Reclaimed water
Water reclamation (also called wastewater reuse, water reuse or water recycling) is the process of converting
There are several technologies used to treat wastewater for reuse. A combination of these technologies can meet strict treatment standards and make sure that the processed water is hygienically safe, meaning free from
The cost of reclaimed water exceeds that of
Water recycling and reuse is of increasing importance, not only in arid regions but also in cities and contaminated environments.
Definition
The term "water reuse" is generally used interchangeably with terms such as wastewater reuse, water reclamation, and water recycling. A definition by the USEPA states: "Water reuse is the method of recycling treated wastewater for beneficial purposes, such as agricultural and landscape irrigation, industrial processes, toilet flushing, and groundwater replenishing (EPA, 2004)."[7][8] A similar description is: "Water Reuse, the use of reclaimed water from treated wastewater, has been a long-established reality in many (semi)arid countries and regions. It helps to alleviate water scarcity by supplementing limited freshwater resources."[9]
The water that is used as an input to the treatment and reuse processes can be from a variety of sources. Usually it is wastewater (domestic or municipal, industrial or agricultural wastewater) but it could also come from urban runoff.
Overview
Reclaimed water is water that is used more than one time before it passes back into the natural water cycle. Advances in municipal wastewater treatment technology allow communities to reuse water for many different purposes. The water is treated differently depending upon the source and use of the water as well as how it gets delivered.
Driving forces
The World Health Organization has recognized the following principal driving forces for municipal wastewater reuse:[10][11]
- increasing water scarcity and stress,
- increasing populations and related food security issues,
- increasing environmental pollution from improper wastewater disposal, and
- increasing recognition of the resource value of wastewater, excreta and greywater.
In some areas, one driving force is also the implementation of advanced wastewater treatment for the removal of organic micropollutants, which leads to an overall improved water quality. [4]
Water recycling and reuse is of increasing importance, not only in arid regions but also in cities and contaminated environments.[5]
Already, the groundwater
option.Achieving more
Potential benefits
Water/wastewater reuse, as an alternative water source, can provide significant economic, social and environmental benefits, which are key motivators for implementing such reuse programs. These benefits include:[15][16]
- For cities and households: Increased water availability (drinking water substitution – keep drinking water for drinking and reclaimed water for non-drinking use such as industry, cleaning, irrigation, domestic uses, and toilet flushing).
- For the environment: Reduced nutrient loads to receiving waters (i.e. rivers, canals and other surface wetlands and ponds; reduced energy consumption associated with production, treatment, and distribution of water (1.2 to 2.1 kWh/m3)[17]compared to using deep groundwater resources, water importation or desalination
- Reduced manufacturing costs of using high quality reclaimed water
- In agriculture: Irrigation with treated wastewater may contribute to improve production yields, reduce the ecological footprint and promote socioeconomic benefits.[18][19] It may also lead to reduced application of fertilizers (i.e. conservation of nutrients and reducing the need for artificial fertilizer through soil nutrition by the nutrients existing in the treated effluents).[18]
Reclaiming water for reuse applications instead of using freshwater supplies can be a water-saving measure. When used water is eventually discharged back into natural water sources, it can still have benefits to ecosystems, improving streamflow, nourishing plant life and recharging aquifers, as part of the natural water cycle.[20]
Scale
Global treated wastewater reuse is estimated at 40.7 billion m3 per year, representing approximately 11% of the total domestic and manufacturing wastewater produced.
For the Sustainable Development Goal 6 by the United Nations, Target 6.3 states "Halving the proportion of untreated wastewater and substantially increasing recycling and safe reuse globally by 2030".[21]
Types and applications
Treated wastewater can be reused in industry (for example in
Categories of use | Uses |
---|---|
Urban uses | Irrigation of public parks, sporting facilities, private gardens, roadsides ; Street cleaning; Fire protection systems; Vehicle washing; Toilet flushing; Air conditioners; Dust control.
|
Agricultural uses | Food crops not commercially processed; Food crops commercially processed; Pasture for milking animals; Fodder; Fibre; Seed crops; Ornamental flowers; Orchards; Hydroponic culture; Greenhouses; Viticulture .
|
Industrial uses | Processing water; Dust control .
|
Recreational uses | Recreational impoundments with/without public access (e.g. fishing, boating, bathing); Aesthetic impoundments without public access; Snowmaking .
|
Environmental uses | Wildlife habitat; Silviculture .
|
Potable uses | Aquifer recharge for drinking water use; Augmentation of surface drinking water supplies; Treatment until drinking water quality. |
Urban reuse
In rarer cases reclaimed water is also used to augment
Usage types are distinguished as follows:
- Unrestricted: The use of reclaimed water for non-potableapplications in municipal settings, where public access is not restricted.
