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  • Published: 30 April 2020

Contributions of recycled wastewater to clean water and sanitation Sustainable Development Goals

  • Cecilia Tortajada 1  

npj Clean Water volume  3 , Article number:  22 ( 2020 ) Cite this article

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  • Social policy
  • Water resources

Water resources are essential for every development activity, not only in terms of available quantity but also in terms of quality. Population growth and urbanisation are increasing the number of users and uses of water, making water resources scarcer and more polluted. Changes in rainfall patterns threaten to worsen these effects in many areas. Water scarcity, due to physical lack or pollution, has become one of the most pressing issues globally, a matter of human, economic and environmental insecurity. Wastewater, whose value had not been appreciated until recently, is increasingly recognised as a potential ‘new’ source of clean water for potable and non-potable uses, resulting in social, environmental and economic benefits. This paper discusses the potential of recycled wastewater (also known as reused water) to become a significant source of safe water for drinking purposes and improved sanitation in support of the Sustainable Development Goals.

Introduction

The Sustainable Development Goals (SDGs) are the most recent attempt by the international community to mobilise government, private and non-governmental actors at national, regional and local levels to improve the quality of life of billions of people in the developed and developing worlds. The goals are an ambitious, challenging and much-needed action plan for “people, planet and prosperity” until the year 2030 1 .

Of the 17 SDGs, the sixth goal is to “ensure availability and sustainable management of water and sanitation for all”. The achievement of this goal, even if partially, would greatly benefit humankind, given the importance of clean water for overall socio-economic development and quality of life, including health and environmental protection.

In 2000, the Millennium Development Goals (MDGs) aimed at reducing by half the proportion of the population without sustainable access to safe drinking water and sanitation by 2015. This objective, however, did not take into consideration water quality or wastewater management aspects, which represented a main limitation for its achievement 2 . This omission has been rectified in the Sustainable Development Goals (SDGs), where one of the goals (SDG 6) calls for clean water and sanitation for all people by ensuring “availability and sustainable management of water and sanitation for all”. Among other aspects, it considers improvement of water quality by reducing by half the amount of wastewater that is not treated, and increasing recycling and safe reuse globally. This will result in the availability of more clean water for all uses, and on an enormous progress on sanitation and wastewater management. This target unequivocally indicates the close interrelation between clean water, sanitation and wastewater management, giving these two last aspects the importance they deserve. No government of any human settlement irrespective of its size, be it a megacity, mid-size city or large or small town, can provide clean water without concurrently considering sanitation and wastewater management. Clean water is not, and will never be possible, if wastewater is not collected, treated and disposed properly for the intended uses.

Constraints for the provision of clean water and sanitation for all are complex, and depend on decisions of actors at all levels of government, private sector, non-governmental organisations and the public. They are also determined by broad development policies that may or may not prioritise provision of these services over the long-term, national and local action plans that, even when properly formulated, are often not adequately implemented due to short-term planning, lack of managerial, financial and/or man-power capacity and water needs of other sectors such as the energy or agriculture sectors on which the water sector has limited say or control. The most damaging limitation is often political will that is not sustained and that depends on political interests and electoral cycles. These aspects as well as many others that hampered the progress of the MDGs and represent serious constraints for the SDGs include discrepancy between global goals and national and local limitations, lack of continuity in decisions, policies and investments from one administration to the other, poor or inexistent data that inform decision-making or disadvantaged populations that do not have access to appropriate water and sanitation services 3 .

In most developing countries, provision of clean water and, to a certain degree, also sanitation services, are prioritised over other services. Nevertheless, this prioritisation is not always accompanied by sustained support, resources, or interest. Regarding wastewater management, this is simply left behind. There does not seem to be appreciation of the numerous negative impacts wastewater and related pollution have for provision of clean water, and how much they adversely affect human health and the environment.

It is a fact that water resources globally are under pressure from economic development, population growth, urbanisation, and more recently, climate variability and change; however, it is also pollution to a large extent what is restricting the availability of water for all people for all uses in quantity and quality. It is difficult to find a solution because, as discussed earlier, this depends on numerous technical and non-technical decisions that are taken without analysing their implications on water availability. The situations are further exacerbated by legal and regulatory frameworks that are not implementable, absence of long-term planning, inadequate management and governance, government capability, neglect of demand-side practices (pricing and non-pricing measures), disregard of awareness building including attitudes and behaviour, and poor intersectoral collaboration. Adequate consideration of these aspects depends on economic, social, environmental, cultural and political contexts and institutional capabilities of the places where they are implemented. Properly pursuing SDGs in general, and SDG 6 in particular, have the potential to improve not only access to water and sanitation and quality of life of billions of people, but also contributing towards better capacities of national and local governments.

SDGs main targets of reducing by half the amount of wastewater that is not treated, and increasing recycling and safe reuse present the distinct possibility of producing ‘new’ sources of clean water for all uses that would not be available otherwise. It would further mean that wastewater discharged to water bodies would be cleaner and safer than what it is at present, and that source water for communities downstream would be of much better quality. It would further contribute to improvements in aquatic environments.

Potable water reuse is not new. However, what has made it more relevant at local and also at national levels such as in Singapore, and now potentially in United States, is growing water scarcity and pollution that is reducing water resources available for larger populations and more uses.

The rest of the paper presents the poor status of water quality globally, and discusses the distinct potential wastewater treatment and reuse have to produce new sources of clean water, as well as to improve sanitation and wastewater management, supporting the UN’s development goal of clean water and sanitation for all. This would also contribute, at least partially, to the progress of several others non-water related SDGs such as poverty alleviation, good health and well-being, and improved education and gender equality. Examples of projects that produce reused water for potable purposes are presented including their benefits, as well as the views of the local populations. Finally, challenges to implement potable water reuse more extensively are discussed.

Results and Discussion

Water pollution and impacts on human health and environment.

Worsening water pollution affects both developed and developing countries. In developing countries, it is mostly due to rapid population growth and urbanisation, increased industrial and other economic activities, and intensification and expansion of agriculture, coupled with lack of local and national legal and institutional capacities (managerial, technical, financial, enforcement, etc.) and political and public apathy to improve and maintain water and wastewater management processes in the long-term. Much attention is given to sanitation, specially to construction of toilets and wastewater treatment plants, but their construction alone will not improve water quality over medium- and long-terms unless commensurate attention is given to significantly improving institutional capacity for planning, management, and implementation 4 .

Water pollution has increased significantly in most rivers in Africa, Asia and Latin America since 1990. Pathogenic and organic pollution has worsened in more than half of river stretches, severely limiting their use. These findings are based on measurements of parameters that indicate pathogen pollution (faecal coliform bacteria), organic pollution (biochemical oxygen demand), and salinity (total dissolved solids) 5 . Although sanitation coverage and wastewater treatment have improved in some countries, they have not been enough to reduce the faecal coliform pollution reaching surface waters 6 . This does not include contamination due to industrial and agricultural wastewater which discharges contain hazardous chemicals, heavy metals, and other inorganic pollutants. Consequently, an estimated 2 billion people use drinking water sources that are contaminated, making millions sick.

According to the Global Burden of Disease studies 7 , between 1990 and 2017, the worst deterioration of water quality was in Southeast Asia, East Asia, and Oceania (86% increase in the parameters measured), North Africa and the Middle East (58% increase), and South Asia (56% increase). Parameters used to estimate unsafe water sources include proportion of individuals globally with access to different water sources (unimproved, improved except for piped supply, or piped water supply), and who have reported use of household water treatment methods such as boiling, filtering, chlorinating or solar filtering (or none of these). For unsafe sanitation, the parameters used are the proportion of individuals with access to different sanitation facilities (unimproved, improved except sewer, or sewer connection).

In developed countries, people’s access to safe sources of water and to sanitation and wastewater services has improved. However, these services still lag behind for people in poor urban, peri-urban, and rural areas, showing inequality among and within communities and regions, with the poorest people generally being in the most difficult situations 8 . Water quality has also improved in general, but pollutants have multiplied and diversified, putting pressure on governments and utilities to improve treatment processes for both drinking water and wastewater 9 .

United States, for example, acknowledges new and long-standing problems. These include a combination of point sources of pollution (such as toxic substances discharged from factories or wastewater treatment plants) and non-point sources (such as runoff from city streets and agricultural sources like farms and ranches). Another problem has been insufficient financial support for municipal wastewater treatment plants 10 . In 2009, according to data reported by the EPA (2009) 11 and the states, 44% of river and stream miles assessed, and 64% of lake acres assessed, did not meet applicable water quality standards and were not apt for one or more intended uses. In 2019, an assessment of lakes at the national level found that ~20% of them had high levels of phosphorus and nitrogen 12 . Although more work is necessary, the United States has the advantage of robust legal and institutional frameworks that have fostered progress in improving quality in drinking water and bodies of water.

Europe is not without problems. According to the European Environment Agency 13 , good chemical status has been achieved for only 38% of surface waters and 74% of groundwater in the EU member states. Surface water bodies are affected mostly by hydromorphological pressures (40%), non-point sources of pollution (38%, mostly agricultural), atmospheric deposition (38%, mainly mercury), point sources of pollution (18%) and water abstraction (7%). In England, only 14% of rivers meet the minimum good status standard; France, Germany, and Greece have been fined by the European Court of Justice for violating regulatory limits on nitrates, with almost a third of monitoring stations in Germany showing levels of nitrates exceeding EU limits.

Risks posed by emerging contaminants such as pharmaceuticals and microplastics are still poorly understood, and thus cannot be adequately incorporated in planning and management of potable water supply. Current and future research on emerging contaminants and their impacts is necessary to fully understand the best management and treatment processes.

Safe reuse for additional sources of safe water

Safe reuse of water resources (using them more than once) is a radical contribution to the old paradigm of water resources management, which seldom considered the value of recycled wastewater and its reuse for potable uses. Larger populations that require more water and produce more wastewater that is not always treated properly, current and projected water scarcity and degradation and water-related health and environmental concerns have led a growing number of cities to treat municipal wastewater to higher quality, and either reusing it for potable and non-potable purposes or discharging it (now cleaner) to the environment. Appropriate regulations, improved technology, more reliable monitoring and control systems, and considerations of public views have made it a feasible alternative to increase the amount of clean water available for potable purposes 14 .

Augmentation of water resources for potable purposes with reused water can be done either directly or indirectly. Terminology varies, but generally, in indirect potable reuse (IPR), reused water is introduced into an environmental buffer (reservoir, river, lake or aquifer) and then treated again as part of the standard supply process. In direct potable reuse (DPR), reused water is sent to a drinking water treatment plant for direct distribution without going through an environmental buffer.

Potable water reuse projects have been implemented in cities in the United States, Namibia, Australia, Belgium, United Kingdom and South Africa, as well as in Singapore 15 . The common denomination in all cases for project development has been water scarcity. All projects have prioritised public health and the environment and risk management. Because water reuse diversifies the water resources available, its value has become more evident during droughts, when surface and groundwater are more limited for all uses.

Local experiences considered successful

This section refers to potable water reuse in several cities, with emphasis on United States because of its current progress in this area.

United States has developed the largest number of water reuse projects of any country, supported by policies and regulations that promote safe reuse of water from recycled wastewater (in 2017, 14 states had policies to address indirect potable reuse and three to address direct potable reuse, compared with eight and none, respectively, in 2012). Measures have been taken to improve use and management of freshwater resources, developing water management tools and drought preparedness plans, conservation actions, addressing dependence on expensive inter-basin water transfers, assessing climate change, and revising water reuse from the knowledge, management, technological, financial, and public-opinion viewpoints.

In US, there are no specific federal regulations for potable water reuse; however, all potable water should meet federal and state water quality regulations, such as the Safe Drinking Water Act and the Clean Water Act. In parallel to these Acts, several states have developed their own regulations or guidelines governing indirect potable reuse, while direct potable reuse facilities are currently considered on a case-by-case basis. In Big Spring and Wichita Falls, Texas, direct potable reuse has been implemented as the most effective, or the only feasible way to provide clean water 16 .

California is the most progressive state regarding indirect potable water reuse, with the most developed regulatory frameworks. For more than 50 years, several cities have implemented planned replenishment of groundwater basins with reused water. Regulations were adopted in 1978 and revised in 2014. In 2018, indirect potable reuse regulations of surface water augmentation were adopted. They allow reused water to be added to surface water reservoirs that are used as sources of drinking water 17 . No project has been implemented yet but the first two (in San Diego County) are expected to be completed by 2022.

The state does not have regulations for direct potable reuse at present. However, the State Water Board is working on a Proposed Framework for Regulating Direct Potable Reuse to develop uniform water recycling criteria that will protect public health, and avoid “discontinuities” in the risk assessment/risk management approach as progressively more difficult conditions are addressed 18 .

The best-known potable reuse project in California, in the country, and internationally, is the Orange Country Groundwater Replenishment System. Indirect potable reuse has been the long-term response of the district (as has been for the state) to provide clean water for growing human and environmental needs. The system supplies potable reused water for ~850,000 people. Reused water is for recharging the groundwater basin to protect it from seawater intrusion. A final expansion project will increase the system’s treatment capacity, enabling the district to continue protecting the groundwater basin and providing clean water to its growing population 19 . The project is considered a precursor and benchmark for subsequent water reuse projects in El Paso, Texas, the West Basin Water Recycling Plant in California and the Scottsdale Water Campus in Arizona.

A recent initiative of the EPA, the National Water Reuse Action Plan, has the potential to implement water reuse at the national level. This Action Plan, announced in February 2020, has the objective to secure the country’s water future for all uses by improving security, sustainability, and resilience of water resources through water reuse and identify types of collaboration between governmental and nongovernmental organisations to make this possible. The plan also aims to address policy, programmatic issues, and science and technology gaps to better inform related regulations and policies 20 .

Reused water has also been produced in Windhoek and Singapore. Windhoek is the first example of direct potable reuse globally from 1968, as the best, and only alternative to water scarcity, exacerbated by recurrent droughts 21 . Given its importance for water security, potable reuse has been considered for decades as a strategic component of water resources management. During the very severe drought in 2015–2017, surface water (the main water source) fell to 2% of supply from the normal 75%, putting enormous pressure on the water system and on the domestic, commercial and industrial sectors. Most of the water used to replace the surface water was drawn from the local aquifer, and potable reused water increased to 30% of supply 22 . Potable water reuse additional domestic supplies and domestic water rationing was not necessary. From October 2019 and through the writing of this article in early 2020, Windhoek faced another very severe drought during which potable water reuse also represented an essential source of clean water for potable purposes, until it finally rained.

In Singapore, production of NEWater (as reused water is known) started in 2003 as part of a long-term strategy to diversify water resources and reduce Singapore’s dependence on water imported from Johor, Malaysia, with a goal of resilience and self-sufficiency by 2060. Reused water meets ~40% of Singapore’s daily water needs and will cover ~55% by 2060. During dry months, NEWater is added to the reservoirs to blend with raw water before undergoing treatment and being supplied for potable use 23 . While water reuse was not a new concept in 2003, what has been significant in this case is its large-scale implementation and the wide public acceptance of indirect potable and direct non-potable reuse due comprehensive education and communication strategies 24 . These emphasise the water-scarcity reality in the city-state and the importance of water reuse to produce the water that is needed for overall development.

In Europe, the EU recognises the importance of reducing pressures on the water environment due to water scarcity, and encourages efficient resource use. Its policy on water reuse does not include potable uses, leaving this decision to the member states; it refers only to non-potable uses, with focus on irrigation for agriculture 25 .

Within this framework, the only two projects that have been developed in the region so far are the Langford Recycling Scheme in United Kingdom and Torrelle plant in Belgium. Both produce water to be used indirectly for drinking water supplies. The Langford Recycling Scheme operates only when the flow of the River Chelmer is low, supplying up to 70% of the flow during drought periods. The highest production has been during drought periods in 2005–2006 and 2010–2011 26 . In Belgium, Torrelle plant supplies safe drinking water to nearby communities, ~60,000 people in 2012, and is also used for artificial recharge of the dune aquifer of Saint-André preventing seawater intrusion 27 .

Table 1 presents an overview of the projects mentioned above 28 . In the decades over which these projects have supplied drinking water, no negative health effects have been documented.

Local experiences where challenges remain

The most recent potable reuse projects that have been stopped are in Australia. The country has robust legal and regulatory frameworks to support potable reuse 29 , but so far only one project has been successfully implemented, in Perth, Western Australia 30 . Two potable water reuse projects in Queensland have been halted due to health concerns, poor communication and public opposition in one case (Toowoomba 31 ), and on lack of political support in the other case (Western Corridor Recycled Water Project) 32 . In both cases, decisions were taken even when there were concerns on the impacts of climate change in the region and the possibility that rainfall patterns might not be appropriate for future purposes.

