Reuse of Wastewater as Non-Conventional Water: A Way to Reduce Water Scarcity Crisis

Abstract

Water reuse is no longer a choice, it’s an essentiality. Sewage is considered as one of the stable and significant sources of alternative water. Limitation of water resources and fluctuations and climate changes, uneven distribution of water in the world, increasing population, pollution of surface and underground water, and reaching the stage of water stress in many countries made water managers and planners seek to use non-conventional sources of water to achieve sustainable development. Therefore, the use of wastewater as a reliable source of water in terms of quantity in various sectors, including agriculture and industry, has received serious attention. In line with the optimal management of water resources and achieving the desired situation and providing water needs in the future, measures such as demand management and increasing social awareness, supply management, prioritizing consumption, using returned water, increasing water productivity, etc., it is essential. One of the important solutions in this field is the recycling and reuse of wastewater, which leads to the reduction of surface and underground water consumption. The use of treated wastewater has many advantages, including a higher availability of water, sustainable utilization of water resources, reduced energy consumption, decreased nutrient loads, and increased production. It also promotes environmental protection and boosts employment and the local economy. The advantages of reusing wastewater will be discussed in this chapter.

1. Introduction

The problem of water scarcity is present due to both natural and man-made factors. Countries or regions around the world are currently experiencing chronic water shortages, which affect millions of people [1]. Severe water scarcity for at least 1 month each year is experienced by almost two thirds of the world’s population, comprising almost four billion people [2, 3]. Countries with inadequate water supply are home to over two billion people [4]. By 2025, water shortages could affect half of the world’s population [5]. By 2030, intense water shortage could result in the displacement of around 700 million people [6]. By 2040, it is estimated that one out of every four children worldwide will be living in areas with very high water stress [7]. Countries facing water crises should be concerned, as evidenced by the statistics [2]. When freshwater is used for domestic, sanitary, industrial, and service purposes, the remainder is disposed of as waste (wastewater) after consumption [8]. In numerous countries, wastewater is disposed of in natural watercourses, either as untreated or as treated effluent [9]. The investigators of the water and wastewater treatment industry think that natural resources, including freshwater, will remain under increasing pressure as a result of the growth of population for various uses, such as households and businesses [10]. The world is facing acute shortages of clean water and its population is affected by diseases associated with contaminated water due to the lack of a sustainable source of water [6]. With the intensification of the shortage of fresh and clean water in the world and with the increase in demand for water and due to drought conditions and climate changes, wastewater treatment has become one of the appropriate options to increase water sustainability [10]. Wastewater is the term used to describe water that has been polluted by humans. In other words, the remaining water after use in any of the domestic, industrial, commercial, or agricultural activities is called wastewater [11]. The used water from toilets, showers, baths, kitchen sinks, and laundries is known as home wastewater. Every day, the average amount of wastewater produced by domestic households is 200–300 L per person. The wastewater consists of 90% water and 10% contaminated waste [12]. The chemical contaminants in drinking water pose a threat to millions of people. These contaminants may be associated with naturally occurring inorganic chemicals such as arsenic and fluoride, which cause diseases such as cancer and tooth damage and/or skeletal damage, respectively [13]. Conversely, a wide range of severe health consequences may result from the inappropriate management of water supply in cities and industries or agricultural wastewater as well as prolonged exposure to them [13]. Therefore, this type of wastewater should often be directed to sewage treatment plants through collection pipes [10]. Taking early measures, including wastewater treatment, may help in reversing the catastrophic effects of living without clean and safe water for drinking, agriculture, or industrial use [10]. Industrial facilities also generate considerable amounts of wastewater that have chemicals or contents specific to their manufacturing process [14]. A source of wastewater, which comes from hospitals, offices, hotels, restaurants, airports, and many such areas, is called commercial wastewater that should be cleaned and made available for the next use [10]. The “fit-for-purpose” specifications for a specific next use are met by adequately treating these sources of water [15]. “Fit-for-purpose specifications” are the treatment requirements to bring water from a particular source to the quality needed, to ensure public health, environmental protection, or specific user needs [16]. For instance, the utilization of reclaimed water for agricultural purposes necessitates ensuring its quality is adequate to safeguard plants and soils, uphold food safety standards, and preserve the health of farm laborers [17]. When there is a higher level of human exposure to water, it may require more treatments. Direct potable wastewater reuse is an emerging water recycling technique that is still in its early stages of development. Untreated or contaminated water can transmit diseases, such as diarrhea, cholera, dysentery, typhoid, and polio and expose consumers to various public health challenges [18]. Grit, debris, suspended solids, pathogens that cause disease, decomposing organic waste, nutrients, and roughly 200 different chemicals have been identified as being present in wastewater [19]. The discharge of suspended solids, nutrients, organic chemicals, and metals into bodies of water is largely attributed to wastewater. The discharge of wastewater can result in various esthetic issues, including unpleasant odors and changes in coloration [19]. Disease-causing microorganisms, including bacteria and viruses, have the potential to render water unsuitable for both human and animal consumption [20]. The overabundance of nutrients can result in the excessive stimulation of aquatic vegetation growth. The decomposition of organic waste can deplete dissolved oxygen levels and pose a threat to the survival of aquatic organisms [21]. Aquatic organisms can be adversely affected by toxic chemicals, posing a threat to their well-being. Furthermore, excessive sedimentation can lead to the suffocation of fish’s feeding and spawning grounds [22]. Water recycling from wastewater, also known as reclaimed water, is a suggested approach to address the scarcity of water and combat drought conditions. This method involves the treatment and reuse of various types of wastewater, such as municipal, sanitary, and industrial wastewater. By implementing water recycling, we can effectively tackle the challenges posed by water shortages and ensure a sustainable water supply for various purposes [23]. Water recycling is underscored by several factors, including the scarcity of water supply, the absence of drinkable water, the presence of a substantial population, and its significance in safeguarding natural resources and the environment [23]. Water recycling involves the utilization of treated wastewater for beneficial applications, including agriculture, irrigation, and industrial processes [24]. Water recycling is a crucial component of effective water and wastewater management [23]. The utilization of contemporary techniques in wastewater treatment processes has led to remarkable advancements, thereby facilitating the widespread adoption of recycled water [23]. Nowadays, water treatment procedures have the capability to eliminate biodegradable compounds, essential nutrients, and harmful microorganisms from wastewater, resulting in purified water that can be utilized in various ways [9]. The primary objective of wastewater treatment is to segregate contaminants, eliminate suspended particles, eradicate toxins, and eradicate pathogens to enable the discharge of the resulting purified water, referred to as effluent, back into the environment for various applications [9, 10, 23]. Water recycling is a sustainable approach and is economical in the long run [25]. Water recycling offers numerous environmental benefits, including the reduction of wastewater discharge into the ecosystem and the mitigation of pollution. Moreover, it provides advantages in terms of water resource management [24]. Figure 1 shows wastewater reuse can be classified into several groups, including urban applications, industrial applications, agricultural applications, and groundwater recharge [8]. In this chapter, we will discuss the advantages of reusing the wastewater.

