The principal water reuse categories are summarized in Table 2. The reuse categories in Table 2 are also ranked in relative order of total usage, as practiced in the United States. Agricultural and landscape irrigation has expanded from earlier restricted uses to unrestricted irrigation of food crops eaten raw, when wastewater has been treated properly. With improved effluent water quality, there has been a global trend to diversify water reuse practices beyond agricultural and landscape irrigation, to recreational and environmental use, industrial reuse, groundwater recharge and potable reuse IPR and DPR, respectively Zhang et al.
Potable reuse is considered in the following section. Table 2. Water reuse categories, typical applications, and major constrains and concerns.
It should be noted that in these fatwas, sewage may be used for irrigation resulted that the impurities present in the raw wastewater are removed. In this project, farmers have been engaged in the beneficial use of treated wastewater in agriculture. Such projects have been successful because they have addressed not only technical and economic, but also institutional and cultural issues US AID, The RIAL projects led to the development of the first Water User Association in Jordan for the operation, maintenance, and management of treated wastewater-based irrigation systems and the introduction of the use urban wastewater effluent for the first time in this country.
Historically, wastewater, derived from wastewater collection systems, has been the principal source reclaimed water. However, population growth and urbanization combined with limited reliable water resources have also contributed to the consideration of a wider range of potential water sources for reclamation and reuse. Other potential sources of wastewater for reclamation and reuse are identified in Table 3.
Many of the potential water sources, identified in Table 3 , are most suitable for decentralized wastewater management systems see subsequent discussion. For example, in the late 's, a complete onsite wastewater recycling system was developed to produce drinking water. A number of these systems were installed at individual homes in Colorado USA , during the period from through Tchobanoglous et al.
Typically, untreated wastewater is either discharged to rivers or streams where it is diluted and transported downstream or infiltrated into aquifers, where the constituents in raw wastewater can impact freshwater supplies UNESCO, The downstream use of a water source, for drinking water, that is subject to upstream wastewater discharges is referred to as unplanned potable reuse also known as de facto potable reuse.
In some cases, reclaimed water represents a significant portion of the total flow in many receiving waters. As the world's population continues to grow, and greater stress is placed on water supplies, understanding the extent and implications of unplanned de facto PR on the design of water treatment plants will be important in protecting public health.
In addition to discharges to rivers, numerous cases have been documented where untreated wastewater applied to land for agricultural use has resulted in unplanned recharge of groundwater aquifers, from which water is withdrawn for human consumption.
Locations where such unplanned groundwater recharge has occurred include Egypt, Mexico, Peru, and Thailand. In Mexico, a large flow of wastewater from Mexico City is discharged to the arid Tula Valley also known as the Mezquital Valley where a total of , inhabitants are supplied water this way Jimenez and Asano, Recently, a study has been completed in which the degree of unplanned agricultural water reuse in selected EU river basins in Spain, Italy, and France has been documented.
This study is considered a first quantitative attempt to estimate the degree of de facto reuse in European river basins, showing a wide range of impacts from discharged wastewater among the river basins; also, varying with season Drewes et al.
While there is no reliable epidemiological evidence that the use of reclaimed water for any of its applications see Table 1 has caused a disease outbreak in the USA, potential transmission of infectious disease by pathogenic organisms is the principal concern in water reclamation and reuse. This concern is true particularly in developing countries where untreated or inadequately treated wastewater is used widely Angelakis and Rose, In addition, the production, distribution, and use of reclaimed water that is regulated inadequately may result in adverse environmental impacts.
Health and environmental issues associated with water reclamation and reuse are related to wastewater treatment, reclaimed water quality, chemical and microbiological constituents that may be present in the reclaimed water, health risk assessment, and public perception and acceptance. Reclaimed water derived from municipal wastewater comes from a variety of sources including households, schools, offices, hospitals, and commercial and industrial facilities.
Thus, untreated municipal wastewater typically contains a variety of biological and chemical constituents that may be hazardous to human health and the environment. In many developing countries, the irrigation of vegetable crops with untreated or inadequately treated wastewater is a major source of enteric diseases and other waterborne diseases.
The situation is different, however, in the United States and other industrialized countries where reliable wastewater treatment and health-related water reclamation and reuse criteria and regulations dictate the feasibility and acceptability of water reuse. Historically, as noted previously, water reuse evolved from observation, necessity, and opportunity. These factors remain the same for the contemporary period present. Although agricultural irrigation with low quality wastewater was practiced in some areas of Europe as well as the United States in the late s, there were no significant criteria or restrictions on the practice until the early part of the twentieth century.