Acceptance of potable water reuse requires robust regulations and advanced technology; however, it also requires serious consideration of the soft-aspects such as education, communication and engagement of politicians, decision-makers and the public, and emotional response and trust 33 . Messages should not be limited to the benefits of the projects. They should also discuss aspects such as water quality and safety, water supply alternatives and their feasibility and costs, risk management, and implications for those who will consume the water 34 .

In the developing world, cities in Brazil, Mexico, Kuwait, and India have constructed or are planning projects, for potable water reuse. Their possibilities to succeed are limited as projects would have to be implemented within regulatory, institutional, governance, management, financial and technological frameworks that are robust and promote innovation, and utilities would have to ensure technical, managerial and financial capacities in the long-term. A serious limitation is that water management in general, and collection and conventional treatment of municipal and industrial wastewater in particular, are still challenging; often water quality standards and monitoring are poorly enforced, and risk assessment frameworks are lacking. Irrespective of how important potable water reuse is for clean water and sanitation goals at local, regional and national levels, challenges remain for its extended implementation.

Knowledge gaps and research needs

Protection of human health and the environment is paramount for any source of drinking water, be it reused water or not. To ensure reused water is safe for potable purposes, it is crucial that it meets standards for pathogens and chemicals (federal, state and local), monitoring is robust, comprehensive and continuous, reporting and independent auditing are performed and knowledge gaps and research needs are addressed 35 .

Overall, types of research needed include further evaluations of common drinking water treatment processes and their inactivation and/or removal efficiency, regulated and unregulated contaminants and their expected presence in reused water, microbial, chemical, radiological and emerging contaminants, monitoring of the influents and effluents of water treatment plants and real-time monitoring of water as it passes through the treatment train. This will facilitate rapid responses, immediately identifying any changes in the water quality due to pathogens or chemical pollutants, detect their types and amounts, and decide on the most appropriate response 36 . General risks can also be reduced through wastewater source control, water source diversification and allocation of risks, so that each party can manage the different risks.

A growing area of concern is the presence of commonly used chemicals and emerging contaminants, their mixture even at low doses, and their effect in human health and ecosystems. This is particularly important if they are detected more often in advanced treated water as they can cause acute or chronic diseases. Better regulations, and improved treatment and monitoring have been identified as key to address the above issues and comply with potable water quality parameters 37 . Web-based data analytics and a system for population water reporting are also important as they will enhance data collection, and increase information accessibility.

To further understand risks of emerging contaminants, major research efforts based on toxicological and epidemiological studies have been carried out. At present, however, health and environmental protection relies in the measurement of chemical and microbiological parameters and the application of formal processes of risk assessment. The objective is that identification, quantification and use of risk information informs decision-making on social and environmental impacts and benefits, as well as on financial costs 38 . Effects on vulnerable groups like infants, elderly, pregnant women, and persons who are already ill, are less understood and thus require additional research.

In direct potable reuse, the absence of an environmental buffer means shorter failure response times, which may affect the ability of plant operators to stop operations if off-specification water is detected. In these cases, supplementary treatment, monitoring, and engineered buffers are expected to provide equivalent protection of public health and response time if water quality specifications are not met 39 .

Table 2 lists benefits and challenges related to potable water reuse. It does not intend to be exhaustive, but to indicate the most relevant issues in both cases.

Potable water reuse schemes are subject to stringent regulations. They follow risk assessment and drinking water safety plans, which include pilot studies, process control considerations, standards, monitoring and auditing of water quality, consideration of stakeholders and public perceptions and risk minimisation, among other factors. Treatment technologies used are advanced and require membrane filtration and ultraviolet disinfection to remove or destroy viruses, bacteria, chemicals, and other constituents of concern as part of the process of converting wastewater into a clean, safe source of municipal drinking water. Reused water is thus cleaner, and safer, than river flows in many cities, especially in the developing world, where improperly treated (or, more commonly, untreated) wastewater is normally discharged.

Potable water reuse and the SDG for water and sanitation

Proper treatment of wastewater and safe reuse are prerequisites if the main targets of Goal 6 are to be reached by 2030. Failure to achieve this goal will mean that health and living conditions of billions of people will suffer, as they have suffered until now, or even more, as populations are growing and water resources are scarcer and more polluted.

Wastewater that is treated and safely reused for potable purposes becomes a new source of water that can be supplied to growing populations. Examples mentioned earlier show that there are thousands of people with access to clean water due to potable water reuse. This is water that would not be available otherwise. Potable water reuse has become more relevant during drought periods when populations with access to reused water have not suffered of water rationing, while people elsewhere without this alternative have not had the same opportunity.

Potable water reuse represents a reliable alternative way to produce safe water, improve the quality of water in receiving water bodies, and mitigate water scarcity for all uses, contributing to the SDG on clean water and sanitation. More broadly, to improve overall quality of life. However, such projects alone cannot enable the achievement of SDG 6, and produce all the safe water the world is running short of at present and will need in the future. As argued earlier, water reuse is part of comprehensive water planning and management strategies.

Water scarcity needs to be approached holistically. At present and looking towards the future, when demands for safe water will be more pressing and water resources will be less available than now, all alternatives for water supply must be considered, potable water reuse included.

The study followed a three-method approach. The first was literature review and analysis to understand the range of issues that determine the extent of the contributions of water reuse towards the realisation of clean water and sanitation Sustainable Development Goals in specific, and to the progress of several other non-water related SDGs positively influencing quality of life. Following the review and analysis, the second approach was the discussion of water reuse projects that have been operational for decades and that have rendered numerous benefits to the population in terms of safe water and sanitation, as well as projects that have been halted due to health concerns and insufficient involvement of the public. Finally, the most recent initiatives to strengthen and diversity the water resources available at the national level, e.g., United States, are presented to emphasise the fundamental role of water reuse towards fulfilment of the SDGs on clean water and sanitation.

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UK Water Industry Research Limited. A Protocol for Developing Water Reuse Criteria with Reference for Drinking Water Supplies , https://www.waterboards.ca.gov/water_issues/programs/grants_loans/water_recycling/research/02_011.pdf (2005).

California Water Resources Control Boards. Recommendations of the Advisory Group on the Feasibility of Developing Uniform Water Criteria for Direct Potable Reuse , https://www.waterboards.ca.gov/drinking_water/certlic/drinkingwater/rw_dpr_criteria.html (2020).

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Acknowledgements

This research was funded by the Institute of Water Policy, Lee Kuan Yew School of Public Policy, National University of Singapore. Grant R-603-000-289-490.

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The City of Tomorrow Will Run on Your Toilet Water

toilet water

The residents of the 40 floors of San Francisco apartments above our heads may live in luxury, but really, they’re just like the rest of us: showering, washing their hands, doing laundry. Normally in the US, all their water would flush out to a treatment facility, and eventually out to a body of water; 34 billion gallons of wastewater is processed this way across the country every day. But with multiple problems for cities now converging— extreme heat , water shortages, and rapid population growth—increasingly scientists are finding clever ways to extract more use from water that’s flushed away.

In this basement, a company called Epic Cleantec intercepts the building’s gray water (dirty water that doesn’t contain human waste or food scraps) and passes it through tanks and a maze of pipes for fine filtration and disinfection with chlorine and UV light. The resulting liquid is then piped back upstairs to fill toilets and urinals, taking at least some of the “waste” out of wastewater.

“By regulation, we’re only reusing the water for nonpotable applications,” says Aaron Tartakovsky, cofounder and CEO of Epic Cleantec. “Scientifically, we can produce drinking-water quality.” Indeed, the company brewed a beer with its recycled water from this building. (A kölsch, if you were curious.) “We’re turning wastewater—which in my opinion, is a term that is in dire need of a rebrand—into clean water, into renewable energy, and into soil,” says Tartakovsky.

Theoretically, the used water that flows out of your home contains 10 times the amount of energy it takes for a treatment facility to process it. It’s also rich in valuable nutrients and minerals, says Peter Grevatt, CEO of the Water Research Foundation, a US nonprofit supported by water utilities. And so as well as recycling water, Epic Cleantec is experimenting with heat exchangers that can extract energy from a building’s wastewater and use it to warm up the water going back upstairs, thus reducing utility bills. The company is also developing a system that processes residents’ black water—which includes human waste and food organics from kitchen sinks and dishwashers—into a soil amendment.

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Across the street from this apartment building, in Epic Cleantec’s offices, Tartakovsky grabs a handful of the stuff, which has been treated to remove pathogens. “You can touch it, smell it, whatever you’re comfortable with,” Tartakovsky says. (I do both—it feels and smells like compost.)

This sort of water reuse is happening increasingly at a municipal level, too, with state-of-the-art facilities recycling water instead of releasing it all into nature. What Epic Cleantec has achieved is to essentially shrink down what a water recycling plant does into a system that fits in a high-rise basement, lightening the burden on municipal wastewater treatment and reducing pressure on water supplies.

Whatever the system, water recycling will to need to ramp up massively in the coming decades. Today 56 percent of humanity lives in cities, but that’ll jump to 70 percent by 2050 . Cities suck up a whole lot of water, especially as their populations get richer (and therefore more wasteful) and urban industrial activity increases. All the while, climate change is drying out many of the places people are flocking to, like the southwestern US. “You look to the places that are already experiencing the greatest level of water stress, many of those places are the places that are most rapidly growing,” says Grevatt. “Needing to figure out how we recover resources is incredibly important.”

A recent study laid out the surprising dynamics of how this urban growth will unfold. Greenhouse gases scale sublinearly as a city grows, meaning at a slower rate than the population increases, due in part to efficiencies around things like public transportation. Solid waste, which ends up in a landfill, scales linearly, meaning it increases in lockstep with changes to the human population. Wastewater, though, scales super linearly, so it grows at a faster rate than a growing population.

Put another way: The bigger a city gets, the more wasteful it gets with water, even though its energy usage becomes more efficient. “We had a hard time figuring out why ,” says New York University industrial ecologist Mingzhen Lu, coauthor of the study. “The best explanation we came up with is there could be a strong link with wealth creation, which in itself is superlinear with city size. Any dollar we generate as a human society, we consume water. On the other side, when you have more wealth, there might be an argument that you will use more water more lavishly.”

As urban water use grows, the risk is continuing with wastewater treatment as usual: pumping the stuff into the environment. “I think that will be one of the things future societies think is most crazy about the last few hundred years, is that we just dumped wastewater into the ocean rather than pumping it back into the farmland,” says Santa Fe Institute theoretical physical biologist Chris Kempes, coauthor of the paper.

sample of water in jars

The input to the system operated by Epic Cleantec in the San Francisco building, versus the output.

The technology to extract fresh water from wastewater has existed for decades. In San Diego, which has been recycling water since 1981, two water reclamation plants together produce 21 million gallons of water every day (on a yearly average), with more capacity being added in the coming years. Technically, that water isn’t considered potable, so it’s used for agriculture and industry. But in 2026, San Diego will start delivering drinking water, thanks to even more advanced purification techniques: Wastewater is hit with ozone, killing bacteria and viruses, then passes through filters and then through ultrafine membranes with pores so small, basically only water molecules can get through . They’ll eventually ramp up to produce 30 million gallons of water daily, aiming to provide half the city’s drinking water this way by 2035.

While this process is expensive—it costs a lot to build out the facilities to process the water and takes a lot of energy to shove liquid through such fine membranes—the technology is maturing and costs are falling. “What’s really wild is we’ve had visitors from other agencies and areas that are water- rich ,” says Juan Guerreiro, San Diego’s director of public utilities. “You wouldn't think they’d want to push towards these projects. But what they’re realizing is that recycling the water that we already have contained within our wastewater systems, from an environmental stewardship perspective, is really beneficial.” Recycling can help reduce demand for river water, for example, thus protecting the fish species there.

The trickier half of wastewater recycling is the solid human waste that facilities accumulate as biosolids, or sludge. In the US , 56 percent of sludge produced is applied to the land, 27 percent is dumped in landfills, and 16 percent is incinerated. In addition to all the carbon from the food we eat, sludge is infused with chemicals that we (and industries) flush down the drain.

In 2022, Maine banned the use of sludge as fertilizer due to contamination with PFAS, a group of chemicals linked to cancers and hormonal problems. Sludge is also notoriously loaded with microplastics: When we do a load of laundry, millions of synthetic fibers break off and wash into a wastewater facility . Sludge applied to fields turns out to be a major source of microplastics corrupting the environment.

The industry is researching ways to isolate these contaminants, Grevatt says, both so it can keep them from the environment and to safely unlock the potential of our waste carbon and nutrients. “It’s extraordinarily challenging,” says Grevatt. “Wastewater treatment operations are not the producers, but they are recipients of PFAS from all kinds of different sources.”

An alternative option to sludge is biochar. If you heat that organic matter in a special chamber, a process known as pyrolysis, it turns to concentrated carbon. Startups have been doing this with agricultural waste, like corn stalks, to create charcoal and oil that they bury underground . (As those plants grew, they sequestered carbon, so in this case you’d actually be removing carbon from the atmosphere by putting it back in the earth.) Farmers are also sprinkling biochar on their fields, which can improve crop yields and add carbon to soils.

hand holding soil dirt

Epic Cleantec's soil amendment

Researchers are experimenting with using the same technique for wastewater solids, basically turning sludge into a solid product. “If you do pyrolysis—because it’s thermochemical, it’s a heated process—you kill these bacteria, kill these pathogens, kill these viruses. It’s much cleaner,” says engineer Fengqi You, who studies wastewater at Cornell University. In addition, sludge is a heavy, unwieldy liquid to ship from facility to farm. “You transport a lot of water in that, and the density is low. But biochar, it’s light—you can put it in bags—making transport easier.” So producers could ship it off more easily to faraway farms, but also distribute it more locally, to urban farms closer to the source of wastewater.

A wastewater facility can also create fuel in oxygen-free chambers, where microbes eat the solid waste and release methane “biogas” as a byproduct. “This biogas can be burned to generate heat,” says You. In Ithaca, New York, that can fully power a wastewater facility itself, but You has also been experimenting with using biogas to heat nearby buildings, including a medical center. Heating a building with natural gas adds carbon emissions to the atmosphere, but as biogas comes from the crops we eat and poop into the sewer system, which grew by drawing down carbon from the atmosphere, so burning it forms a carbon loop.

Before those microbes create biogas, they also generate volatile fatty acids. These could be made into jet fuel, or maybe even a fuel for fleets of city vehicles, says environmental engineer Sybil Sharvelle, who studies wastewater at Colorado State University. “There’s a lot of value in all sorts of those volatile fatty acids,” says Sharvelle.

In addition to using the waste solids as compost, like Epic Cleantec is experimenting with, Sharvelle notes that urban farms could benefit from using recycled wastewater that’s been disinfected for use on crops, but with the nitrogen and phosphorus left in. Those are essential nutrients for plants, but are actually difficult to remove from water. “If you can leave nitrogen and phosphorus in the system, that’s a much more energy-efficient way to just make use of those nutrients directly,” says Sharvelle.

All told, the linear path of water—from source to city to sea—is starting to curve. The future of wastewater is circular, recycling back into drinking water, compost for urban farms, and energy. Far from being unnatural, drinking repurposed toilet water is the kind of resourcefulness that nature intended. “Recycling is ubiquitous in nature,” says Kempes. “If there’s an untapped source of energy or nutrients, someone finds a way to use it. If you can create a fertilizer, find a way to clean water, and produce heat and electricity at the same time, that mirrors what we’ve seen biology evolve to do over billions of years.”

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Why Is it Important to Recycle Water?

Why Is it Important to Recycle Water?

Pros & Cons of Recycling Water

Water that is on the Earth today is the same water that was here when the Earth began. This is possible because of recycled water, both naturally occurring and as a result of human technology. The Earth naturally reuses its water; however, water recycling in the human population uses technology to speed up the process through practices like reusing waste water for purposes such as irrigation, flushing a toilet or filling up a groundwater basin. Another common form of water recycling is industrial recycling, where an industrial facility will reuse "waste" water on site for processes such as cooling. One of the key advantages of recycling water is that it reduces the need for water to be removed from natural habitats such as wetlands.

Environmental Benefits of Recycling Water

When you recycle the water that you use in your area, this means that you do not have to take water from other areas. Many areas where pure water is plentiful are delicate ecosystems that suffer when their water is removed. When the water is recycled, it makes it easy for places like the wetlands to keep their water supplies.

More Advantages of Recycling Wastewater

Many times, recycling water not only prevents its removal from sensitive environments, but it keeps wastewater from going into bodies of water such as ocean or rivers. Recycling water takes wastewater such as sewage and reuses it, instead of routing it directly into the nearest river or ocean where it could spread pollution and disrupt the aquatic life.