Figure 1.

Important applications of wastewater reuse: wastewater reuse can be classified into several groups, including urban applications, industrial applications, agricultural applications, groundwater recharge, and environmental restoration.

2. Benefits of wastewater treatment reuse in agriculture processes

2.1 Sustainable irrigation

For irrigation in agriculture, reuse of wastewater may be a reliable and sustainable source of water [26]. In particular in areas affected by water scarcity or drought, it will help farmers maintain crop yields and reduce reliance on freshwater resources [27]. Farmers are able to maintain agricultural productivity in the event of a scarcity or unavailability of freshwater, if they use untreated wastewater [28]. The need for freshwater resources is reduced when treated wastewater is diverted to agriculture. This makes a difference lighten the strain on conventional freshwater sources, such as streams, lakes, and groundwater, which are frequently overexploited or helpless to climate change-induced inconstancy in precipitation designs. The nutrient content of treated wastewater can benefit agricultural crops by providing essential macro- and micronutrients. In the case of proper treatment, wastewater may be an excellent source of nutrients for plant growth as well as a substitute to that which is used by industrial fertilizers. This may lead to improved soil fertility and crop yields, contributing to increased agricultural productivity [29]. Farmers can benefit economically from access to a reliable and consistent source of irrigation water through reuse of wastewater. It will reduce the need to utilize a costly freshwater water system and compensate for taking a toll on manure buys. In addition, the opportunities for farmers to participate in wastewater treatment and disposal could be created through wastewater reuse projects that would generate new income streams. Sustainable water management practices are promoted through the reuse of wastewater in agriculture [30]. Water resources can be preserved for essential needs, such as drinking water supply and ecosystem maintenance, through the use of treated wastewater instead of freshwater to irrigate. This will contribute to achieving a more efficient and effective use of water resources, thereby supporting the agricultural sector’s sustained resilience over time. By closing the loop in resource use, reuse of wastewater is compatible with the principle of a circular economy. Instead of treating wastewater as a waste product to be discharged, it is transformed into a valuable resource for agricultural irrigation. This promotes the recovery of resources, reduces waste, and contributes to a more sustainable and environmentally friendly approach to water and nutrient management [28, 29, 30]. Furthermore, reuse of wastewater is a significant solution to maintaining crop yields and the sustainability of agriculture, particularly for water scarcity regions, through provision of reliable and uniform sources of irrigation water, reducing pressure on freshwater resources, increasing farm productivity as well as promotion of responsible water management.