As urban areas began to encroach on sewage farms and as the scientific basis of disease became understood more widely, concern about the health risks associated with irrigation using wastewater grew among public health officials. Subsequently, regulations have been developed for a variety of water reuse applications. The timeline of water reuse criteria and regulations is shown in Table 4. The research priorities should be directed toward the development of new criteria and regulations that will enhance the beneficial reuse of all types wastewater.
Table 4. Timeline of water reuse criteria, regulations, and standards worldwide a. It is estimated that by the world population will increase by an additional 2 billion people e.
This population growth—coupled with industrialization and urbanization—will result in an increasing demand for water and will have serious consequences on the environment. Wastewater treatment and reuse will play a vital role in future urban planning. Although there will be many different approaches to dealing with future population growth, three major trends with respect to water reuse stand out: a potable reuse PR , b integrated wastewater management IWM , and c integrated water and wastewater management.
Perhaps the most important future trend in the field of water reuse, especially in large metropolitan areas, is PR. As the name implies, PR involves the reuse of wastewater for human consumption following various treatment interventions. Today, wastewater is no longer viewed as a waste requiring disposal, but as a renewable recoverable source of drinking water, resources, and energy Tchobanoglous, The purpose here is to introduce PR and to highlight some of the issued involved.
Because the body of literature related to PR has increased dramatically, the following reports, all available on the internet, are recommended Tchobanoglous et al. When discussing PR, one of the problems is terminology.
Water reuse definitions and terminology in common use in the literature and newly adopted terminology in California are reported in Table 5. While the meanings are essentially the same, the abbreviations are not. Hopefully, this situation will be corrected in the future.
The two different types of PR are illustrated in Figure 5. Figure 5. In DPR see Figure 5B , advanced treated water is used to augment a raw water supply by blending with other water before the combined stream is treated in a drinking water treatment plant.
If the advanced water treatment facility is also permitted as a drinking water plant, finished water could potentially be introduced directly into the potable water distribution system.
In DPR, the optional engineered storage buffer ESB may be used to: a provide a water storage containment facility of sufficient volumetric capacity to retain ATW for a specified period of time until process or system corrections can be made, if there is a plant failure; b prevent blending of ATW that does not meet water quality standards with other sources of raw water; and c to prevent the addition of finished ATW that does not meet water quality standards to the drinking water distribution system Tchobanoglous et al.
Representative examples of each type of potable reuse are described in Table 6. Table 6. Representative examples of successful potable reuse projects a. The principal concerns with PR are related to public health. More specifically, acute toxicity related to pathogenic microorganisms i. Extensive research has been conducted on the methods and technologies that can be implemented to protect public health. Based on the available technologies and operating strategies, public health protection can be assured.
It is certain that new and improved treatment technologies will continue to be developed. The biggest challenge will be to assess whether constituents identified at extremely low concentration, using new and improved analytical techniques, are of any health concern. In most wastewater collection and treatment systems, wastewater is transported through the collection sewers to a centralized WWTP at the downstream end of the collection system near to the point of dispersal to the environment.
Because centralized WWTPs are generally arranged to route wastewater to these remote locations for treatment, water reuse in urban areas is often limited by the lack of dual distribution systems Tchobanoglous et al.
The infrastructure cost for storing and transporting treated water to the point s of use are often prohibitive, rendering reuse uneconomic. Thus, in the future urbanized world, greater use will be made of decentralized wastewater management systems which can be implemented at or near the point s of waste generation and reuse. A pictorial view of an IWM system is illustrated in Figure 6. Along with decentralized treatment and PR, sewer mining removal of wastewater to a large collection system for local treatment and reuse with solids processed at a central or regional WWTP as shown on Figure 6 is also an integral feature of IWM.
Figure 6. Schematic view of an integrated wastewater management system adapted from Gikas and Tchobanoglous, Another trend in the environmental engineering and water resources field is the use of the term one water to describe all forms of water.
The implications of the one water concept for municipalities would be to merge, what are now typically, individual water and wastewater departments, into one department.
By merging the two departments it is reasoned that more thoughtful, rational and cost-effective solutions can be developed to meet future water needs. In the next decade, a number of issues and challenges will need to be resolved to optimize water reclamation and reuse.
Important issues include a how to couple advanced wastewater treatment facilities with seawater desalination facilities, b the development of more effective techniques and methods incorporating risk assessment to assess human and environmental health effects of wastewater constituents, and c the development of appropriate water reclamation and reuse regulations, applicable to many different situations, that both help to promote reuse as well as regulate it.
Further, based on recent studies it was found that users of recycled water are mainly interested in the quality rather than in the origin of water Paranychianakis et al. In megacities, located on or near coastal areas, the opportunity to couple advanced wastewater treatment facilities with seawater desalination facilities will offer additional opportunities for PR.
Operationally, the effluent from the advanced treatment facility would be combined with desalinated water and treated in a membrane type water treatment plant permitted as a drinking water plant. Because both water sources are of high quality, the combined flow would be easy to treat.