Increases Irrigation Benefits

While wastewater can be severely damaging to rivers and oceans, the Environmental Protection Agency advises that recycled water often contains properties that are extremely beneficial to irrigating and fertilizing fields. Recycled water often contains high levels of nitrogen, which, while bad for aquatic life, is a required nutrient for plants.

Improves Wetlands

The wetlands provide many benefits to the environment, such as housing wildlife, diminishing floods, improving the quality of the water and providing a safe breeding ground for fish populations. Many times, recycled water can be added to the dried wetlands, helping them to once again thrive into a lush habitat.

Provides Future Water Supply

When you take water from the rivers and oceans to use for things such as irrigation and wetlands, you use up part of the drinking water supply. When you recycle water and use that instead, you minimize the potential loss of drinking water. This leaves the maximum amount of water possible for future generations to use for their drinking needs.

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About the Author

Allison Michelle holds a degree in journalism from Patrick Henry College. Her writing has appeared in the Loudoun-Times Mirror, Patrol Magazine and the Washington Post's Loudoun Extra.

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Water Recycling

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Table of Contents

Introduction

The world is currently in dire need for sustainable water sources. Currently, it is estimated that over 1 billion people lack access to clean water (Rodriguez et.al, 2009). The growing water deficiency can be attributed to climate change that causes erratic weather, declining freshwater sources, and the abuse and misuse of water. Growing populations also serve to heighten the demand for water, especially in urban areas. A shortage of water on a large-scale would subsequently lead to food scarcity and a health crisis, with profound economic, social and environmental impacts. Recycling water, as opposed to utilizing fresh water is an efficient water-saving measure and part of sustainable water management.

essay on water recycling

The Water Recycling Process

The water recycling process employs very basic chemical, biological, and physical technologies eradicate contaminants. Primary treatment involves the use physical water treatment systems. Secondary treatment involves the use biological processes to further treat water (Integrated Water Strategies, 2007).  The water treatment process is a very important one because of the high demand and use of water. The process involves the filtration of wastes from home and business use to be returned into the water grid. This process is vital since because much water is used daily for domestic use without considering the water from agriculture and industrial use. Thus, clean water is crucial, and since most of the water is salty, the recycling and reuse process is crucial to preserving a healthy future.

The first process of water recycling is filtration where it passes through a screen. The aim is to get rid of solid and very large objects such as stones and plastics that can compromise the cleaning equipment. Next, it passes through a grit chamber for removal of grit. Grit can comprise things like tiny rock particles and sediments. After the removal of grit, there is presence of other impurities such as particles. The particles are removed in a sedimentation tank. The heap of solids and particles that gather at the bottom of the sedimentation tank are called bio-solids previously sludge (Lenntech, 2008). This material can either be reused as fertilizers. This is the conclusion of the primary treatment.

essay on water recycling

There is an increase in the demand for clean water in many cities. The primary treatment is not usually enough to recycle water into perfectly clean. Thus, the secondary treatment is crucial in this stage. This process is used to kill water microorganisms in the water. In this process, a trickling bed is fitted where water flows. The bed is usually made up of a heap of stones, but it can be other artificial material like as plastics. The bacterium builds on the stones and ingests organic matter in the water. This process removes 85% of the organic impurities. However, it is obsolete and is substituted with the activated sludge process. It involves water into air and sludge filled with bacteria. The water is transferred to another sedimentation tank, which chlorinated to completely kill 99% of the bacteria (Eckhardt, 2008).

Research Notes the Paper is Based

This paper is based on research process as noted by (Rodriguez et.al, 2009) of recycling effluent (sewage and wastewater) is designed to mirror what happens in nature but at an accelerated rate. The process is undertaken both biologically (by microorganisms and bacteria) and physically (through ultrafiltration and rapid sand filtration). Wastewater that is intended for drinking goes through advanced purification processes to ensure it is free of contaminants. The specific process of wastewater treatment differs from plant to plant but in order to fully purify wastewater a number of barrier treatments are used. These include ozonation, dissolved air flotation, chlorination, activated carbon filtration, and enhanced coagulation (Rodriguez et.al, 2009). The wastewater is also taken through modern technologies in the process of purification such as reverse osmosis where water particles are separated from impurities, and ultraviolet disinfection which imitates the natural ultraviolet light that purifies water. To fully understand how recycled sewage water can be part of our daily lives, a case study was analyzed where the process has been successfully applied. Namibia, a small landlocked country in the south of Africa with a population of just over 2 million, was actually the first country to implement recycled sewage water for consumption in 1968 in the outskirts of its capital city Windhoek (Gross, 2016). For the past 50 years, Namibia has taken sewage and turned it into drinkable water, long before any other nation had fathomed such a concept. Today, the plant processes over 40,000 cubic meters of sewage a day a lot more than it was initially intended for. Apart from the strong pungent smell that the waste treatment plant emits, it has no other visible social or environmental bearings on the surrounding area (Gross, 2016).

essay on water recycling

In conclusion, the process of treating water is an important one for everyone. People that lack clean water are vulnerable to waterborne diseases. Clean water is a necessity to maintaining good health. The complex process of recycling is crucial to maintain a clean and fresh supply of water to households, agriculture, and industries.

  • Eckhardt, G. (2008). “Water Recycling” The Edwards Aquifer Website.
  • Gross, D. (2016). A. “Recycling sewage into drinking water is no big deal. They’ve been doing it in Namibia for 50 years.” Public Radio International – Science, Tech & Environment. Website. 31 March 2017.
  • Integrated Water Strategies. (2007). “Wastewater Basics” Design for Nature by Nature.
  • Lenntech Water Recycling. (2008). “The Re-use of Process and Waste Water” Lenntech Water Recycling.
  • Leong, C. (2016). “The Role of Emotions in Drinking Recycled Water.” Water, 8(11) 548.
  • Rodriguez, Clemencia, et al. (2009). “Indirect Potable Reuse: A Sustainable Water Supply Alternative.” Sustainability: Environmental Studies and Public Health. 1174-1203.
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Wastewater Treatment and Reuse: a Review of its Applications and Health Implications

  • Open access
  • Published: 10 May 2021
  • Volume 232 , article number  208 , ( 2021 )

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  • Kavindra Kumar Kesari   ORCID: orcid.org/0000-0003-3622-9555 1   na1 ,
  • Ramendra Soni 2   na1 ,
  • Qazi Mohammad Sajid Jamal 3 ,
  • Pooja Tripathi 4 ,
  • Jonathan A. Lal 2 ,
  • Niraj Kumar Jha 5 ,
  • Mohammed Haris Siddiqui 6 ,
  • Pradeep Kumar 7 ,
  • Vijay Tripathi 2 &
  • Janne Ruokolainen 1  

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Water scarcity is one of the major problems in the world and millions of people have no access to freshwater. Untreated wastewater is widely used for agriculture in many countries. This is one of the world-leading serious environmental and public health concerns. Instead of using untreated wastewater, treated wastewater has been found more applicable and ecofriendly option. Moreover, environmental toxicity due to solid waste exposures is also one of the leading health concerns. Therefore, intending to combat the problems associated with the use of untreated wastewater, we propose in this review a multidisciplinary approach to handle wastewater as a potential resource for use in agriculture. We propose a model showing the efficient methods for wastewater treatment and the utilization of solid wastes in fertilizers. The study also points out the associated health concern for farmers, who are working in wastewater-irrigated fields along with the harmful effects of untreated wastewater. The consumption of crop irrigated by wastewater has leading health implications also discussed in this review paper. This review further reveals that our current understanding of the wastewater treatment and use in agriculture with addressing advancements in treatment methods has great future possibilities.

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1 Introduction

Rapidly depleting and elevating the level of freshwater demand, though wastewater reclamation or reuse is one of the most important necessities of the current scenario. Total water consumption worldwide for agriculture accounts 92% (Clemmens et al., 2008 ; Hoekstra & Mekonnen, 2012 ; Tanji & Kielen, 2002 ). Out of which about 70% of freshwater is used for irrigation (WRI, 2020 ), which comes from the rivers and underground water sources (Pedrero et al., 2010 ). The statistics shows serious concern for the countries facing water crisis. Shen et al. ( 2014 ) reported that 40% of the global population is situated in heavy water–stressed basins, which represents the water crisis for irrigation. Therefore, wastewater reuse in agriculture is an ideal resource to replace freshwater use in agriculture (Contreras et al., 2017 ). Treated wastewater is generally applied for non-potable purposes, like agriculture, land, irrigation, groundwater recharge, golf course irrigation, vehicle washing, toilet flushes, firefighting, and building construction activities. It can also be used for cooling purposes in thermal power plants (Katsoyiannis et al., 2017 ; Mohsen, 2004 ; Smith, 1995 ; Yang et al., 2017 ). At global level, treated wastewater irrigation supports agricultural yield and the livelihoods of millions of smallholder farmers (Sato et al., 2013 ). Global reuse of treated wastewater for agricultural purposes shows wide variability ranging from 1.5 to 6.6% (Sato et al., 2013 ; Ungureanu et al., 2018 ). More than 10% of the global population consumes agriculture-based products, which are cultivated by wastewater irrigation (WHO, 2006 ). Treated wastewater reuse has experienced very rapid growth and the volumes have been increased ~10 to 29% per year in Europe, the USA, China, and up to 41% in Australia (Aziz & Farissi, 2014 ). China stands out as the leading country in Asia for the reuse of wastewater with an estimated 1.3 M ha area including Vietnam, India, and Pakistan (Zhang & Shen, 2017 ). Presently, it has been estimated that, only 37.6% of the urban wastewater in India is getting treated (Singh et al., 2019 ). By utilizing 90% of reclaimed water, Israel is the largest user of treated wastewater for agriculture land irrigation (Angelakis & Snyder, 2015 ). The detail information related to the utilization of freshwater and treated wastewater is compiled in Table 1 .

Many low-income countries in Africa, Asia, and Latin America use untreated wastewater as a source of irrigation (Jiménez & Asano, 2008 ). On the other hand, middle-income countries, such as Tunisia, Jordan, and Saudi Arabia, use treated wastewater for irrigation (Al-Nakshabandi et al., 1997 ; Balkhair, 2016a ; Balkhair, 2016b ; Qadir et al., 2010 ; Sato et al., 2013 ).

Domestic water and treated wastewater contains various type of nutrients such as phosphorus, nitrogen, potassium, and sulfur, but the major amount of nitrogen and phosphorous available in wastewater can be easily accumulated by the plants, that’s why it is widely used for the irrigation (Drechsel et al., 2010 ; Duncan, 2009 ; Poustie et al., 2020 ; Sengupta et al., 2015 ). The rich availability of nutrients in reclaimed wastewater reduces the use of fertilizers, increases crop productivity, improves soil fertility, and at the same time, it may also decrease the cost of crop production (Chen et al., 2013 a; Jeong et al., 2016 ). The data of high nutritional values in treated wastewater is shown in Fig. 1 .

figure 1

Nutrient concentrations (mg/L) of freshwater/wastewater (Yadav et al., 2002 )

Wastewater reuse for crop irrigation showed several health concerns (Ungureanu et al., 2020 ). Irrigation with the industrial wastewater either directly or mixing with domestic water showed higher risk (Chen et al., 2013). Risk factors are higher due to heavy metal and pathogens contamination because heavy metals are non-biodegradable and have a long biological half-life (Chaoua et al., 2019 ; WHO, 2006 ). It contains several toxic elements, i.e., Cu, Cr, Mn, Fe, Pb, Zn, and Ni (Mahfooz et al., 2020 ). These heavy metals accumulate in topsoil (at a depth of 20 cm) and sourcing through plant roots; they enter the human and animal body through leafy vegetables consumption and inhalation of contaminated soils (Mahmood et al., 2014 ). Therefore, health risk assessment of such wastewater irrigation is important especially in adults (Mehmood et al., 2019 ; Njuguna et al., 2019 ; Xiao et al., 2017 ). For this, an advanced wastewater treatment method should be applied before release of wastewater in the river, agriculture land, and soils. Therefore, this review also proposed an advance wastewater treatment model, which has been tasted partially at laboratory scale by Kesari and Behari ( 2008 ), Kesari et al. ( 2011a , b ), and Kumar et al. ( 2010 ).

For a decade, reuse of wastewater has also become one of the global health concerns linking to public health and the environment (Dang et al., 2019 ; Narain et al., 2020 ). The World Health Organization (WHO) drafted guidelines in 1973 to protect the public health by facilitating the conditions for the use of wastewater and excreta in agriculture and aquaculture (WHO, 1973 ). Later in 2005, the initial guidelines were drafted in the absence of epidemiological studies with minimal risk approach (Carr, 2005 ). Although, Adegoke et al. ( 2018 ) reviewed the epidemiological shreds of evidence and health risks associated with reuse of wastewater for irrigation. Wastewater or graywater reuse has adverse health risks associated with microbial hazards (i.e., infectious pathogens) and chemicals or pharmaceuticals exposures (Adegoke et al., 2016 ; Adegoke et al., 2017 ; Busgang et al., 2018 ; Marcussen et al., 2007 ; Panthi et al., 2019 ). Researchers have reported that the exposure to wastewater may cause infectious (helminth infection) diseases, which are linked to anemia and impaired physical and cognitive development (Amoah et al., 2018 ; Bos et al., 2010 ; Pham-Duc et al., 2014 ; WHO, 2006 ).

Owing to an increasing population and a growing imbalance in the demand and supply of water, the use of wastewater has been expected to increase in the coming years (World Bank, 2010 ). The use of treated wastewater in developed nations follows strict rules and regulations. However, the direct use of untreated wastewater without any sound regulatory policies is evident in developing nations, which leads to serious environmental and public health concerns (Dickin et al., 2016 ). Because of these issues, we present in this review, a brief discussion on the risk associated with the untreated wastewater exposures and advanced methods for its treatment, reuse possibilities of the treated wastewater in agriculture.

2 Environmental Toxicity of Untreated Wastewater

Treated wastewater carries larger applicability such as irrigation, groundwater recharge, toilet flushing, and firefighting. Municipal wastewater treatment plants (WWTPs) are the major collection point for the different toxic elements, pathogenic microorganisms, and heavy metals. It collects wastewater from divergent sources like household sewage, industrial, clinical or hospital wastewater, and urban runoff (Soni et al., 2020 ). Alghobar et al. ( 2014 ) reported that grass and crops irrigated with sewage and treated wastewater are rich in heavy metals in comparison with groundwater (GW) irrigation. Although, heavy metals classified as toxic elements and listed as cadmium, lead, mercury, copper, and iron. An exceeding dose or exposures of these heavy metals could be hazardous for health (Duan et al., 2017 ) and ecological risks (Tytła, 2019 ). The major sources of these heavy metals come from drinking water. This might be due to the release of wastewater into river or through soil contamination reaches to ground water. Table 2 presenting the permissible limits of heavy metals presented in drinking water and its impact on human health after an exceeding the amount in drinking water, along with the route of exposure of heavy metals to human body.

Direct release in river or reuse of wastewater for irrigation purposes may create short-term implications like heavy metal and microbial contamination and pathogenic interaction in soil and crops. It has also long-term influence like soil salinity, which grows with regular use of untreated wastewater (Smith, 1995 ). Improper use of wastewater for irrigation makes it unsafe and environment threatening. Irrigation with several different types of wastewater, i.e., industrial effluents, municipal and agricultural wastewaters, and sewage liquid sludge transfers the heavy metals to the soil, which leads to accumulation in crops due to improper practices. This has been identified as a significant route of heavy metals into aquatic resources (Agoro et al., 2020 ). Hussain et al. ( 2019 ) investigated the concentration of heavy metals (except for Cd) was higher in the soil irrigated with treated wastewater (large-scale sewage treatment plant) than the normal ground water, also reported by Khaskhoussy et al. ( 2015 ).

In other words, irrigation with wastewater mitigates the quality of crops and enhances health risks. Excess amount of copper causes anemia, liver and kidney damage, vomiting, headache, and nausea in children (Bent & Bohm, 1995 ; Madsen et al., 1990 ; Salem et al., 2000 ). A higher concentration of arsenic may lead to bone and kidney cancer (Jarup, 2003 ) and results in osteopenia or osteoporosis (Puzas et al., 2004 ). Cadmium gives rise to musculoskeletal diseases (Fukushima et al., 1970 ), whereas mercury directly affects the nervous system (Azevedo et al., 2014 ).