2.2 Nutrient-rich irrigation

Wastewater contains valuable nutrients, such as nitrogen, phosphorus, and potassium (NPK), which can be beneficial for growing plants. These nutrients may be used effectively in agriculture, reducing the need for fertilizers, through reuse of wastewater and encouraging healthy farming practices [8]. The reuse of wastewater allows for the recycling and recovery of nutrients in water, closing a nutrient cycle. Plants can use the nutrients contained in wastewater, such as nitrogen and phosphorus, to grow and develop [31]. This will reduce the need for synthetic fertilizers, which are energy intensive to produce, and may result in negative environmental impacts such as water pollution caused by nutrient discharges. The use of recycled water as an input source for nutrients can significantly reduce reliance on chemical fertilizers. Water pollution, eutrophication of water bodies, and the release of greenhouse gases (GHGs) can be caused by synthetic fertilizers that are not properly managed [10]. Reusing wastewater helps to reduce environmental risks by stopping nutrients from running off and decreasing the amount of harmful substances released into the environment. Treating wastewater properly makes the nutrients in it helpful for making soil more fertile [10, 30]. Plants need nitrogen, phosphorus, and potassium to grow. When these nutrients are present in wastewater, they can help the soil get more nutrients. This helps plants grow better and makes the soil healthier. This can make plants grow better, produce more crops, and create healthier farming areas [32]. By using wastewater that has nutrients in it, farmers can use less expensive fertilizers and save money. Using wastewater to provide nutrients to crops can help farmers save money and support a sustainable economy in farming [30]. Reusing wastewater on farms fits with sustainable farming, like organic and regenerative agriculture. It helps the environment by using wastewater in a smart way, instead of just throwing it away [10, 30]. Reusing wastewater in farming helps manage nutrients, reduces nutrient loss, and makes the environment healthier. Using cleaned wastewater for watering plants saves freshwater for important things. This is particularly relevant in regions that are suffering from water scarcity or where the availability of water resources is reduced [33]. The reuse of wastewater in agriculture promotes sustainable farming practices, reduces reliance on synthetic fertilizers, improves soil fertility, and supports environmental protection efforts by effectively exploiting the valuable nutrients contained in wastewater. It contributes to the sustainability and resilience of agriculture as a whole by providing an important source of nutrients for agricultural management.

2.3 Soil fertility improvement

Wastewater contains organic matter that can enhance soil fertility and structure [34]. The application of treated wastewater to agricultural lands can improve soil quality, leading to healthier and more productive crops. Wastewater contains organic compounds derived from human and industrial activities. When properly treated, these organic matter components can serve as an invaluable source of nutrients and improve the soil’s organic matter content [35]. Organic matter enhances soil fertility by increasing nutrient availability, promoting soil microbial activity, improving water-holding capacity, and enhancing soil structure. Treated wastewater contains a range of essential macro- and micronutrients, including nitrogen, phosphorus, potassium, and various micronutrients. These nutrients are critical for plant growth and are readily available for uptake by plants when wastewater is applied to agricultural lands. This nutrient provision can supplement or replace the use of synthetic fertilizers, reducing the reliance on chemical inputs and contributing to sustainable farming practices. The organic matter in wastewater helps improve soil structure by enhancing aggregation, water infiltration, and moisture retention. It contributes to the formation of stable soil aggregates, which improve soil porosity and aeration, root penetration, and nutrient exchange. Improved soil structure enhances root development, leading to healthier plants with increased access to soil nutrients and water. The organic matter present in wastewater acts as a food source for soil microorganisms, stimulating their growth and activity. Soil microorganisms play a crucial role in nutrient cycling, decomposition of organic matter, and the synthesis of compounds that enhance plant growth. The application of treated wastewater can promote a diverse and active soil microbial community, supporting nutrient availability and overall soil health. The presence of organic matter in wastewater can help prevent soil erosion by improving soil stability and increasing the binding capacity of soil particles [36]. Organic matter enhances the formation of soil aggregates that resist erosion caused by wind or water. Additionally, the improved water-holding capacity of soils due to organic matter can help retain moisture for longer periods, reducing irrigation needs and enhancing drought resilience. In rundown, by enriching soil organic matter, providing essential nutrients, improving soil structure, enhancing microbial activity, controlling erosion, and aiding in soil remediation, the application of adequately treated wastewater to agricultural lands promotes soil fertility and agricultural productivity. It supports sustainable farming practices, reduces reliance on synthetic inputs, and contributes to the overall resilience and long-term sustainability of agricultural systems.