- Restricted: The use of reclaimed water for non-potable applications in municipal settings, where public access is controlled or restricted by physical or institutional barriers, such as fencing, advisory signage, or temporal access restriction.[16]
Agricultural reuse
The irrigation water can be used in different ways on different crops, such as for
Risks in agricultural reuse
In developing countries, agriculture is increasingly using untreated municipal wastewater for irrigation – often in an unsafe manner. Cities provide lucrative markets for fresh produce, so they are attractive to farmers. However, because agriculture has to compete for increasingly scarce water resources with industry and municipal users, there is often no alternative for farmers but to use water polluted with urban waste directly to water their crops.
There can be significant health hazards related to using untreated wastewater in agriculture. Municipal wastewater can contain a mixture of chemical and biological pollutants. In low-income countries, there are often high levels of pathogens from excreta. In
Drawbacks or risks often mentioned include the content of potentially harmful substances such as bacteria, heavy metals, or organic pollutants (including pharmaceuticals, personal care products and pesticides). Irrigation with wastewater can have both positive and negative effects on soil and plants, depending on the composition of the wastewater and on the soil or plant characteristics.[28]
Environmental reuse
The use of reclaimed water to create, enhance, sustain, or augment water bodies including wetlands, aquatic habitats, or stream flow is called "environmental reuse".[16] For example, constructed wetlands fed by wastewater provide both wastewater treatment and habitats for flora and fauna.[citation needed]
Industrial reuse
Treated wastewater can be reused in industry (for example in
Planned potable reuse
Planned potable reuse is publicly acknowledged as an intentional project to recycle water for drinking water. There are two ways in which potable water can be delivered for reuse – "Indirect Potable Reuse" (IPR) and "Direct Potable Reuse". Both these forms of reuse are described below, and commonly involve a more formal public process and public consultation program than is the case with de facto or unacknowledged reuse.[16][29]
Some water agencies reuse highly treated effluent from municipal wastewater or resource recovery plants as a reliable, drought-proof source of drinking water. By using advanced purification processes, they produce water that meets all applicable drinking water standards. System reliability and frequent monitoring and testing are imperative to their meeting stringent controls.[3]
The water needs of a community, water sources, public health regulations, costs, and the types of water infrastructure in place— such as distribution systems, man-made reservoirs, or natural groundwater basins— determine if and how reclaimed water can be part of the drinking water supply. Some communities reuse water to replenish groundwater basins. Others put it into surface water reservoirs. In these instances the reclaimed water is blended with other water supplies and/or sits in storage for a certain amount of time before it is drawn out and gets treated again at a water treatment or distribution system. In some communities, the reused water is put directly into pipelines that go to a water treatment plant or distribution system.[citation needed]
Modern technologies such as reverse osmosis and ultraviolet disinfection are commonly used when reclaimed water will be mixed with the drinking water supply.[3]
Many people associate a feeling of
Indirect potable reuse
Indirect potable reuse (IPR) means the water is delivered to the consumer indirectly. After it is purified, the reused water blends with other supplies and/or sits a while in some sort of storage, man-made or natural, before it gets delivered to a pipeline that leads to a water treatment plant or distribution system. That storage could be a groundwater basin or a surface water reservoir.
Some municipalities are using and others are investigating IPR of reclaimed water. For example, reclaimed water may be pumped into (subsurface recharge) or percolated down to (surface recharge) groundwater aquifers, pumped out, treated again, and finally used as drinking water. This technique may also be referred to as groundwater recharging. This includes slow processes of further multiple purification steps via the layers of earth/sand (absorption) and microflora in the soil (biodegradation).
IPR or even unplanned potable use of reclaimed wastewater is used in many countries, where the latter is discharged into groundwater to hold back
IPR occurs through the augmentation of drinking water supplies with municipal wastewater treated to a level suitable for IPR followed by an environmental buffer (e.g. rivers, dams, aquifers, etc.) that precedes drinking water treatment. In this case, municipal wastewater passes through a series of treatment steps that encompasses
Direct potable reuse
Direct potable reuse (DPR) means the reused water is put directly into pipelines that go to a water treatment plant or distribution system. Direct potable reuse may occur with or without "engineered storage" such as underground or above ground tanks.[16] In other words, DPR is the introduction of reclaimed water derived from domestic wastewater after extensive treatment and monitoring to assure that strict water quality requirements are met at all times, directly into a municipal water supply system.