3 Spread of Antibiotic Resistance

Currently, antibiotics are highly used for human disease treatment; however, uses in poultries, animal husbandries, biochemical industries, and agriculture are common practices these days. Extensive use and/or misuse of antibiotics have given rise to multi-resistant bacteria, which carry multiple resistance genes (Icgen & Yilmaz, 2014 ; Lv et al., 2015 ; Tripathi & Tripathi, 2017 ; Xu et al., 2017 ). These multidrug-resistant bacteria discharged through the sewage network and get collected into the wastewater treatment plants. Therefore, it can be inferred that the WWTPs serve as the hotspot of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs). Though, these antibiotic-resistant bacteria can be disseminated to the different bacterial species through the mobile genetic elements and horizontal gene transfer (Gupta et al., 2018 ). Previous studies indicated that certain pathogens might survive in wastewater, even during and after the treatment processes, including methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE) (Börjesson et al., 2009 ; Caplin et al., 2008 ). The use of treated wastewater in irrigation provides favorable conditions for the growth and persistence of total coliforms and fecal coliforms (Akponikpe et al., 2011 ; Sacks & Bernstein, 2011 ). Furthermore, few studies have also reported the presence of various bacterial pathogens, such as Clostridium , Salmonella , Streptococci , Viruses, Protozoa, and Helminths in crops irrigated with treated wastewater (Carey et al., 2004 ; Mañas et al., 2009 ; Samie et al., 2009 ). Goldstein ( 2013 ) investigated the survival of ARB in secondary treated wastewater and proved that it causes serious health risks to the individuals, who are exposed to reclaimed water. The U.S. Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO) have already declared the ARBs as the imminent hazard to human health. According to the list published by WHO, regarding the development of new antimicrobial agents, the ESKAPE ( Enterococcus faecium , S. aureus , Klebsiella pneumoniae , Acinetobacter baumannii , Pseudomonas aeruginosa , and Enterobacter species) pathogens were designated to be “priority status” as their occurrence in the food chain is considered as the potential and major threat for the human health (Tacconelli et al., 2018 ).

These ESKAPE pathogens have acquired the multi drug resistance mechanisms against oxazolidinones, lipopeptides, macrolides, fluoroquinolones, tetracyclines, β-lactams, β-lactam–β-lactamase inhibitor combinations, and even those antibiotics that are considered as the last line of defense, including carbapenems and glycopeptides (Giddins et al., 2017 ; Herc et al., 2017 ; Iguchi et al., 2016 ; Naylor et al., 2018 ; Zaman et al., 2017 ), by the means of genetic mutation and mobile genetic elements. These cluster of ESKAPE pathogens are mainly responsible for lethal nosocomial infections (Founou et al., 2017 ; Santajit & Indrawattana, 2016 ).

Due to the wide application of antibiotics in animal husbandry and inefficient capability of wastewater treatment plants, the multidrug-resistant bacteria such as tetracyclines, sulfonamides, β-lactam, aminoglycoside, colistin, and vancomycin in major are disseminated in the receiving water bodies, which ultimately results in the accumulation of ARGs in the irrigated crops (He et al., 2020 ).

4 Toxic Contaminations in Wastewater Impacting Human Health

The release of untreated wastewater into the river may pose serious health implications (König et al., 2017 ; Odigie, 2014 ; Westcot, 1997 ). It has been already discussed about the household and municipal sewage which contains a major amount of organic materials and pathogenic microorganisms and these infectious microorganisms are capable of spreading various diseases like typhoid, dysentery, diarrhea, vomiting, and malabsorption (Jia & Zhang, 2020 ; Numberger et al., 2019 ; Soni et al., 2020 ). Additionally, pharmaceutical industries also play a key role in the regulation and discharge of biologically toxic agents. The untreated wastewater also contains a group of contaminants, which are toxic to humans. These toxic contaminations have been classified into two major groups: (i) chemical contamination and (ii) microbial contamination.

4.1 Chemical Contamination

Mostly, various types of chemical compounds released from industries, tanneries, workshops, irrigated lands, and household wastewaters are responsible for several diseases. These contaminants can be organic materials, hydrocarbons, volatile compounds, pesticides, and heavy metals. Exposure to such contaminants may cause infectious diseases like chronic dermatoses and skin cancer, lung infection, and eye irritation. Most of them are non-biodegradable and intractable. Therefore, they can persist in the water bodies for a very long period and could be easily accumulated in our food chain system. Several pharmaceutical personal care products (PPCPs) and surfactants are available that may contain toxic compounds like nonylphenol, estrone, estradiol, and ethinylestradiol. These compounds are endocrine-disrupting chemicals (Bolong et al., 2009 ), and the existence of these compounds in the human body even in the trace amounts can be highly hazardous. Also, the occurrence of perfluorinated compounds (PFCs) in wastewater, which is toxic in nature, has been significantly reported worldwide (Templeton et al., 2009 ). Furthermore, PFCs cause severe health menaces like pre-eclampsia, birth defects, reduced human fertility (Webster, 2010 ), immunotoxicity (Dewitt et al., 2012 ), neurotoxicity (Lee & Viberg, 2013 ), and carcinogenesis (Bonefeld-Jorgensen et al., 2011 ).

4.2 Microbial Contamination

Researchers have reported serious health risks associated with the microbial contaminants in untreated wastewater. The diverse group of microorganisms causes severe health implications like campylobacteriosis, diarrhea, encephalitis, typhoid, giardiasis, hepatitis A, poliomyelitis, salmonellosis, and gastroenteritis (ISDH, 2009 ; Okoh et al., 2010 ). Few bacterial species like P. aeruginosa , Salmonella typhimurium , Vibrio cholerae , G. intestinales , Legionella spp., E. coli , Shigella sonnei have been reported for the spreading of waterborne diseases, and acute illness in human being (Craun et al., 2006 ; Craun et al., 2010 ). These aforementioned microorganisms may release in the environment from municipal sewage water network, animal husbandries, or hospitals and enter the food chain via public water supply systems.

5 Wastewater Impact on Agriculture

The agriculture sector is well known for the largest user of water, accounting for nearly 70% of global water usage (Winpenny et al., 2010 ). The fact that an estimated 20 million hectares worldwide are irrigated with wastewater suggests a major source for irrigation (Ecosse, 2001 ). However, maximum wastewater that is used for irrigation is untreated (Jiménez & Asano, 2008 ; Scott et al., 2004 ). Mostly in developing countries, partially treated or untreated wastewater is used for irrigation purpose (Scott et al., 2009 ). Untreated wastewater often contains a large range of chemical contaminants from waste sites, chemical wastes from industrial discharges, heavy metals, fertilizers, textile, leather, paper, sewage waste, food processing waste, and pesticides. World Health Organization (WHO) has warned significant health implications due to the direct use of wastewater for irrigation purposes (WHO, 2006 ). These contaminants pose health risks to communities (farmers, agricultural workers, their families, and the consumers of wastewater-irrigated crops) living in the proximity of wastewater sources and areas irrigated with untreated wastewater (Qadir et al., 2010 ). Wastewater also contains a wide variety of organic compounds. Some of them are toxic or cancer-causing and have harmful effects on an embryo (Jarup, 2003 ; Shakir et al., 2016 ). The pathway of untreated wastewater used in irrigation and associated health effects are shown in Fig. 2 .

figure 2

Exposure pathway representing serious health concerns from wastewater-irrigated crops

Alternatively, in developing countries, due to the limited availability of treatment facilities, untreated wastewater is discharged into the existing waterbodies (Qadir et al., 2010 ). The direct use of wastewater in agriculture or irrigation obstructs the growth of natural plants and grasses, which in turn causes the loss of biodiversity. Shuval et al. ( 1985 ) reported one of the earliest evidences connecting to agricultural wastewater reuse with the occurrence of diseases. Application of untreated wastewater in irrigation increases soil salinity, land sealing followed by sodium accumulation, which results in soil erosion. Increased soil salinity and sodium accumulation deteriorates the soil and decreases the soil permeability, which inhibits the nutrients intake of crops from the soil. These causes have been considered the long-term impact of wastewater reuse in agriculture (Halliwell et al., 2001 ). Moreover, wastewater contaminated soils are a major source of intestinal parasites (helminths—nematodes and tapeworms) that are transmitted through the fecal–oral route (Toze, 1997 ). Already known, the helminth infections are linked to blood deficiency and behavioral or cognitive development (Bos et al., 2010 ). One of the major sources of helminth infections around the world is the use of raw or partially treated sewage effluent and sludge for the irrigation of food crops (WHO, 1989 ). Wastewater-irrigated crops contain heavy metal contamination, which originates from mining, foundries, and metal-based industries (Fazeli et al., 1998 ). Exposure to heavy metals including arsenic, cadmium, lead, and mercury in wastewater-irrigated crops is a cause for various health problems. For example, the consumption of high amounts of cadmium causes osteoporosis in humans (Dickin et al., 2016 ). The uptake of heavy metals by the rice crop irrigated with untreated effluent from a paper mill has been reported to cause serious health concerns (Fazeli et al., 1998 ). Irrigating rice paddies with highly contaminated water containing heavy metals leads to the outbreak of Itai-itai disease in Japan (Jarup, 2003 ).

Owing to these widespread health risks, the WHO published the third edition of its guidelines for the safe use of wastewater in irrigating crops (WHO, 2006 ) and made recommendations for threshold contaminant levels in wastewater. The quality of wastewater for agricultural reuse have been classified based on the availability of nutrients, trace elements, microorganisms, and chemicals contamination levels. The level of contamination differs widely depending on the type of source, household sewage, pharmaceutical, chemical, paper, or textile industries effluents. The standard measures of water quality for irrigation are internationally reported (CCREM, 1987 ; FAO, 1985 ; FEPA, 1991 ; US EPA, 2004 , 2012 ; WHO, 2006 ), where the recommended levels of trace elements, metals, COD, BOD, nitrogen, and phosphorus are set at certain limits. Researchers reviewed the status of wastewater reuse for agriculture, based on its standards and guidelines for water quality (Angelakis et al., 1999 ; Brissaud, 2008 ; Kalavrouziotis et al., 2015 ). Based on these recommendations and guidelines, it is evident that greater awareness is required for the treatment of wastewater safely.

6 Wastewater Treatment Techniques

6.1 primary treatment.

This initial step is designed to remove gross, suspended and floating solids from raw wastewater. It includes screening to trap solid objects and sedimentation by gravity to remove suspended solids. This physical solid/liquid separation is a mechanical process, although chemicals can be used sometimes to accelerate the sedimentation process. This phase of the treatment reduces the BOD of the incoming wastewater by 20–30% and the total suspended solids by nearly 50–60%.

6.2 Secondary (Biological) Treatment

This stage helps eliminate the dissolved organic matter that escapes primary treatment. Microbes consume the organic matter as food, and converting it to carbondioxide, water, and energy for their own growth. Additional settling to remove more of the suspended solids then follows the biological process. Nearly 85% of the suspended solids and biological oxygen demand (BOD) can be removed with secondary treatment. This process also removes carbonaceous pollutants that settle down in the secondary settling tank, thus separating the biological sludge from the clear water. This sludge can be fed as a co-substrate with other wastes in a biogas plant to obtain biogas, a mixture of CH 4 and CO 2 . It generates heat and electricity for further energy distribution. The leftover, clear water is then processed for nitrification or denitrification for the removal of carbon and nitrogen. Furthermore, the water is passed through a sedimentation basin for treatment with chlorine. At this stage, the water may still contain several types of microbial, chemical, and metal contaminations. Therefore, to make the water reusable, e.g., for irrigation, it further needs to pass through filtration and then into a disinfection tank. Here, sodium hypochlorite is used to disinfect the wastewater. After this process, the treated water is considered safe to use for irrigation purposes. Solid wastes generated during primary and secondary treatment processes are processed further in the gravity-thickening tank under a continuous supply of air. The solid waste is then passed into a centrifuge dewatering tank and finally to a lime stabilization tank. Treated solid waste is obtained at this stage and it can be processed further for several uses such as landfilling, fertilizers and as a building.

Other than the activated sludge process of wastewater treatment, there are several other methods developed and being used in full-scale reactors such as ponds (aerobic, anaerobic, facultative, and maturation), trickling filters, anaerobic treatments like up-flow anaerobic sludge blanket (UASB) reactors, artificial wetlands, microbial fuel cells, and methanogenic reactors.

UASB reactors are being applied for wastewater treatment from a very long period. Behling et al. ( 1996 ) examined the performance of the UASB reactor without any external heat supply. In their study, the COD loading rate was maintained at 1.21 kg COD/m 3 /day, after 200 days of trial. They achieved an average of 85% of COD removal. Von-Sperling and Chernicharo ( 2005 ) presented a combined model consisted of an Up-flow Anaerobic Sludge Blanket-Activated Sludge reactor (UASB–AS system), using the low strength domestic wastewater with a BOD 5 amounting to 340 mg/l. Outcomes of their experiment have shown a 60% reduction in sludge construction and a 40% reduction in aeration energy consumption. In another experiment, Rizvi et al. ( 2015 ) seeded UASB reactor with cow manure dung to treat domestic wastewater; they observed 81%, 75%, and 76% reduction in COD, TSS, and total sulfate removal, respectively, in their results.

6.3 Tertiary or Advanced Treatment Processes

The tertiary treatment process is employed when specific constituents, substances, or contaminants cannot be completely removed after the secondary treatment process. The tertiary treatment processes, therefore, ensure that nearly 99% of all impurities are removed from wastewater. To make the treated water safe for drinking purposes, water is treated individually or in combination with advanced methods like the US (ultrasonication), UV (ultraviolet light treatment), and O 3 (exposure to ozone). This process helps to remove bacteria and heavy metal contaminations remaining in the treated water. For the purpose, the secondarily treated water is first made to undergo ultrasonication and it is subsequently exposed to UV light and passed through an ozone chamber for the complete removal of contaminations. The possible mechanisms by which cells are rendered inviable during the US include free-radical attack and physical disruption of cell membranes (Phull et al., 1997 ; Scherba et al., 1991 ). The combined treatment of US + UV + O 3 produces free radicals, which are attached to cell membranes of the biological contaminants. Once the cell membrane is sheared, chemical oxidants can enter the cell and attack internal structures. Thus, the US alone or in combination facilitates the deagglomeration of microorganisms and increases the efficiency of other chemical disinfectants (Hua & Thompson, 2000 ; Kesari et al., 2011a , b ; Petrier et al., 1992 ; Phull et al., 1997 ; Scherba et al., 1991 ). A combined treatment method was also considered by Pesoutova et al. ( 2011 ) and reported a very effective method for textile wastewater treatment. The effectiveness of ultrasound application as a pre-treatment step in combination with ultraviolet rays (Blume & Neis, 2004 ; Naddeo et al., 2009 ), or also compared it with various other combinations of both ultrasound and UV radiation with TiO 2 photocatalysis (Paleologou et al., 2007 ), and ozone (Jyoti & Pandit, 2004 ) to optimize wastewater disinfection process.

An important aspect of our wastewater treatment model (Fig. 3 ) is that at each step of the treatment process, we recommend the measurement of the quality of treated water. After ensuring that the proper purification standards are met, the treated water can be made available for irrigation, drinking or other domestic uses.

figure 3

A wastewater treatment schematic highlighting the various methods that result in a progressively improved quality of the wastewater from the source to the intended use of the treated wastewater for irrigation purposes

6.4 Nanotechnology as Tertiary Treatment of Wastewater Converting Drinking Water Alike

Considering the emerging trends of nanotechnology, nanofillers can be used as a viable method for the tertiary treatment of wastewater. Due to the very small pore size, 1–5-nm nanofillers may eliminate the organic–inorganic pollutants, heavy metals, as well as pathogenic microorganisms and pharmaceutically active compounds (PhACs) (Mohammad et al., 2015 ; Vergili, 2013 ). Over the recent years, nanofillers have been largely accepted in the textile industry for the treatment of pulp bleaching pharmaceutical industry, dairy industry, microbial elimination, and removal of heavy metals from wastewater (Abdel-Fatah, 2018 ). Srivastava et al. ( 2004 ) synthesized very efficient and reusable water filters from carbon nanotubes, which exhibited effective elimination of bacterial pathogens ( E. coli and S. aureus ), and Poliovirus sabin-1 from wastewater.

Nanofiltration requires lower operating pressure and lesser energy consumption in comparison of RO and higher rejection of organic compounds compared to UF. Therefore, it can be applied as the tertiary treatment of wastewater (Abdel-Fatah, 2018 ). Apart from nanofilters, there are various kinds of nanoparticles like metal nanoparticles, metal oxide nanoparticles, carbon nanotubes, graphene nanosheets, and polymer-based nanosorbents, which may play a different role in wastewater treatment based on their properties. Kocabas et al. ( 2012 ) analyzed the potential of different metal oxide nanoparticles and observed that nanopowders of TiO 2 , FeO 3 , ZnO 2 , and NiO can exhibit the exceeding amount of removal of arsenate from wastewater. Cadmium contamination in wastewater, which poses a serious health risk, can be overcome by using ZnO nanoparticles (Kumar & Chawla, 2014 ). Latterly, Vélez et al. ( 2016 ) investigated that the 70% removal of mercury from wastewater through iron oxide nanoparticles successfully performed. Sheet et al. ( 2014 ) used graphite oxide nanoparticles for the removal of nickel from wastewater. An exceeding amount of copper causes liver cirrhosis, anemia, liver, and kidney damage, which can be removed by carbon nanotubes, pyromellitic acid dianhydride (PMDA) and phenyl aminomethyl trimethoxysilane (PAMTMS) (Liu et al., 2010 ).

