposed for non-potable use).
Canberra, Australian Capital Territory, Australia (proposed in January 2007 as a backup source of potable water)

Enterprises

Brac Systems - Canada

Maximum Water Recovery

There are various techniques that have been developed by researchers for maximum water reuse/reclamation/recovery strategies such as water pinch analysis. The techniques helps a user to target the minimum freshwater consumption and wastewater target. It also helps in designing the network that achieves the target. This provides a benchmark to be used by users in improving their water systems.