Reuse in space stations
Wastewater reclamation can be especially important in relation to
Aboard the International Space Station,
De facto wastewater reuse (unplanned potable reuse)
De facto, unacknowledged or unplanned potable reuse refers to situations where reuse of treated wastewater is practiced but is not officially recognized.
Unplanned Indirect Potable Use[37] has existed for a long time. Large towns on the River Thames upstream of London (Oxford, Reading, Swindon, Bracknell) discharge their treated sewage ("non-potable water") into the Thames, which supplies water to London downstream. In the United States, the Mississippi River serves as both the destination of sewage treatment plant effluent and the source of potable water.[citation needed]
Design considerations
Distribution
Non-potable reclaimed water is often distributed with a dual piping network that keeps reclaimed water pipes completely separate from potable water pipes.
Treatment processes
There are several technologies used to treat wastewater for reuse. A combination of these technologies can meet strict treatment standards and make sure that the processed water is hygienically safe, meaning free from
Some water-demanding activities do not require high grade water. In this case, wastewater can be reused with little or no treatment. One example of this scenario is in the domestic environment where toilets can be flushed using greywater from baths and showers with little or no treatment.
In the case of
Wastewater is generally treated to only secondary level treatment when used for irrigation.
A pump station distributes reclaimed water to users around a city. These may include golf courses, agricultural uses, cooling towers, or landfills.
Alternative options
Rather than treating municipal wastewater for reuse purposes, other options can achieve similar effects of freshwater savings:
- Greywater reuse systems – at a household level, treated or untreated greywater may be used for flush toilets or to water a garden.
- sustainable urban drainage systems(SUDS) in the United Kingdom.
- Seawater steam distillation.
Costs
The cost of reclaimed water exceeds that of
Reclaimed water systems usually require a dual piping network, often with additional storage tanks, which adds to the costs of the system.
Barriers to implementation
Barriers to water reclamation may include:
- Full-scale implementation and operation of water reuse schemes still face regulatory, economic, social and institutional challenges.[39]
- Low economic viability of water reuse schemes.pricing systems comparable to already subsidized conventional treatment plants.[42]
- Psychological barriers, sometimes referred to as the "yuck factor", can also be an impediment to implementation, particularly for direct potable reuse plans. These psychological factors are closely associated with disgust, specifically pathogen avoidance.[43]
Health aspects
This section needs additional citations for verification. (June 2021) |
Reclaimed water is considered safe when appropriately used. Reclaimed water planned for use in recharging aquifers or augmenting surface water receives adequate and reliable treatment before mixing with naturally occurring water and undergoing natural restoration processes. Some of this water eventually becomes part of drinking water supplies.
A study published in 2009 compared the differences in water quality between reclaimed/recycled water, surface water, and groundwater.[44] Results indicated that reclaimed water, surface water, and groundwater are more similar than dissimilar with regard to constituents. The researchers tested for 244 representative constituents typically found in water. When detected, most constituents were in the parts-per-billion and parts-per-trillion range. DEET (an insect repellant) and caffeine were found in all water types and in virtually all samples. Triclosan (in antibacterial soap and toothpaste) was found in all water types, but detected in higher levels (parts-per-trillion) in reclaimed water than in surface or groundwater. Very few hormones/steroids were detected in samples, and when detected were at very low levels. Haloacetic acids (a disinfection by-product) were found in all types of samples, even groundwater. The largest difference between reclaimed water and the other waters appears to be that reclaimed water has been disinfected and thus has disinfection byproducts (due to chlorine use).
A 2005 study found that there had been no instances of illness or disease from either microbial pathogens or chemicals, and the risks of using reclaimed water for irrigation are not measurably different from irrigation using potable water.[45]
A 2012 study conducted by the
Environmental aspects
Using reclaimed water for non-potable uses saves potable water for drinking, since less potable water will be used for non-potable uses.[47]
It sometimes contains higher levels of nutrients such as nitrogen, phosphorus and oxygen which may help fertilize garden and agricultural plants when used for irrigation.[citation needed]
Fresh water makes up less than 3% of the world's water resources, and just 1% of that is readily available. Even though fresh water is scarce, just 3% of it is extracted for human consumption. The remaining water is mostly used for agriculture, which uses roughly two-thirds of all fresh water.[48][49][50]
Reclaimed water can offer a viable and effective alternative to freshwater where freshwater supplies are scarce. Reclaimed water is utilized to maintain or increase lake levels, restore wetlands, and restore river flows during hot weather and droughts, protecting biodiversity. Additionally, reclaimed water is utilized for street cleaning, irrigation of urban green spaces, and industrial processes. Reclaimed water has the advantage of being a consistent source of water supply that is unaffected by seasonal droughts and weather changes.[49][50][51]
The usage of water reclamation decreases the pollution sent to sensitive environments. It can also enhance
The main potential risks that are associated with reclaimed wastewater reuse for irrigation purposes when the treatment is not adequate are the following:[52][53]
- antibiotic resistancedeterminants;
- Soil salinization and accumulation of various unknown constituents that might adversely affect agricultural production;
- Distribution of the indigenous soil microbial communities;
- Alteration of the and their transformation products), etc.) in it and subsequent uptake by plants and crops;
- Excessive growth of algae and vegetation in canals carrying wastewater (i.e. eutrophication);
- Groundwater quality degradation by the various reclaimed water contaminants, migrating and accumulating in the soil and aquifers.