Nanomaterials are efficiently being used for microbial purification from wastewater. Carbon nanotubes (CNTs) are broadly applied for the treatment of wastewater contaminated with E. coli , Salmonella , and a wide range of microorganisms (Akasaka & Watari, 2009 ). In addition, silver nanoparticles reveal very effective results against the microorganisms present in wastewater. Hence, it is extensively being used for microbial elimination from wastewater (Inoue et al., 2002 ). Moreover, CNTs exhibit high binding affinity to bacterial cells and possess magnetic properties (Pan & Xing, 2008 ). Melanta ( 2008 ) confirmed and recommended the applicability of CNTs for the removal of E. coli contamination from wastewater. Mostafaii et al. ( 2017 ) suggested that the ZnO nanoparticles could be the potential antibacterial agent for the removal of total coliform bacteria from municipal wastewater. Apart from the previously mentioned, applicability of the nanotechnology, the related drawbacks and challenges cannot be neglected. Most of the nanoengineered techniques are currently either in research scale or pilot scale performing well (Gehrke et al., 2015 ). Nevertheless, as discussed above, nanotechnology and nanomaterials exhibit exceptional properties for the removal of contaminants and purification of water. Therefore, it can be adapted as the prominent solution for the wastewater treatment (Zekić et al., 2018 ) and further use for drinking purposes.

6.5 Wastewater Treatment by Using Plant Species

Some of the naturally growing plants can be a potential source for wastewater treatment as they remove pollutants and contaminants by utilizing them as a nutrient source (Zimmels et al., 2004 ). Application of plant species in wastewater treatment may be cost-effective, energy-saving, and provides ease of operation. At the same time, it can be used as in situ, where the wastewater is being produced (Vogelmann et al., 2016 ). Nizam et al. ( 2020 ) analyzed the phytoremediation efficiency of five plant species ( Centella asiatica , Ipomoea aquatica , Salvinia molesta , Eichhornia crassipes , and Pistia stratiotes ) and achieved the drastic decrease in the amount of three pollutants viz. total suspended solids (TSS), ammoniacal nitrogen (NH 3 -N), and phosphate levels . All the five species found to be efficient removal of the level of 63.9-98% of NH 3 -N, TSS, and phosphate. Coleman et al. ( 2001 ) examined the physiological effects of domestic wastewater treatment by three common Appalachian plant species: common rush or soft rush ( Juncus effuses L.), gray club-rush ( Scirpus Validus L.), and broadleaf cattail or bulrush ( Typha latifolia L.). They observed in their experiments about 70% of reduction in total suspended solids (TSS) and biochemical oxygen demand (BOD), 50% to 60% of reduction in nitrogen, ammonia, and phosphate levels, and a significant reduction in feacal coliform populations. Whereas, Zamora et al. ( 2019 ) found the removal efficiency of chemical oxygen demand (COD), total solids suspended (TSS), nitrogen as ammonium (N-NH 4 ) and nitrate (N-NO 3 ), and phosphate (P-PO 4 ) up to 20–60% higher using the three ornamental species of plants viz. Canna indica , Cyperus papyrus , and Hedychium coronarium . The list of various plant species applied for the wastewater treatment is shown in Table 3 .

6.6 Wastewater Treatment by Using Microorganisms

There is a diverse group of bacteria like Pseudomonas fluorescens , Pseudomonas putida , and different Bacillus strains, which are capable to use in biological wastewater systems. These bacteria work in the cluster forms as a floc, biofilm, or granule during the wastewater treatment. Furthermore, after the recognition of bacterial exopolysaccharides (EPS) as an efficient adsorption material, it may be applied in a revolutionary manner for the heavy metal elimination (Gupta & Diwan, 2017 ). There are few examples of EPS, which are commercially available, i.e., alginate ( P. aeruginosa , Azotobacter vinelandii ), gellan (Sphingomonas paucimobilis ), hyaluronan ( . aeruginosa , Pasteurella multocida , Streptococci attenuated strains ), xanthan (Xanthomonas campestris ), and galactopol ( Pseudomonas oleovorans ) (Freitas et al., 2009 ; Freitas, Alves, & Reis, 2011a ; Freitas, Alves, Torres, et al., 2011b ). Similarly, Hesnawi et al. ( 2014 ) experimented biodegradation of municipal wastewater using local and commercial bacteria (Sludge Hammer), where they achieved a significant decrease in synthetic wastewater, i.e., 70%, 54%, 52%, 42% for the Sludge Hammer, B. subtilis , B. laterosponus , and P. aeruginosa , respectively. Therefore, based on the above studies, it can be concluded that bioaugmentation of wastewater treatment reactor with selective and mixed strains can ameliorate the treatment. During recent years, microalgae have attracted the attention of researchers as an alternative system, due to their applicability in wastewater treatment. Algae are the unicellular or multicellular photosynthetic microorganism that grows on water surfaces, salt water, or moist soil. They utilize the exceeding amount of nutrients like nitrogen, phosphorus, and carbon for their growth and metabolism process through their anaerobic system. This property of algae also inhibits eutrophication; that is to avoid over-deposit of nutrients in water bodies. During the nutrient digestion process, algae produce oxygen that is constructive for the heterotrophic aerobic bacteria, which may further be utilized to degrade the organic and inorganic pollutants. Kim et al. ( 2014 ) observed a total decrease in the levels of COD (86%), total nitrogen (93%), and total phosphorus (83%) after using algae in the municipal wastewater consortium. Nmaya et al. ( 2017 ) reported the heavy metal removal efficiency of microalga Scenedesmus sp. from contaminated river water in the Melaka River, Malaysia. They observed the effective removal of Zn (97-99%) on the 3 rd and 7 th day of the experiment. The categorized list of microorganisms used for wastewater treatment is presented in Table 4 .

7 The Computational Approach in Wastewater Treatment

7.1 bioinformatics and genome sequencing.

A computational approach is accessible in wastewater treatment. Several tools and techniques are in use such as, sequencing platforms (Hall, 2007 ; Marsh, 2007 ), metagenome sequencing strategies (Schloss & Handelsman, 2005 ; Schmeisser et al., 2007 ; Tringe et al., 2005 ), bioinformatics tools and techniques (Chen & Pachter, 2005 ; Foerstner et al., 2006 ; Raes et al., 2007 ), and the genome analysis of complex microbial communities (Fig. 4 ). Most of the biological database contains microorganisms and taxonomical information. Thus, these can provide extensive details and supports for further utilization in wastewater treatment–related research and development (Siezen & Galardini, 2008 ). Balcom et al. ( 2016 ) explored that the microbial population residing in the plant roots immersed in the wastewater of an ecological WWTP and showed the evidence of the capacity for micro-pollutant biodegradation using whole metagenome sequencing (WMS). Similarly, Kumar et al. ( 2016 ) revealed that bioremediation of highly polluted wastewater from textile dyes by two novel strains were found to highly decolorize Joyfix Red. They were identified as Lysinibacillus sphaericus (KF032717) and Aeromonas hydrophila (KF032718) through 16S rDNA analysis. More recently, Leddy et al. ( 2018 ) reported that research scientists are making strides to advance the safety and application of potable water reuse with metagenomics for water quality analysis. The application of the bio-computational approach has also been implemented in the advancements of wastewater treatment and disease detection.

figure 4

A schematic showing the overall conceptual framework on which depicting the computational approach in wastewater treatment

7.2 Computational Fluid Dynamics in Wastewater Treatment

In recent years, computational fluid dynamics (CFD), a broadly used method, has been applied to biological wastewater treatment. It has exposed the inner flow state that is the hydraulic condition of a biological reactor (Peng et al., 2014 ). CFD is the application of powerful predictive modeling and simulation tools. It may calculate the multiple interactions between all the water quality and process design parameters. CFD modeling tools have already been widely used in other industries, but their application in the water industry is quite recent. CFD modeling has great applications in water and wastewater treatment, where it mechanically works by using hydrodynamic and mass transfer performance of single or two-phase flow reactors (Do-Quang et al., 1998 ). The level of CFD’s capability varies between different process units. It has a high frequency of application in the areas of final sedimentation, activated sludge basin modeling, disinfection, and greater needs in primary sedimentation and anaerobic digestion (Samstag et al., 2016 ). Now, researchers are enhancing the CFD modeling with a developed 3D model of the anoxic zone to evaluate further hydrodynamic performance (Elshaw et al., 2016 ). The overall conceptual framework and the applications of the computational approach in wastewater treatment are presented in Fig. 4 .

7.3 Computational Artificial Intelligence Approach in Wastewater Treatment

Several studies were obtained by researchers to implement computer-based artificial techniques, which provide fast and rapid automated monitoring of water quality tests such as BOD and COD. Recently, Nourani et al. ( 2018 ) explores the possibility of wastewater treatment plant by using three different kinds of artificial intelligence methods, i.e., feedforward neural network (FFNN), adaptive neuro-fuzzy inference system (ANFIS), and support vector machine (SVM). Several measurements were done in terms of effluent to tests BOD, COD, and total nitrogen in the Nicosia wastewater treatment plant (NWWTP) and reported high-performance efficiency of artificial intelligence (Nourani et al., 2018 ).

7.4 Remote sensing and Geographical Information System

Since the implementation of satellite technology, the initiation of new methods and tools became popular nowadays. The futuristic approach of remote sensing and GIS technology plays a crucial role in the identification and locating of the water polluted area through satellite imaginary and spatial data. GIS analysis may provide a quick and reasonable solution to develop atmospheric correction methods. Moreover, it provides a user-friendly environment, which may support complex spatial operations to get the best quality information on water quality parameters through remote sensing (Ramadas & Samantaray, 2018 ).

8 Applications of Treated Wastewater

8.1 scope in crop irrigation.

Several studies have assessed the impact of the reuse of recycled/treated wastewater in major sectors. These are agriculture, landscapes, public parks, golf course irrigation, cooling water for power plants and oil refineries, processing water for mills, plants, toilet flushing, dust control, construction activities, concrete mixing, and artificial lakes (Table 5 ). Although the treated wastewater after secondary treatment is adequate for reuse since the level of heavy metals in the effluent is similar to that in nature (Ayers & Westcot, 1985 ), experimental evidences have been found and evaluated the effects of irrigation with treated wastewater on soil fertility and chemical characteristics, where it has been concluded that secondary treated wastewater can improve soil fertility parameters (Mohammad & Mazahreh, 2003 ). The proposed model (Fig. 3 ) is tested partially previously at a laboratory scale by treating the wastewater (from sewage, sugar, and paper industry) in an ultrasonic bath (Kesari et al., 2011a , b ; Kesari & Behari, 2008 ; Kumar et al., 2010 ). Advancing it with ultraviolet and ozone treatment has modified this in the proposed model. A recent study shows that the treated water passed quality measures suited for crop irrigation (Bhatnagar et al., 2016 ). In Fig. 3 , a model is proposed including all three (UV, US, nanoparticle, and ozone) techniques, which have been tested individually as well as in combination (US and nanoparticle) (Kesari et al., 2011a , b ) to obtain the highest water quality standards acceptable for irrigation and even drinking purposes.

A wastewater-irrigated field is a major source of essential and non-essential metals contaminants such as lead, copper, zinc, boron, cobalt, chromium, arsenic, molybdenum, and manganese. While crops need some of these, the others are non-essential metals, toxic to plants, animals, and humans. Kanwar and Sandha ( 2000 ) reported that heavy metal concentrations in plants grown in wastewater-irrigated soils were significantly higher than in plants grown in the reference soil in their study. Yaqub et al. ( 2012 ) suggest that the use of US is very effective in removing heavy or toxic metals and organic pollutants from industrial wastewater. However, it has been also observed that the metals were removed efficiently, when UV light was combined with ozone (Samarghandi et al., 2007 ). Ozone exposure is a potent method for the removal of metal or toxic compounds from wastewater as also reported earlier (Park et al., 2008 ). Application of US, UV, and O 3 in combination lead to the formation of reactive oxygen species (ROS) that oxidize certain organics, metal ions and kill pathogens. In the process of advanced oxidizing process (AOP) primarily oxidants, electricity, light, catalysts etc. are implied to produce extremely reactive free radicals (such as OH) for the breakdown of organic matters (Oturan & Aaron, 2014 ). Among the other AOPs, ozone oxidization process is more promising and effective for the decomposition of complex organic contaminants (Xu et al., 2020 ). Ozone oxidizes the heavy metal to their higher oxidation state to form metallic oxides or hydroxides in which they generally form limited soluble oxides and gets precipitated, which are easy to be filtered by filtration process. Ozone oxidization found to be efficient for the removal of heavy metals like cadmium, chromium, cobalt, copper, lead, manganese, nickel, and zinc from the water source (Upadhyay & Srivastava, 2005 ). Ultrasonic-treated sludge leads to the disintegration of biological cells and kills bacteria in treated wastewater (Kesari, Kumar, et al., 2011a ; Kesari, Verma, & Behari, 2011b ). This has been found that combined treatment with ultrasound and nanoparticles is more effective (Kesari, Kumar, et al., 2011a ). Ultrasonication has the physical effects of cavitation inactivate and lyse bacteria (Broekman et al., 2010 ). The induced effect of US, US, or ozone may destroy the pathogens and especially during ultrasound irradiation including free-radical attack, hydroxyl radical attack, and physical disruption of cell membranes (Kesari, Kumar, et al., 2011a ; Phull et al., 1997 ; Scherba et al., 1991 ).

8.2 Energy and Economy Management

Municipal wastewater treatment plants play a major role in wastewater sanitation and public health protection. However, domestic wastewater has been considered as a resource or valuable products instead of waste, because it has been playing a significant role in the recovery of energy and resource for the plant-fertilizing nutrients like phosphorus and nitrogen. Use of domestic wastewater is widely accepted for the crop irrigation in agriculture and industrial consumption to avoid the water crisis. It has also been found as a source of energy through the anaerobic conversion of the organic content of wastewater into methane gas. However, most of the wastewater treatment plants are using traditional technology, as anaerobic sludge digestion to treat wastewater, which results in more consumption of energy. Therefore, through these conventional technologies, only a fraction of the energy of wastewater has been captured. In order to solve these issues, the next generation of municipal wastewater treatment plants is approaching total retrieval of the energy potential of water and nutrients, mostly nitrogen and phosphorus. These plants also play an important role in the removal and recovery of emerging pollutants and valuable products of different nature like heavy and radioactive metals, fertilizers hormones, and pharma compounds. Moreover, there are still few possibilities of improvement in wastewater treatment plants to retrieve and reuse of these compounds. There are several methods under development to convert the organic matter into bioenergy such as biohydrogen, biodiesel, bioethanol, and microbial fuel cell. These methods are capable to produce electricity from wastewater but still need an appropriate development. Energy development through wastewater is a great driver to regulate the wastewater energy because it produces 10 times more energy than chemical, thermal, and hydraulic forms. Vermicomposting can be utilized for stabilization of sludge from the wastewater treatment plant. Kesari and Jamal ( 2017 ) have reported the significant, economical, and ecofriendly role of the vermicomposting method for the conversion of solid waste materials into organic fertilizers as presented in Fig. 5 . Solid waste may come from several sources of municipal and industrial sludge, for example, textile industry, paper mill, sugarcane, pulp industry, dairy, and intensively housed livestock. These solid wastes or sewage sludges have been treated successfully by composting and/or vermicomposting (Contreras-Ramos et al., 2005 ; Elvira et al., 1998 ; Fraser-Quick, 2002 ; Ndegwa & Thompson, 2001 ; Sinha et al., 2010 ) Although collection of solid wastes materials from sewage or wastewater and further drying is one of the important concerns, processing of dried municipal sewage sludge (Contreras-Ramos et al., 2005 ) and management (Ayilara et al., 2020 ) for vermicomposting could be possible way of generating organic fertilizers for future research. Vermicomposting of household solid wastes, agriculture wastes, or pulp and sugarcane industry wastes shows greater potential as fertilizer for higher crop yielding (Bhatnagar et al., 2016 ; Kesari & Jamal, 2017 ). The higher amount of solid waste comes from agricultural land and instead of utilizing it, this biomass is processed by burning, which causes severe diseases (Kesari & Jamal, 2017 ). Figure 3 shows the proper utilization of solid waste after removal from wastewater; however, Fig. 5 showing greater possibility in fertilizer conversion which has also been discussed in detail elsewhere (Bhatnagar et al., 2016 ; Nagavallemma et al., 2006 )

figure 5

Energy production through wastewater (reproduced from Bhatnagar et al., 2016 ; Kesari & Jamal, 2017 )

9 Conclusions and future perspectives

In this paper, we have reviewed environmental and public health issues associated with the use of untreated wastewater in agriculture. We have focused on the current state of affairs concerning the wastewater treatment model and computational approach. Given the dire need for holistic approaches for cultivation, we proposed the ideas to tackle the issues related to wastewater treatment and the reuse potential of the treated water. Water resources are under threat because of the growing population. Increasing generation of wastewater (municipal, industrial, and agricultural) in developing countries especially in India and other Asian countries has the potential to serve as an alternative of freshwater resources for reuse in rice agriculture, provide appropriate treatment, and distribution measures are adopted. Wastewater treatment is one of the big challenges for many countries because increasing levels of undesired or unknown pollutants are very harmful to health as well as environment. Therefore, this review explores the ideas based on current and future research. Wastewater treatment includes very traditional methods by following primary, secondary, and tertiary treatment procedures, but the implementation of advanced techniques is always giving us a big possibility of good water quality. In this paper, we have proposed combined methods for the wastewater treatment, where the concept of the proposed model works on the various types of wastewater effluents. The proposed model not only useful for wastewater treatment but also for the utilization of solid wastes as fertilizer. An appropriate method for the treatment of wastewater and further utilization for drinking water is the main futuristic outcome. It is also highly recommendable to follow the standard methods and available guidelines provided WHO. In this paper, the proposed role of the computational model, i.e., artificial intelligence, fluid dynamics, and GIS, in wastewater treatment could be useful in future studies. In this review, health concerns associated with wastewater irrigation for farmers and irrigated crops consumers have been discussed.