The advantage this scheme offers is that drinking water could be used locally, thus avoiding the need for environmental buffers e. Another approach that has been used is to integrate seawater desalination and advanced wastewater treatment facilities to produce high quality water for industrial uses.
Typically, brine from the advanced wastewater treatment facility is blended with seawater and desalinated. Use of water produced in this integrated approach increases the amount of water available for potable and other uses. In Japan, as well as Singapore, high quality water from advanced wastewater treatment facilities is used in industrial applications.
An integrated approach is needed that combines risk assessment and risk management of water related diseases as well as health effects of chemicals and unknowns. The WHO provided a framework for the development of health-based criteria for water- and sanitation related microbial hazards as well as illness resulting from water related exposure to toxic chemicals Fewtrell and Bartram, This approach facilitates the management of disease in an integrated, holistic fashion and not in isolation from other disease or exposure routes.
Disease outcomes from different exposure routes can be compared by using a common metric, such as disability adjusted life years DALYs. Australia was the first country to develop national water quality guidelines specifically for drinking water augmentation. Recently, the guidelines have been followed-up with the development of detailed protocols for the validation of treatment performance for a number of key advanced water treatment processes Khan and Anderson, However, worldwide, the application of the risk assessment approach remains limited.
Although a large variety of water reuse criteria exists there is little standardization throughout the world. At the same time, efforts should be made to align legislation produced to protect the environment in a way which allows effective water reuse.
For the sake of integrated water management and to gain public understanding and acceptance, water reuse criteria should be part of a set of consistent water regulations applying to all forms of water reuse. What is needed is the development of comprehensive, flexible, and efficient regulatory framework based on a realistic risk assessment. In some cases e. The possibility of establishing criteria by water use category independently of the water source or origin e.
In this context, it is also important to keep in mind difference between developing and developed countries. Initially, a step by step approach is advisable in which improving current risk situation is better than having over restricted not enforceable legislations.
Starting from the historical tradition of land disposal and irrigation, water reuse has evolved into a myriad of applications, with PR representing one of the last frontiers. As in historical times, the modern practice of water reuse has evolved through observation, necessity, and opportunity. Any of these options are capable of producing water quality that has been verified through monitoring to be safe for augmenting drinking water supplies. Greywater is the term used to describe water segregated from a domestic wastewater collection system and reused on site.
This water can come from a variety of sources such as showers, bathtubs, washing machines, and bathroom sinks. It contains some soap and detergent, but is clean enough for nonpotable uses. Water from toilets or wash water from diapers is not considered to be greywater.
Kitchen sink water is not considered greywater in many states. Many buildings or individual dwellings have systems that capture, treat and distribute greywater for irrigation or other nonpotable uses. Raw Water is surface or groundwater that has not gone through an approved water treatment process.
Recycled Water is water used more than once and has been treated to a level that allows for its reuse for a beneficial purpose. Sewage is the used water of a household and commercial businesses that contains human waste. The term sewage is distinguished from industrial wastewater. The term sewage can be used interchangeably with wastewater. Wastewater is the used water of a community or industry that contains dissolved and suspended matter.
There are different types of wastewater: domestic, commercial, and industrial. Advanced Oxidation is one of the processes that can be used as a safety barrier in the water purification process.
Hydrogen peroxide, ultraviolet UV light and other processes are used in combination to form a powerful oxidant that provides further disinfection of the water and breaks down the remaining chemicals and microorganisms and provides further disinfection of the water.
Dual Media Filtration is a filtration method that uses two different types of filter media, usually sand and finely granulated anthracite. Granular Activated Carbon is a process used to remove chemicals that are dissolved in the used water. As in all processes, monitoring is important in order to check that the processes are working properly and efficiently. Membrane filtration, reverse osmosis, advanced oxidation, riverbank filtration, soil aquifer treatment, and constructed wetlands all may be parts of a multi-barrier purification process.
Not all of these processes are needed in all situations. Ozonation is the process of applying ozone O3 for the disinfection of water. Irrigation of public parks, sporting facilities, private gardens, roadsides; Street cleaning; Fire protection systems; Vehicle washing; Toilet flushing; Air conditioners; Dust control. Food crops not commercially processed; Food crops commercially processed; Pasture for milking animals; Fodder; Fiber; Seed crops; Ornamental flowers; Orchards; Hydroponic culture; Aquaculture; Greenhouses; Viticulture; Industrial uses; Processing water; Cooling water; Recirculating cooling towers; Washdown water; Washing aggregate; Making concrete; Soil compaction; Dust control.
Aquifer recharge for drinking water use; Augmentation of surface drinking water supplies; Treatment until drinking water quality. Wastewater and sewage treatment are important topics in any society, all throughout history and into today.