Guidelines and regulations
International organizations
- World Health Organization (WHO): "Guidelines for the safe use of wastewater, excreta and greywater" (2006).[10]
- United Nations Environment Programme (UNEP): "Guidelines for municipal wastewater reuse in the Mediterranean region" (2005).
- United Nations Water Decade Programme on Capacity Development (UNW-DPC): Proceedings on the UNWater project "Safe use of wastewater in agriculture" (2013).
European Union
Since 26 June 2023[54] there is an EU regulation on minimum requirements for water reuse for irrigation purposes.[55] The water quality requirements are divided into four categories depending on what is irrigated and how the irrigation is performed. The water quality parameters included are E.coli, BOD5, total suspended solids (TSS), turbidity, legionella, and intestinal nematodes (helminth eggs).
In the Water Framework Directive, reuse of water is mentioned as one of the possible measures to achieve the Directive's quality goals. However, this remains a relatively vague recommendation rather than a requirement: Part B of Annex VI refers to reuse as one of the "supplementary measures which Member States within each river basin district may choose to adopt as part of the programme of measures required under Article 11(4)".[56]
Besides that, Article 12 of the Urban Wastewater Treatment Directive concerning the reuse of treated wastewater states that "treated wastewater shall be reused whenever appropriate", which some consider not specific enough to promote water reuse as it may leave too much room for interpretation as to what can be considered as an "appropriate" situation to reuse treated wastewater.
Despite the lack of common water reuse criteria at the EU level, several member states have issued their own legislative frameworks, regulations, or guidelines for different water reuse applications (e.g. Cyprus, France, Greece, Italy, and Spain).
However, an evaluation carried out by the European Commission on the water reuse standards of several member states concluded that they differed in their approach. There are important differences among the standards regarding permitted uses, parameters to be monitored, and limit values allowed. This lack of harmonization among water reuse standards could potentially create trade barriers for agricultural goods irrigated with reclaimed water. Once on the common market, the level of safety in the producing member states may be not considered sufficient by the importing countries.[57] The most representative standards on wastewater reuse from European member states are the following:[56]
- Cyprus: Law 106 (I) 2002 Water and Soil pollutioncontrol and associated regulations (KDP 772/2003, KDP 269/2005) (Issuing Institutions: Ministry of Agriculture, Natural resources and Environment, Water Development Department).
- France: Jorf num.0153, 4 July 2014. Order of 2014, related to the use of water from treated urban wastewater for irrigation of crops and green areas (Issuing Institutions: Ministry of Public Health, Ministry of Agriculture, Food and Fisheries, Ministry of Ecology, Energy and Sustainability).
- Greece: CMD No 145116. Measures, limits and procedures for reuse of treated wastewater (Issuing Institutions: Ministry of Environment, Energy and Climate Change).
- Italy: DM 185/2003. Technical measures for reuse of wastewater (Issuing Institutions: Ministry of Environment, Ministry of Agriculture, Ministry of Public Health).
- Portugal: NP 4434 2005. Reuse of reclaimed urban water for irrigation (Issuing Institutions: Portuguese Institute for Quality).
- Spain: RD 1620/2007. The legal framework for the reuse of treated wastewater (Issuing Institutions: Ministry of Environment, Ministry of Agriculture, Food and Fisheries, Ministry of Health).
By 2023, a new EU agriculture law may raise water reuse by six times, from 1.7 billion m3 to 6.6 billion m3, and cut water stress by 5%.[48][58][needs update]
United States
In the U.S., the
Denver's Direct Potable Water Reuse Demonstration Project[60] examined the technical, scientific, and public acceptance aspects of DPR from 1979 to 1993. A chronic lifetime whole-animal health effects study on the 1 MGD advanced treatment plant product was conducted in conjunction with a comprehensive assessment of the chemical and microbiological water quality. The $30 million study found that the water produced met all health standards and compared favorably with Denver's high quality drinking water. Further, the projected cost was lower than estimates for obtaining distant new water supplies.