The crisis of freshwater is one of the growing concerns in the twenty-first century. Globaly, about 330 km 3 of municipal wastewater is generated annually (Hernández-Sancho et al., 2015 ). This data provides a better understanding of why the reuse of treated wastewater is important to solve the issues of the water crisis. The use of treated wastewater (industrial or municipal wastewater or Seawater) for irrigation has a better future for the fulfillment of water demand. Currently, in developing countries, farmers are using wastewater directly for irrigation, which may cause several health issues for both farmers and consumers (crops or vegetables). Therefore, it is very imperative to implement standard and advanced methods for wastewater treatment. A local assessment of the environmental and health impacts of wastewater irrigation is required because most of the developed and developing countries are not using the proper guidelines. Therefore, it is highly required to establish concrete policies and practices to encourage safe water reuse to take advantage of all its potential benefits in agriculture and for farmers.

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Acknowledgements

All the authors are highly grateful to the authority of the respective departments and institutions for their support in doing this research. The author VT would like to thank Science & Engineering Research Board, New Delhi, India (Grant #ECR/2017/001809). The Author RS is thankful to the University Grants Commission for the National Fellowship (201819-NFO-2018-19-OBC-UTT-78476).

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Kavindra Kumar Kesari and Ramendra Soni contributed equally to this work.

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Department of Applied Physics, Aalto University, Espoo, Finland

Kavindra Kumar Kesari & Janne Ruokolainen

Department of Molecular and Cellular Engineering, Sam Higginbottom University of Agriculture, Technology and Sciences, Naini, Allahabad, India

Ramendra Soni, Jonathan A. Lal & Vijay Tripathi

Department of Health Informatics, College of Public Health and Health Informatics, Qassim University, Al Bukayriyah, Saudi Arabia

Qazi Mohammad Sajid Jamal

Department of Computational Biology and Bioinformatics, Sam Higginbottom University of Agriculture, Technology and Sciences, Naini, Allahabad, India

Pooja Tripathi

Department of Biotechnology, School of Engineering & Technology, Sharda University, Greater Noida, UP, India

Niraj Kumar Jha

Department of Bioengineering, Faculty of Engineering, Integral University, Lucknow, India

Mohammed Haris Siddiqui

Department of Forestry, NERIST, Nirjuli, Arunachal Pradesh, India

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Kesari, K.K., Soni, R., Jamal, Q.M.S. et al. Wastewater Treatment and Reuse: a Review of its Applications and Health Implications. Water Air Soil Pollut 232 , 208 (2021). https://doi.org/10.1007/s11270-021-05154-8

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Environmental Studies: Water Recycling

Introduction, works cited.

Water shortage is a situation where the available water cannot meet the demands of the population sufficiently. With the continued rise of the population and industrialization, there is much pressure on water sources to serve the growing needs of the people. The rise in demand for water has led to water scarcity due to high usage rates of this natural resource. But because water is a basic commodity for all organisms, the current water scarcity is at the moment one of the potential sources of conflict in the world today (Pereira et al., 20).

So far, humans have exhausted all the natural water sources available, including aquifers, yet most countries have not been able to develop methods of recycling water.

Effects of global warming have also led to a change in climate change leading to drought and hunger. Due to change in weather patterns, rivers and lakes have dried up leading to the water crisis, which has eventually created other problems since human depend on water for economic and domestic uses. Today, people are forced to move long distances in search of water, which is a basic commodity.

Water shortage has led to regional and community conflicts when people fight over control of the water sources leading to deaths and displacement of people from their areas of settlement. Ethnic fights, political interference, and conflicts in many parts of the world have led to the emergence of economic, social, psychological, and structural issues. Ethnic and religious tensions over depleting resources have been accompanied by competition and political conflicts between different communities (Filho, 14).

As such, governments have obligations to protect its population against any emerging issues that arise due to water shortage (Marsalek, 8).

It has been observed that water shortage contributes more problems than just drought and hunger; the government should, therefore, undertake strategies to address the same considering the great implication that water shortage can have in an economy (Weaver, 8). The government can help solve the issue of water shortage by creating awareness on water recycling, protecting existing water bodies, and doing desalination to have more clean water.

There is a need to solve the water shortage problem as a matter of urgency because of the following reasons. Firstly, water recycling will prevent the outbreak of water-related conflicts and deaths, which is usually caused by the struggle of water shortage (Weaver, 23). Secondly, constant food supply that is largely dependent on the water will be sustained, thereby eliminating hunger and starvation that leads to deaths and stagnation of economic progress of a country.

Thirdly, social problems associated with lack of water as well as psychological impacts can be solved by giving people access to potable water (Pereira et al., 43). It is the role of the government to make the economy of a country stable by making its population self-sufficient; water recycling ensures that the existing water sources are well protected. Finally, the government has a responsibility of protecting human rights that include access to clean and safe water as espoused in the MDG goals (Filho, 20).

Different countries face varying challenges in as far as the provision of clean water to its population is concerned depending on its economic development level and geographic location.

Notwithstanding this, any government must provide access to clean water to its citizens, and this is best achieved when awareness of water recycling is emphasized. It is thus the recommendation of this paper that water recycling is every government priority to ensure safe and clean water. Once access to clean water is achievable economic, social, and political stability will also be guaranteed.

Filho, Leah. The Economic, Social and Political Elements of Climate Change.  Berlin: Springer, 2010. Print.

Marsalek, Jiri. Urban water cycle processes and interactions . New York: Taylor and Francis, 2008. Print.

Pereira, Santos., Cordery, Ian., & Lacovides, Lacovos. Coping with Water Scarcity:  Addressing the Challenges . Berlin: Springer, 2009. Print.

Weaver, Alex. Exploring sustainability science: a southern African  perspective .Johanesburg: African Sun Media, 2008. Print.

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Good Water Recycling Essay Example

Type of paper: Essay

Topic: Water , Soil , Treatment , World , Recycling , Drinking , Alcoholism , Technology

Words: 2000

Published: 02/23/2020

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INTRODUCTION

Water recycling is a critical element for conservation of world’s water resource. Recycled water or reclaimed water is the wastewater, which is being treated to remove solids and certain impurities. This treated water is then used for extensive irrigation purposes, landscape irrigation, toilet flushing, industrial purposes and replenishing ground water. All water on Earth is recycled, but “recycled water” or “reclaimed water” means the wastewater, which is sent from homes and industries through pipelines to treatment plants. The process of treating wastewater or gray water is called Water Recycling. Sometimes recycled water is used to benefit ecosystem and improve aesthetics. On treating gray water, it is treated to meet the quality of water requirements for irrigation and other purposes. In other words, they are not treated enough to meet the quality standards for drinking water. Natural water cycle has facilitated water recycling on Earth for millions of years. Water recycling process may be characterized into two categories as planned or unplanned. One classic example of unplanned water recycling system is water from Colorado River and Mississippi river. Wastewater is collected upstream in these rivers and they undergo treatment several times, before the last downstream user withdraws water from pipelines. Planned water recycling projects are those that are designed with the specific goal to benefit through recycled water. Water harvesting is different from water recycling because, water harvesting involves simple methods like building storage tanks to collect rain and storm water. Whereas in water recycling, a complex mechanism is involved to ensure that, any hazardous material and highly degraded material are removed.

NATURAL WATER CYCLE

Natural water cycle has been the base for the evolution of water recycling technique. It is otherwise called as the hydrologic cycle or H2O cycle. This cycle describes the continuous movement of water on, above and below the surface of Earth. Many cities and countries recycle sewage water for irrigation and landscaping. However, they have been treated to the standards of drinking water, some of the communities are resistant towards use of recycled water. So indirect potable technique is widely used, since people feel more comfortable if river is a water source.

WORKING MECHANISM OF WATER RECYCLING SYSTEMS:

Water recycling treatment involves a series of water treatments in order to put them to use. Each level of treatment makes the water suitable for use for various purposes. However, recycled water is not used for drinking purposes. Following is the flow chart of a basic water recycling system. Indirect potable reuse is a system, which discharges water into a water body before reuse. Direct potable system discharges water for drinking directly after treatment. Direct potable system is generally not used in America but used safely in Namibia (Africa). The US Environmental Protection Agency regulated many aspects of drinking water quality and wastewater treatment. In 1992, EPA has released a technical document entitled “Guidelines for Water Reuse” which has information like summary of state requirements and guidelines for treatment and use of recycled water. Although most of the water recycling projects is designed to meet nonpotable water demands, there are some projects, which use recycled water for indirect potable uses. These projects involve recharging ground water aquifers and surface reservoir augmentations with recycled water. In ground water recharge projects, recycled water is used to inject into ground water aquifers and to augment ground water supplies and prevent intrusion of salt water in coastal areas. New technologies subject wastewater through three more stages namely: micro filtration, reverse osmosis and ultraviolet. By this way, impurities in the order of micron and nanometers can also be removed, thereby making it eligible for drinking water purpose. In future, if regulations are changed and recycled water proved to be purified to drinking water standards, they can be pumped directly into homes and industries.

ENVIRONMENTAL BENEFITS OF WATER RECYCLING

- Water recycling helps in decreasing diversion of fresh water from ecosystems - Decreases or eliminates discharge of wastewater into sensitive water bodies like lakes, estuaries or oceans. - Recycled water helps in enhancement or creating wetlands. - Water recycling can reduce and prevent pollution

DISADVANTAGES OF WATER RECYCLING

- Cost of recycling water is more, but still industries provide them at lower cost to promote the use of recycled water for nonpotable uses. - Perception of people regarding recycled water is negative. It is assumed that all recycled water is hazardous and dangerous to use, since its tagged nonpotable - One of the key disadvantages of recycled water is the health hazards it can cause due to the bacteria it may contain. Recycled water may contain E. coli or other bacteria, which can travel to wherever water is directed. On using for food irrigation, it can cause food-borne illness.

DIFFERENT WATER RECYCLING SYSTEMS

There are different ways to recycle wastewater. Recycling is possible in homes also. It should be noticed that, use of recycled water is illegal in some states like North Carolina. Even water from sinks and showers are considered as sewage water. Following are some of the simple and common methods for recycling water. - Waste Water Filtration System: This system uses a series of filters in a reservoir, to separate all solid and suspended matter in wastewater. They are most commonly used in association with rain barrel systems where sticks, leaves, stones, mud get collected. They can also be used in conjunction with sinks and showers, in order to monitor the use of this recycled water for purposes other than flushing toilets. - Unfiltered Waste Water Pump Systems: Unfiltered pump system is the most commonly used setup for water recycling in homes. This method cannot be used with rain barrels, because it may get clogged with sediments. It can be connected to bathroom sinks and showers, to reuse water in toilets and gardens. In this method, water enters a reservoir with a pump, which will send water to toilet. Suggested only if organic soaps are used. - Passive Grey water System: This is just a simple technique to reuse wastewater. If you carry a bucket to the shower, it will collect lot of water after bath. This collected water can then be used to flush toilet without any further treatments. - Custom Grey water Systems: As the name suggests, water-recycling system can be customized as per requirement. It can specify where wastewater goes and use it for irrigation at timed intervals. It can also monitor how much water is recycled. These are just a few examples of wastewater recycling techniques. A large variety of recycling systems are prevalent now.

ADVANCEMENTS IN WATER RECYCLING SYSTEMS

Large leaps have been taken in advancing water-recycling technologies. Recycling Water from Shower: In space, astronauts use same recycled water repeatedly throughout their course of time in space. This is possible with the use of water recycling as we shower. It works as a closed loop system. As water falls from the shower and goes into the drain, it is instantly purified to drinking water standards and again pumped back through the shower. Since water is hot already, it needs to get slightly heated. This system, which is used in space, can also be used on Earth. Membrane Separation System: This system offers the merits of space and energy savings, direct control of water purity, relatively low operating cost and no toxic chemical processing. This method is effective and efficient. It can recycle and purify water at considerably faster rates compared to conventional methods. Microfiltration: Here, water is purified through microfiltration technology, which can remove impurities up to 0.5 microns. It saves up to one fourth of the space occupied by a conventional water-recycling device. Reverse Osmosis: Reverse Osmosis or popularly known as RO is a widely used technique to purify water and use for drinking purposes. It detoxifies water and removes impurities up to 0.1 nanometers, which is not possible with other methods. Grey water recycling is still an undeveloped technology. Water treatment technologies in future may be developed to purify heavily contaminated water to suitable standards, but still its impact on environment will be high and justifiable on industrial scale.

WATER REUSE IN COLORADO

Reclaimed water has been used for landscape irrigation in Colorado in places like Colorado Springs and Aurora since 1950s and early 1960s respectively. Reuse has become common in cities like Colorado Springs, Aurora, Denver and Westminster. Reused water makes up about 40% of Las Vegas Valley water resource. Of the remaining water resource, the Colorado River provides 90% and groundwater provides 10%. Majority of water is used outdoors at residences.

Policy Regarding Recycled Water in Colorado:

- Expand return flow to Colorado River to increase Nevada’s credit for subsequent withdrawal. - Expand the use of recycle water in the Las Vegas Valley where large turf and industrial demands exist. - Maximize the use of Recycled Water in areas of Southern Nevada where return flow to the Colorado River System is not practical, including the testing of aquifer storage and recovery. - Develop a salt management strategy to address the accumulation of salts that are detrimental in Recycled water. - Continue to advance the research of the health and safety implications of Recycled water - Prohibit the use of treated or untreated Gray water in the Las Vegas Valley and prohibit its use outside the valley where there is reasonable potential for return flow to the Colorado River system or other Water Recycling programs. - Educate the public about our local water cycle and the benefits of Recycled Water. Denver Water supplies water for the city and country of Denver, Colorado and 70 suburban cities. As the largest water recycling facility of Colorado, treats up to 30 million gallons of effluent a day coming from the nearby metro waste water reclamation facility. This water is used for nonpotable demands. To supply drinking water, Denver Water treats water taken from South Platte River and Colorado’s Western slope of the Rockies. The water recycling plant diverts effluents from wastewater treatment plant, treats water from municipal sewage and industrial sources to a standard, which is safe to discharge into streams and rivers. For high-level treatment, water is tested for p H, turbidity, chlorine content and organics.

CONCLUSION:

Water recycling may not eliminate water scarcity across the world but it is definitely an effective solution for conservation of water for our future generations. In spite of the disadvantages of water recycling, its advantages takeover the necessity to develop this technique. Even if reused water cannot be put to use for drinking purposes, they serve a great deal as a source for non-potable utilities like cooling in industries, irrigation purposes, landscaping, betterment of ecological system, for recharging ground water aquifers, toilet flushing, etc., It is important to educate the public about the water recycling technique and remove the perception that, recycled water is hazardous.