Improperly disposed of or treated sewage can cause disease and harm the ecosystem. That is why when a sewage overflow occurs it garners negative news attention. Skip to main content. Search Search. Water Science School. Reclaimed Wastewater. Water Use Information by Topic Learn more. Water Quality Information by Topic Learn more. For potable reuse, treatment requirements generally go beyond conventional tertiary treatment steps.
For example, the direct potable reuse plant in Namibia and the indirect potable reuse plants in Singapore NEWater and in Orange County, California Water Factory 21 all incorporate advanced drinking water treatment technologies into water reclamation schemes, such as dissolved air flotation, membrane filtration, reverse osmosis, and UV irradiation Asano et al.
It is still generally believed that nonpotable reuse can conserve water resources to the same extent as potable reuse while avoiding most of the public health risks Okun, A vast amount of information on water reclamation and reuse is available in peer-reviewed literature.
A number of notable textbooks Asano et al. Water resource managers should consult these resources for guidance on water reuse regulations and guidelines, public health risks, appropriate water reuse technologies and treatment systems, applications for reclaimed water, and appropriate steps for planning and implementing water reuse approaches. It is important to mention that most of the wastewater used in developing countries for agricultural irrigation is done so without adequate treatment Asano et al.
This often results in high burdens of enteric disease when these crops are consumed raw or undercooked. Such diseases diminish economic productivity and confine people to poverty.
However, when implemented appropriately, water reclamation and reuse can contribute to social and economic development by reducing environmental pollution and enteric disease burden and increasing household water availability and crop production. According to these guidelines, treatment options that can enable safe use of wastewater in resource-poor settings without modern centralized wastewater treatment include: waste stabilization ponds, wastewater storage reservoirs, and constructed wetlands.
WHO provides basic guidance on design factors, retention time and climatic conditions to achieve adequate pathogen reduction US EPA, Among a number of other predictions made by the Intergovernmental Panel on Climate Change, it is anticipated that climate change will lead to increased periods of drought, reduced freshwater stores, and sea level rise IPCC, However, water reclamation and reuse approaches can and have been shown to be effective for adapting water resource management in the face of such stressors.
Most importantly, water reclamation and reuse contributes to climate change adaptation by allowing water resources to be diversified and conserved.
Using reclaimed water for applications that do not require potable water can result in greatly decreased depletion of protected water sources and prolong their useful lifespan.
In addition, reclaimed water can be applied to permeable land surfaces or directly injected into the ground for the purpose of recharging groundwater aquifers and preventing saline intrusion in coastal areas. The water and nutrients that can be recovered from wastewater are simply too valuable to waste in areas where resources are limited. For this reason, it is very common for farmers in developing countries to supplement their crop irrigation supplies with wastewater.
In fact, except for a handful of cases where applications such as natural filtration systems for water reclamation Takizawa, , sewage reclamation for industrial uses Kurian and Visvanathan, , or direct potable reusei have been implemented, almost all water reclamation and reuse in developing countries is dedicated to agricultural irrigation.
Not only does this practice increase the volume of water available for crops and utilize the nutrients in wastewater in a beneficial way, it also contributes to greater quality of human life by increasing household water availability. In general, the most economically viable applications for water reuse are those that replace potable water with reclaimed water for use in irrigation, environmental restoration, cleaning, toilet flushing, and industrial uses US EPA, These applications of reclaimed water contribute directly to conservation of water resources and pollution reduction.
The financial requirements for implementing water reclamation and reuse programs will vary significantly based on the type of application that is planned for the reclaimed water. Therefore, water resource managers must fully understand the costs associated with developing and managing the particular water supply, wastewater management system, and proposed water reuse system in order to compare the costs and benefits of implementing water reclamation and reuse programs with that of maintaining traditional water and wastewater management approaches.
An economic analysis should be conducted in order to weigh the cost of maintaining traditional approaches and of possibly needing to develop additional water sources versus the cost of retrofitting existing and constructing new infrastructure for reuse applications.
Such analyses should also consider the number of financial benefits associated with water reclamation and reuse approaches, such as reduced treatment costs and the recovery of valuable nutrients from wastewater.
A particular type of economic analysis known as life cycle cost LCC analysis has been used to evaluate conditions under which water reclamation and reuse programs would be cost effective UNEP and GEC, An example of a case when the LCC approach has been used for such an application is in Tokyo, Japan, where options for wastewater reuse were compared with a conventional freshwater and sewage treatment option in a number of office buildings Yamagata et al.
The analysis found that if the reclaimed water volume was more than m3 per day, the wastewater reuse option was more cost effective when compared to the conventional freshwater and sewage treatment option. Such analyses can be very helpful in determining the economic feasibility of water reclamation and reuse programs.
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