Reclaimed water is not regulated by the U.S. Environmental Protection Agency (EPA), but the EPA has developed water reuse guidelines that were most recently updated in 2012.[61][62] The EPA Guidelines for Water Reuse represents the international standard for best practices in water reuse. The document was developed under a Cooperative Research and Development Agreement between the EPA, the U.S. Agency for International Development (USAID), and the global consultancy CDM Smith. The Guidelines provide a framework for states to develop regulations that incorporate the best practices and address local requirements.
Reuse of reclaimed water is an increasingly common response to water scarcity in many parts of the United States. Reclaimed water is being reused directly for various non-potable uses in the United States, including urban landscape irrigation of parks, school yards, highway medians and golf courses; fire protection; commercial uses such as vehicle washing; industrial reuse such as cooling water, boiler water and process water; environmental and recreational uses such as the creation or restoration of wetlands; as well as agricultural irrigation.[63] In some cases, such as in Irvine Ranch Water District in Orange County, it is also used for flushing toilets.[64]
It was estimated that in 2002 a total of 1.7 billion US gallons (6,400,000 m3) per day, or almost 3% of public water supply, were being directly reused. California reused 0.6 and Florida 0.5 billion US gallons (1,900,000 m3) per day respectively. Twenty-five states had regulations regarding the use of reclaimed water in 2002.[63] Planned direct reuse of reclaimed water was initiated in 1932 with the construction of a reclaimed water facility at San Francisco's Golden Gate Park. Reclaimed water is typically distributed with a color-coded dual piping network that keeps reclaimed water pipes completely separate from potable water pipes.[65]Trade associations
- The WateReuse Association is a trade association in the United States which promotes reuse of water. According to their website, "The WateReuse Association is the nation's only trade association solely dedicated to advancing laws, policy, funding, and public acceptance of recycled water. WateReuse represents a coalition of utilities that recycle water, businesses that support the development of recycled water projects, and consumers of recycled water."[66] The WateReuse Research Foundation was merged into the WateReuse Association on July 11, 2016.[67]
Other countries
- Canada: "Canadian guidelines for domestic reclaimed water for use in toilet and urinal flushing" (2010).
- China: China National Reclaimed Water Quality Standard; China National Standard GB/T 18920-2002, GB/T 19923-2005, GB/T 18921-2002, GB 20922-2007 and GB/T 19772-2005.
- Israel: Ministry of Health regulation (2005).
- Japan: National Institute for Land and Infrastructure Management: Report of the Microbial Water Quality Project on Treated Sewage and Reclaimed Wastewater (2008).
- Jordan: Jordanian technical base n. 893/2006 Jordan water reuse management Plan (policy).
- Mexico: Mexican Standard NOM-001-ECOL-1996 governing wastewater reuse in Agriculture.
- South Africa: The latest revision of the Water Services Act of 1997 relating to grey-water and treated effluent (Department of Water Affairs and Forestry, 2001).
- Tunisia: Standard for the use of treated wastewater in agriculture (NT 106-109 of 1989) and list of crops that can be irrigated with treated wastewater (Ministry of Agriculture, 1994).
- Australia: National level Guidelines: Government of Australia (the Natural Resource Management Ministerial Council, the Environment Protection and Heritage Council, and the Australian Health Ministers Conference (NRMMC-EPHC-AHMC)): Guidelines for water recycling: managing health and environmental risks" Phase 1, 2006.[56]
History
Wastewater reuse (planned or unplanned) is a practice which has been applied throughout human history and is closely connected to the development of sanitation.[68]
Country examples
Australia
Israel
Namibia
Singapore
Water reclaimation was pursued primarily due to geopolitical tensions arising from Singapore’s dependency on water imported from Malaysia
South Africa
In South Africa, the main driver for waste
See also
- One Water (water management)
- Water conservation
- Water heat recycling
- Water recycling shower
- WateReuse
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Further reading
- Hoffman, Steve. Planet Water: Investing in the World’s Most Valuable Resource. New York: Wiley, 2009.
- Pearce, Fred. When the Rivers Run Dry: Water-The Defining Crisis of the Twenty-First Century. Boston: Beacon Press, 2007.
- Solomon, Steven. Water: The Epic Struggle for Wealth, Power, and Civilization. New York: Harper, 2010.