- Guidelines for Water Reuse. US EPA Office of Technology Transfer and Regulatory Support. EPA/625/R-92/004. September 1992 - Municipal Wastewater Reuse: Selected Readings on Water Reuse. Office of Water (WH-595) EPA 430/09-91-002. September 199. - Layperson’s Guide to Water Recycling and Reuse, published in 1992 by the Water Education Foundation, Sacramento, California. - Water from Water: Recycling, produced in 1995 by National Water Research Institute, Fountain Valley, California. - Water in an Endless Loop, produced in 1997 by WateReuse Foundation, Sacramento, California. - http://www.epa.gov/region09/water/recycling/ - www.denverwater.org/recycle/project_overview.html - Water Recycling Comes of Age in Silicon Valley, audio report by Amy Standen for Quest Northern California on July 19, 2013. - http://greenliving.lovetoknow.com/Household_Waste_Water_Recycling_Systems - http://www.nasa.gov/home/hqnews/2004//HQ_04372_water_recycling.html

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Safety of recycled water for drinking Essay

Introduction, whether recycled water is safe for drinking.

Water recycling is the process by which individuals harness, treat and reuse water for various purposes. It may occur through water reclamation. This involves the treatment of sewage effluent for domestic and commercial use. Alternatively, recycled water may come from storm water or rain water.

Potable use is the human consumption of recycled water while planned reuse refers to deliberate treatment of wastewater for other uses. Recycled water holds a lot of promise in the field of agriculture and industry, but its application as a potable source is still quite contentious, limited and risky.

The question of whether recycled water is safe for drinking is of high relevance to a discussion on water-borne diseases because raw waste water contains high amounts of faecal matter, so it takes a rigorous and fool proof method to eradicate all disease-causing pathogens in recycled waste water.

Ashbolt (2004) explains that ingestion of unsafe drinking water transmits waterborne diseases. Usually, the water supply system of predisposed communities is susceptible to faecal contamination; over 1415 species of pathogens can be found in untreated waste water. Urine and faeces transmit these illnesses and may lead to severe complications or death. Typical examples include cholera, typhoid, gastroenteritis, infectious hepatitis, bacillary dysentery and amoeba, rotavirus, Escherichia Coli and Guardia Lamblia.

Treatment of waste water may minimise certain pathogens, but in highly infected water, it is difficult to eliminate all of them. Furthermore, recycling methods need to correspond to the development of new water-borne diseases. Scientists must also be aware of the genetic evolution of pathogens, which may make conventional treatment methods inadequate. Chemicals may also threaten public health if present in recycled water.

Conventional treatment may eliminate some chemicals, but could leave trace elements. Esposito et. al. (2005) affirm that the health effects of trace contaminants are still unclear at this point. Some organic compounds can disrupt hormonal systems even under extremely low concentrations. The international public health community is yet to create standards that would regulate treatment of waste water.

Therefore, parties must use a multi-thronged approach which would require elimination of all the threats at different levels (Steyn et. al. 2004). This is not just painstaking; it may cause excessive use of municipal and government resources. Toze (2006) explains that membrane filtration is one of the few effective routes of treating wastewater for portable use. However, it is quite expensive and takes a long time to complete. Jimenez and Chavez (2004) underscore the need for rigor in the treatment of wastewater for domestic purposes.

They assert that one must follow the fate of all the pollutants in the effluent in order to ascertain that they are absent. Esposito et. al. (2005) also outline some of the processes that waste water must go through during treatment. Disinfection and filtration systems in combination with secondary water treatment are effective for removing a portion of pathogens. The resulting product would only be sufficient for irrigation or non potable use.

On the other hand, ultrafiltration would minimise the risks associated with suspended particles. Sometimes certain pathogens are resistant to these processes. For instance, if one uses tertiary treatment on recycled water, one is likely to find viruses like cryptosporidium (Toze 2006). Elimination of chemicals is also essential in making recycled water safe for ingestion.

It would include the use of a series of treatments like nano-filtration, advanced oxidation as well as reverse osmosis. Ion exchange, biological degradation and chemical precipitation, are some synonyms of the above processes (Morud 2009). Owing to the complexity and diversity of disease-causing organisms and compounds in raw waste water, it is difficult to assure consumers of complete eradication of these pathogens in drinking water.

A number of advocates claim that recycled water is safe for drinking because water supply for key cities still comes from downstream rivers, which contain sewage effluent. However, using such a justification would be replacing one ill with another. It is one thing for cities to source their water from downstream rivers, with possible sewage contaminants.

On the other hand, when the concerned institution deliberately takes sewage effluent, then this increases the concentration of pathogens (DTI 14). It would increase the health risks of the population substantially when countries replace contaminated river water with sewage effluent.

Toze (2006) states that the concentration of pathogens in raw water supply highly affects the risks associated with treated waste water. If these sources have a high concentration of pathogens, health risks would increase. The author further states that treatment methods in current use leave certain pathogens in waste water. Cities such as New York are already investing so much in the cleanup of their water supply systems or estuaries (Esposito et. al. 2005).

Furthermore, public health officials suggest the placement of barriers as an effective method of protecting the masses form recycled water risks. One way would be preventing direct contact with contaminants. Therefore, it would almost retrogressive to use sewage effluent if it is already perceived as a health problem in many parts of the world.

Evidence from real-life cases is not sufficient to warrant consideration of recycled water for ingestion. Case studies on potable water reuse are few and hard to analyse. For instance, Anderson (2003) cites Orange County, in California, as one example. The county built a water reclamation plant that would treat water to drinking standard.

Not only did it employ a series of aquifers, but it also injected the water under high pressure. After fifteen years of intensive work, the recycled water was still not used for drinking. Po et. al. (2003) also talks about the controversies involved in portable reuse. For instance, Singapore worked on a project known as NEWater. The government wanted the project to curb dependence on other countries for water supply.

The Singaporean government even packaged the commodity in bottles such that the public could drink it conveniently. However, this plan did not work as few were willing to drink it. While the failure of the project failed due to public squeamishness towards the product, it still denied advocates of recycled water for potable use from having a tangible case study that could support their stand. Sometimes politics may come in the way of successful implementation of such projects.

Scientific backing may exist to support the safety of a water reclamation project. However, if lobbyists and other political groups undermine the implementation of the scheme, then one cannot study the immediate and long term effects of ingesting recycled water. As a result, it is not possible to make conclusive statements about the project. Namibia is a recurrent case study in water recycling analyses.

The city has been consuming recycled water from as far back as 1968. However, people rarely use recycled water directly in this country. Residents prefer blending the recycled water with conventional water. Sometimes the blend may be as high as 1:1 or may account for a quarter of the system in use (Anderson 2003). Direct portable reuse is not widespread because it requires transportation of recycled water from treatment plants into people’s homes.

The public and the scientific community are still not certain about the rigors of the treatment process. Therefore, many of them prefer to go for the indirect potable route (Marks et. al. 2006). If the pioneer of recycled water for potable use (Namibia) still cannot place all their confidence in reclaimed water, then one should question the plausibility of using the product for personal and human consumption.

Recycled water is not safe for drinking because of the health risks involved. Conventional treatment methods do not eliminate all microbes or chemical contaminants, and this could be dangerous. Additionally, few case studies exist to analyse the long term effect of 100% use (without blending) of recycled water among the masses.

Therefore, one cannot employ the method without support from conventional treatment systems. Finally, deliberate introduction of wastewater into water supply systems would increase the number of contaminants that require eradication, and this would pose a greater health risk than contaminated downstream water. Unless stakeholders eradicate these bottlenecks, then recycled water should not be treated as safe for drinking.

Anderson, J 2003 ‘The environmental benefits of water recycling and reuse’, Water Science and Technology , vol. 3 no. 4, pp. 1-10.

Ashbolt, N 2004 ‘Microbial contamination of drinking water and disease outcomes in developing regions’, Technology , vol. 198 no. 3, pp. 229-238.

DTI 200 ‘Water recycling and reuse in Singapore and Australia’, DTI Global Watch Mission Report , November, p. 1-79.

Esposito, K, Tsuchihashi, R, Anderson, J & Selstrom, J 2005, ‘The role of water reclamation in water resources management in the 21 st Century’, Water Environment , vol. 101 no. 4, 8621-8635.

Jimenez, B & Chavez, A 2004, ‘Quality assessment of potential use of an aquifer recharged with wastewater’, Water Science Technology , vol. 50 no. 2, pp. 269-76.

Marks, J, Martin, B & Zadoroznyi, M 2006, ‘Acceptance of water recycling in Australia: national baseline data’, Water , March, p. 152-159.

Morud, J 2009, Reclamation and reuse of wastewater , IUP, Iowa.

Po, M, Kaercher, D & Nancarrow, B 2003, ‘Literature review of factors influencing public perceptions of water reuse’, CSIRO Land and Water Technical Report , vol. 54 no. 3, pp. 1-33.

Steyn, M, Jagals, P & Genthe, B 2004, ‘Assessment of microbial infection risks posed by ingestion of water during domestic water use and full contact recreation in a mid southern African region’, Water Science and Technology , vol. 50 no. 1, pp. 301-308.

Toze, S 2006, ‘Water reuse and health risks-real vs. Perceived’, Desalination , vol. 187 no. 8, pp. 41-51.

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Essay on Recycling for Students and Children

500+ words essay on recycling.

Recycling is a method of procedure that includes the collection and breaking down of waste material to create something new out of it. The process was introduced sot that the non-biodegradable materials can be melted or break down to create something useful. After the effects of global warming and pollution have become known to men the process of recycling has become more important.

Essay on Recycling

Why We Need Recycling?

We need recycling for many reasons. But most importantly, it will help us to save our planet. Besides, recycling saves the earth by facilitating the reprocess of paper which will save millions of trees.

Also, recycling saves a lot of energy because many things that we recycle can easily be converted into virgin materials. In addition, it saves a lot of resources too.

Moreover, recycling reduces the burden of the environment. As we save energy the number of greenhouse gases and oxides are produced in less quantity. Because most of the toxic gases are produced by factories.

In addition, recycling reduces the amount of waste, that takes years to decompose. Also, the recycled material can be sold. We use this recycled material for the manufacturing of many new products. So, ultimately recycling saves money.

Get the huge list of more than 500 Essay Topics and Ideas

The Process of Recycling

The various materials that we recycle have to go through a process that refines and purifies them. Besides, different materials go through a different process and in this topic we will discuss the recycling process of various materials.

Paper- It is the most used material on the earth. Paper is made up of two materials water and wood. For recycling paper firstly they break it down in small pieces and dissolve it into water. After that, they add chemicals that filter out the ink and dirt from it. In addition after filtering the paper takes the form of a mush called the pulp and this pulp is later converted into clean paper.

Metals-  The metals are first shredded into small pieces and then they were melted and after that remolded into new shapes.

Glass- The recycling of glass is the easier they just break it into pieces and then they melt it and recast them.

Plastic- They also follow the same process as plastic. But, the process of plastic recycling is a little bit complex because they have to sort out the different types of plastics. As there is a diverse variety of plastic with different properties.

How Can We Contribute to Recycling?

Almost everything that we use can be recycled whether it is household materials like paper, plastic, metal, glass, furniture, toys, artifacts, vehicles, etc. Besides, opt for things from the market that can easily be recycled. Also, try to use merchandise that is made up of recycled products.

In addition, sort your waste and dump your recyclable waste in the recycle bin so that the authorities can recycle it.

To Sum it up, recycling is a small step by humans to save the environment . But this small step is very effective in the long run. Also, before throwing away the waste we should check it to see if there is a recyclable product in it or not.

FAQs about Essay on Recycling

Q.1 List some benefits of recycling. A.1 There are many benefits to recycling like:

  • It reduces the amount of waste produced by us.
  • Conserves natural resources such as water, wood, and minerals.
  • It prevents the overuse of resources and helps in preserving them.
  • In addition, it saves energy.

Q.2 Give an important fact related to recycling. A.2 An important fact can be that recycling reduces the amount of waste which goes to landfills. Also, lesser density in landfill means less amount of methane and other gases is released into the air.

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Water Conservation Essay in English for Students

Water is among the most crucial resources on Earth. However, humans are misusing it alarmingly. This article has some water conservation essays for raising awareness.

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October 19, 2023

Table of Contents

Water Conservation Essay: Water, essential for all life, is often overlooked as a finite resource. Water conservation is a shared responsibility to secure clean water for future generations. This blog covers the global water crisis, the importance of conservation, practical tips, successful projects, challenges, and the role individuals play.

Water Conservation Essay in English

Water represents one of life’s most fundamental elements, supporting the e500+ Words Essayxistence of all living organisms on Earth and serving as an indispensable resource for human survival. Despite the seeming abundance of water on our planet, the accessibility of clean, freshwater is a finite and restricted commodity. Thus, the preservation of water takes on paramount significance to guarantee that forthcoming generations can access this indispensable resource. In this article, we will explore the importance of water conservation and a variety of strategies to promote its prudent utilisation.

Water is an exhaustible resource, with Earth’s reserves of freshwater being limited. While approximately 70% of the Earth’s surface is enveloped in water, only a small portion of this constitutes freshwater, with a considerable fraction being locked away in glaciers and polar ice caps, rendering it inaccessible. The mounting global population and escalating water demands in agriculture, industry, and households have intensified concerns regarding the depletion of this valuable resource.

Among the most pressing concerns related to water conservation is the reckless and extravagant use of water in various parts of the world. Water wastage stems from issues like leaky faucets, continuously running toilets, and excessive irrigation practices. Addressing these issues necessitates the collaboration of individuals, communities, and governments to champion water conservation efforts.

Water conservation strategies are pivotal in securing the sustainability of our water supplies. The following are some effective approaches to conserve water:

  • Leak Rectification: Regularly inspect and rectify leaking faucets, pipes, and toilets to curtail water wastage.
  • Water-Efficient Appliances: Substituting outdated and inefficient appliances with water-efficient models like high-efficiency toilets, washing machines, and dishwashers, which consume significantly less water.
  • Rainwater Collection: Accumulating and storing rainwater for domestic and gardening use to alleviate the demand on local water reservoirs.
  • Xeriscaping: Opt for native and drought-resistant flora in landscaping to decrease the necessity for excessive watering.
  • Responsible Irrigation: Employ efficient irrigation techniques, such as drip irrigation, and schedule lawn and garden watering during cooler times to reduce water evaporation.
  • Curtail Shower and Bath Duration: Reducing shower and bath duration results in a considerable reduction in water consumption.
  • Faucet Management: Turn off taps when brushing teeth or washing dishes and employ basins for collecting water for rinsing vegetables or cleaning.
  • Educational Initiatives and Advocacy: Advocate for water conservation in your community and educate others about the importance of responsible water use.
  • Governmental Measures: Governments should enact and enforce water conservation regulations and provide incentives for individuals and businesses to save water.
  • Recycling and Reuse: Implement water recycling systems for industrial processes and utilise greywater for non-potable applications. Through the adoption of these practices, we can collectively wield a substantial influence on water conservation.

In summation, water conservation is not merely a choice; it is a necessity. The judicious and sustainable management of water is imperative to guarantee a continuous supply of clean and safe water for both the present and future generations. By implementing the aforementioned techniques for water conservation and fostering a culture of conscientious water use, we can collaborate to safeguard this invaluable resource and preserve the health of our planet.

Water Conservation Essay in 300 Words

Water conservation is a crucial endeavour in light of the finite nature of this life-sustaining resource. With the world’s population expanding and the demand for water rising across agriculture, industry, and households, responsible water use is imperative for future generations.

Minimising water wastage stands at the core of conservation efforts. Addressing issues like leaky faucets and pipes can result in significant savings. Moreover, the adoption of low-flow fixtures and appliances doesn’t compromise convenience while reducing consumption. Raising awareness and educational campaigns can promote these practices.

Efficient agricultural water management is pivotal. Techniques such as drip irrigation and precision farming minimise water wastage and enhance crop yields. Farmers can also embrace drought-resistant crops and rainwater harvesting for improved water efficiency.

Industries should prioritise water-saving technologies and recycling methods to reduce their water footprint. Government regulations and incentives can stimulate the adoption of sustainable water management practices.

Protecting natural water bodies like rivers, lakes, and wetlands is vital for ecosystem health. Pollution control and proper waste disposal are essential in safeguarding these sources. Preserving natural habitats plays a key role in maintaining water quality.

Community involvement is a potent driver of water conservation. Encouraging individuals to take responsibility for their water use and participate in local efforts can yield a significant impact on preservation.

In conclusion, water conservation is not a choice but a necessity. Responsible usage in homes, agriculture, and industry, combined with the safeguarding of natural water sources, ensures water’s availability for both current and future generations. This collective effort is indispensable for the survival of our planet.

Water Conservation Essay in 150 Words

Water stands as one of the most valuable resources on our planet, crucial for all life forms. Nevertheless, the availability of pure, freshwater is rapidly decreasing due to excessive use, contamination, and shifts in the climate. Hence, the preservation of water has emerged as a pressing global issue.

The act of conserving water is imperative to maintain ecosystems, support agriculture, and meet the rising needs of a continuously growing population. There exist several uncomplicated yet efficient methods to contribute to water conservation. Firstly, repairing leaks in pipelines and faucets can result in the preservation of numerous gallons of water annually. Secondly, employing low-flow fixtures and appliances aids in curtailing water consumption. Thirdly, cultivating mindfulness regarding water usage in daily routines, such as taking shorter showers and turning off the tap when not in use, can have a substantial impact.

In the realm of agriculture, implementing water-efficient techniques like drip irrigation can serve to conserve water. Industries have the potential to adopt recycling and wastewater treatment approaches to diminish water wastage.

Ultimately, it’s our collective responsibility to conserve water, as it ensures a sustainable future for ourselves and the generations to come. Water conservation is not just a choice; it’s a necessity.

Water Conservation and Management Essay

Water is Earth’s most precious resource, essential for all life, yet often overlooked. With a growing global population and escalating climate change, effective water conservation and management are critical. This essay discusses their importance, challenges, and strategies.

  • Scarce Resource: Freshwater is limited and under threat from pollution and overuse.
  • Ecosystems: Healthy aquatic systems maintain biodiversity and ecological balance.
  • Human Survival: Clean water is a fundamental human right.
  • Agriculture: Efficient water management in agriculture ensures food security.
  • Economic Stability: Water is integral to many industries.
  • Overuse and Wastage: Excessive consumption and wastage deplete resources.
  • Pollution: Chemicals, sewage, and industrial pollutants harm water sources.
  • Climate Change: Altered precipitation patterns make water management unpredictable.
  • Population Growth: Growing population strains resources.
  • Infrastructure: Many lack proper water infrastructure.
  • Education: Raise awareness about water conservation.
  • Technology: Develop water-saving solutions.
  • Infrastructure: Invest in water management infrastructure.
  • Legislation: Enforce water conservation and pollution control laws.
  • Ecosystems: Protect and restore natural habitats.
  • Recycling: Reuse treated wastewater.
  • Desalination: Sustainably harness desalination where needed.

In conclusion, water conservation and management are vital for our planet’s future, requiring education, technology, and responsible governance to address challenges and secure this invaluable resource. Act now to protect water for all.

Short Essay on Water Conservation

Water is an indispensable resource for life on Earth, but its supply is limited, necessitating urgent conservation. With global population growth, climate change, and increasing water demands in agriculture, industry, and households, preserving this resource is paramount.

Agriculture consumes about 70% of freshwater, making efficient irrigation methods and drought-resistant crops essential for conservation. Industries can reduce water usage through advanced recycling and treatment. At home, fixing leaks, using low-flow fixtures, and practising water-conscious habits make a big difference.

Government policies play a vital role through legislation, efficiency standards, and public awareness campaigns.

Water conservation is also tied to environmental preservation, as it prevents ecosystem disruption and reduces energy consumption and greenhouse gas emissions.

In conclusion, water conservation is a global imperative. It’s not just the responsibility of governments and industries but a shared duty of every individual. By acting now, we secure a sustainable future with abundant freshwater for generations to come.

Water Conservation Essay FAQs

Yes, many regions have regulations for water conservation, such as drought restrictions and efficient fixture requirements.

It ensures long-term water availability, essential for economic, social, and environmental sustainability.

Xeriscaping conserves water, lowers maintenance, and enhances aesthetics.

Yes, smart metres and data analytics enhance monitoring and efficiency in water conservation.

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Essay on Water Recycling | Techniques | Wastewater Management

essay on water recycling

Here is an essay on ‘Water Recycling’ for class 8, 9, 10, 11 and 12. Find paragraphs, long and short essays on ‘Water Recycling’ especially written for school and college students.

Essay # 1. Meaning of Water Recycling:

While recycling is a term generally applied to aluminum cans, glass bottles, and newspapers, water can be recycled as well. Water recycling is reusing treated wastewater for beneficial pur­poses such as agricultural and landscape irrigation, industrial processes, toilet flushing, and re­plenishing a ground water basin (referred to as ground water recharge).

Water is sometimes recycled and reused onsite; for example, when an industrial facility recycles water used for cooling processes. A common type of recycled water is water that has been re­claimed from municipal wastewater, or sewage. The term water recycling is generally used syn­onymously with water reclamation and water reuse.

Through the natural water cycle, the earth has recycled and reused water for millions of years. Water recycling, though, generally refers to projects that use technology to speed up these natural processes. Water recycling is often characterized as “unplanned” or “planned.”

A common exam­ple of unplanned water recycling occurs when cities draw their water supplies from rivers, such as the Colorado River and the Mississippi River, that receive wastewater discharges upstream from those cities. Water from these rivers has been reused, treated, and piped into the water supply a number of times before the last downstream user withdraws the water. Planned projects are those that are developed with the goal of beneficially reusing a recycled water supply.

American Water Works Association, 1999

Essay # 2. Benefits of Recycled Water:

Recycled water can satisfy most water demands, as long as it is adequately treated to ensure water quality appropriate for the use. In uses where there is a greater chance of human exposure to the water, more treatment is required. As for any water source that is not properly treated, health problems could arise from drinking or being exposed to recycled water if it contains disease-causing organ­isms or other contaminants.

The US Environmental Protection Agency regulates many aspects of wastewater treatment and drinking water quality, and the majority of states in the US have established criteria or guidelines for the beneficial use of recycled water.

In addition, in 2004, EPA developed a technical document entitled “Guidelines for Water Reuse,” which contains such information as a summary of state requirements, and guidelines for the treatment and uses of recycled water. State and Federal regu­latory oversight has successfully provided a framework to ensure the safety of the many water recycling projects that have been developed in the United States.

Recycled water is most commonly used for nonpotable (not for drinking) purposes, such as agriculture, landscape, public parks, and golf course irrigation. Other nonpotable applications include cooling water for power plants and oil refineries, industrial process water for such facili­ties as paper mills and carpet dyers, toilet flushing, dust control, construction activities, concrete mixing, and artificial lakes.

Although most water recycling projects have been developed to meet nonpotable water de­mands, a number of projects use recycled water indirectly for potable purposes. These projects include recharging ground water aquifers and augmenting surface water reservoirs with recycled water. In ground water recharge projects, recycled water can be spread or injected into ground water aquifers to augment ground water supplies, and to prevent salt water intrusion in coastal areas.

For example, since 1976, the Water Factory 21 Direct Injection Project, located in Orange County, California, has been injecting highly treated recycled water into the aquifer to prevent salt water intrusion, while augmenting the potable ground water supply.

While numerous successful ground water recharge projects have been operated for many years, planned augmentation of surface water reservoirs has been less common. However, there are some existing projects and others in the planning stages.

For example, since 1978, the upper Occoquan Sewage Authority has been discharging recycled water into a stream above Occoquan Reservoir, a potable water supply source for Fairfax County, Virginia. In San Diego, California, the Water Repurification Project is currently being planned to augment a drinking water reservoir with 20,000 acre-feet per year of advanced treated recycled water.

Essay # 3. Environmental Benefits of Water Recycling:

In addition to providing a dependable, locally-controlled water supply, water recycling pro­vides tremendous environmental benefits. By providing an additional source of water, water recycling can help us find ways to decrease the diversion of water from sensitive ecosystems. Other benefits include decreasing wastewater discharges and reducing and preventing pollution. Recycled water can also be used to create or enhance wetlands and riparian habitats.

a. Water Recycling Can Decrease Diversion of Freshwater from Sensitive Ecosystems:

Plants, wildlife, and fish depend on sufficient water flows to their habitats to live and reproduce. The lack of adequate flow, as a result of diversion for agricultural, urban, and industrial purposes, can cause deterioration of water quality and ecosystem health. Water users can supplement their demands by using recycled water, which can free considerable amounts of water for the environ­ment and increase flows to vital ecosystems.

b. Water Recycling Decreases Discharge to Sensitive Water Bodies:

In some cases, the impetus for water recycling comes not from a water supply need, but from a need to eliminate or decrease wastewater discharge to the ocean, an estuary, or a stream. For example, high volumes of treated wastewater discharged from the San Jose/Santa Clara Water Pollution Control Plant into the south San Francisco Bay threatened the area’s natural salt water marsh.

In response, a $140 million recycling project was completed in 1997. The South Bay Water Recycling Program has the capacity to provide 21 million gallons per day of recycled water for use in irriga­tion and industry. By avoiding the conversion of salt water marsh to brackish marsh, the habitat for two endangered species can be protected.

c. Recycled Water may be Used to Create or Enhance Wetlands and Riparian (Stream) Habitats:

Wetlands provide many benefits, which include wildlife and wildfowl habitat, water quality improvement, flood diminishment, and fisheries breeding grounds. For streams that have been impaired or dried from water diversion, water flow can be augmented with recycled water to sustain and improve the aquatic and wildlife habitat.

Water Recycling Can Reduce and Prevent Pollution-When pollutant discharges to oceans, rivers, and other water bodies are curtailed, the pollutant loadings to these bodies are decreased. Moreo­ver, in some cases, substances that can be pollutants when discharged to a body of water can be beneficially reused for irrigation.

For example, recycled water may contain higher levels of nutri­ents, such as nitrogen, than potable water. Application of recycled water for agricultural and landscape irrigation can provide an additional source of nutrients and lessen the need to apply synthetic fertilizers.

Essay # 4. Future of Water Recycling:

Water recycling has proven to be effective and successful in creating a new and reliable water supply, while not compromising public health. Non-potable reuse is a widely accepted practice that will continue to grow. However, in many parts of the United States, the uses of recycled water are expanding in order to accommodate the needs of the environment and growing water supply demands. Advances in wastewater treatment technology and health studies of indirect potable reuse have led many to predict that planned indirect potable reuse will soon become more common.

While water recycling is a sustainable approach and can be cost-effective in the long term, the treatment of wastewater for reuse and the installation of distribution systems can be initially expensive compared to such water supply alternatives as imported water or ground water. Insti­tutional barriers, as well as varying agency priorities, can make it difficult to implement water recycling projects. Finally, early in the planning process, agencies must implement public outreach to address any concerns and to keep the public involved in the planning process.

As water demands and environmental needs grow, water recycling will play a greater role in our overall water supply. By working together to overcome obstacles, water recycling, along with water conservation, can help us to conserve and sustainably manage our vital water resources.

Suggested Water Recycling Treatment and Uses'

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A glacier calving makes a huge splash.

Atlantic Ocean is headed for a tipping point − once melting glaciers shut down the Gulf Stream, we would see extreme climate change within decades, study shows

essay on water recycling

Postdoctoral Researcher in Climate Physics, Utrecht University

essay on water recycling

Professor of Physics, Utrecht University

essay on water recycling

Climate Model Specialist, Utrecht University

Disclosure statement

René van Westen receives funding from the European Research Council (ERC-AdG project 101055096, TAOC).

Henk A. Dijkstra receives funding from the European Research Council (ERC-AdG project 101055096, TAOC, PI: Dijkstra).

Michael Kliphuis does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

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Superstorms, abrupt climate shifts and New York City frozen in ice. That’s how the blockbuster Hollywood movie “ The Day After Tomorrow ” depicted an abrupt shutdown of the Atlantic Ocean’s circulation and the catastrophic consequences.

While Hollywood’s vision was over the top, the 2004 movie raised a serious question: If global warming shuts down the Atlantic Meridional Overturning Circulation, which is crucial for carrying heat from the tropics to the northern latitudes, how abrupt and severe would the climate changes be?

Twenty years after the movie’s release, we know a lot more about the Atlantic Ocean’s circulation. Instruments deployed in the ocean starting in 2004 show that the Atlantic Ocean circulation has observably slowed over the past two decades, possibly to its weakest state in almost a millennium . Studies also suggest that the circulation has reached a dangerous tipping point in the past that sent it into a precipitous, unstoppable decline, and that it could hit that tipping point again as the planet warms and glaciers and ice sheets melt.

In a new study using the latest generation of Earth’s climate models, we simulated the flow of fresh water until the ocean circulation reached that tipping point.

The results showed that the circulation could fully shut down within a century of hitting the tipping point, and that it’s headed in that direction. If that happened, average temperatures would drop by several degrees in North America, parts of Asia and Europe, and people would see severe and cascading consequences around the world.

We also discovered a physics-based early warning signal that can alert the world when the Atlantic Ocean circulation is nearing its tipping point.

The ocean’s conveyor belt

Ocean currents are driven by winds, tides and water density differences .

In the Atlantic Ocean circulation, the relatively warm and salty surface water near the equator flows toward Greenland. During its journey it crosses the Caribbean Sea, loops up into the Gulf of Mexico, and then flows along the U.S. East Coast before crossing the Atlantic.

Two illustrations show how the AMOC looks today and its weaker state in the future

This current, also known as the Gulf Stream, brings heat to Europe. As it flows northward and cools, the water mass becomes heavier. By the time it reaches Greenland, it starts to sink and flow southward. The sinking of water near Greenland pulls water from elsewhere in the Atlantic Ocean and the cycle repeats, like a conveyor belt .

Too much fresh water from melting glaciers and the Greenland ice sheet can dilute the saltiness of the water, preventing it from sinking, and weaken this ocean conveyor belt . A weaker conveyor belt transports less heat northward and also enables less heavy water to reach Greenland, which further weakens the conveyor belt’s strength. Once it reaches the tipping point , it shuts down quickly.

What happens to the climate at the tipping point?

The existence of a tipping point was first noticed in an overly simplified model of the Atlantic Ocean circulation in the early 1960s . Today’s more detailed climate models indicate a continued slowing of the conveyor belt’s strength under climate change. However, an abrupt shutdown of the Atlantic Ocean circulation appeared to be absent in these climate models.

This is where our study comes in. We performed an experiment with a detailed climate model to find the tipping point for an abrupt shutdown by slowly increasing the input of fresh water.

We found that once it reaches the tipping point, the conveyor belt shuts down within 100 years. The heat transport toward the north is strongly reduced, leading to abrupt climate shifts.

The result: Dangerous cold in the North

Regions that are influenced by the Gulf Stream receive substantially less heat when the circulation stops. This cools the North American and European continents by a few degrees.

The European climate is much more influenced by the Gulf Stream than other regions. In our experiment, that meant parts of the continent changed at more than 5 degrees Fahrenheit (3 degrees Celsius) per decade – far faster than today’s global warming of about 0.36 F (0.2 C) per decade. We found that parts of Norway would experience temperature drops of more than 36 F (20 C). On the other hand, regions in the Southern Hemisphere would warm by a few degrees.

Two maps show US and Europe both cooling by several degrees if the AMOC stops.

These temperature changes develop over about 100 years. That might seem like a long time, but on typical climate time scales, it is abrupt.

The conveyor belt shutting down would also affect sea level and precipitation patterns, which can push other ecosystems closer to their tipping points . For example, the Amazon rainforest is vulnerable to declining precipitation . If its forest ecosystem turned to grassland, the transition would release carbon to the atmosphere and result in the loss of a valuable carbon sink, further accelerating climate change.

The Atlantic circulation has slowed significantly in the distant past . During glacial periods when ice sheets that covered large parts of the planet were melting, the influx of fresh water slowed the Atlantic circulation, triggering huge climate fluctuations.

So, when will we see this tipping point?

The big question – when will the Atlantic circulation reach a tipping point – remains unanswered. Observations don’t go back far enough to provide a clear result. While a recent study suggested that the conveyor belt is rapidly approaching its tipping point , possibly within a few years, these statistical analyses made several assumptions that give rise to uncertainty.

Instead, we were able to develop a physics-based and observable early warning signal involving the salinity transport at the southern boundary of the Atlantic Ocean. Once a threshold is reached, the tipping point is likely to follow in one to four decades.

A line chart of circulation strength shows a quick drop-off after the amount of freshwater in the ocean hits a tipping point.

The climate impacts from our study underline the severity of such an abrupt conveyor belt collapse. The temperature, sea level and precipitation changes will severely affect society, and the climate shifts are unstoppable on human time scales.

It might seem counterintuitive to worry about extreme cold as the planet warms, but if the main Atlantic Ocean circulation shuts down from too much meltwater pouring in, that’s the risk ahead.

This article was updated on Feb. 11, 2024, to fix a typo: The experiment found temperatures in parts of Europe changed by more than 5 F per decade.

  • Climate change
  • Global warming
  • Extreme weather
  • Atlantic Ocean
  • Climate models
  • Greenland ice sheet
  • Ocean circulation

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The History of Moscow City

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