2.4 Cost savings

Using treated wastewater for irrigation can help reduce the costs associated with purchasing and transporting chemical fertilizers and freshwater for irrigation [37]. This can be particularly beneficial for small-scale farmers or those operating in water-stressed regions, where accessing freshwater can be expensive. Treated wastewater contains valuable nutrients, including nitrogen, phosphorus, and potassium, which are essential for plant growth [37]. By utilizing treated wastewater for irrigation, farmers can reduce their reliance on chemical fertilizers. This, in turn, lowers the costs associated with purchasing and applying synthetic fertilizers, which can be a significant expense for farmers, especially in areas with high fertilizer prices. The use of treated wastewater as an irrigation source eliminates the need for purchasing freshwater for irrigation purposes. Accessing freshwater can be expensive, particularly in water-scarce regions or areas with limited infrastructure for water supply [37, 38]. By reusing treated wastewater, farmers can significantly reduce or even eliminate the costs associated with obtaining freshwater, directly impacting their operational expenses. Treating and supplying freshwater for irrigation often requires energy-intensive processes, such as pumping, purification, and distribution [39]. By opting for treated wastewater, farmers can save on the energy costs associated with these processes, contributing to overall cost savings. Additionally, treating wastewater can often be done locally, reducing the need for long-distance transportation and associated energy expenditures [40, 41]. Utilizing treated wastewater for irrigation can also help reduce the need for extensive infrastructure development for freshwater supply. Building irrigation infrastructure, such as pipelines, canals, or reservoirs, can be capital intensive and require ongoing maintenance [42]. By utilizing treated wastewater, farmers can leverage existing wastewater treatment infrastructure or establish decentralized treatment systems, reducing the need for additional infrastructure investments and minimizing maintenance costs. Water-stressed regions often experience higher freshwater costs during drought conditions due to increased demand and reduced supply [43]. By using treated wastewater for irrigation, farmers can reduce their vulnerability to drought and associated costs. Treated wastewater provides a reliable and consistent source of irrigation water, even during periods of water scarcity, ensuring crop productivity and reducing expenses that may arise from surging freshwater prices. In some cases, farmers may have the opportunity to generate revenue through wastewater reuse projects. By participating in the treatment and distribution of wastewater for agriculture, farmers can generate income through service fees or by selling surplus treated wastewater or treated wastewater byproducts. These additional revenue streams can offset agricultural production costs and contribute to farm sustainability [44]. In rundown, by reducing fertilizer expenses, eliminating freshwater costs, saving energy, cutting infrastructure expenses, improving drought resilience, and potentially generating additional revenue, the use of treated wastewater for irrigation provides substantial cost-saving benefits for farmers, particularly for small-scale farmers and those operating in water-stressed regions. It enhances economic viability, promotes sustainable farming practices, and contributes to the long-term sustainability of agricultural systems.

2.5 Reduced groundwater depletion

By reusing wastewater for irrigation, farmers can reduce their reliance on groundwater sources, which are often overexploited. This helps in preserving and managing groundwater resources more sustainably. Wastewater reuse allows farmers to use treated wastewater as an alternative water source for irrigation, reducing their reliance on groundwater [45]. Groundwater sources are often overexploited due to various factors, such as increasing agricultural demands, urbanization, and industrial activities. By using treated wastewater, farmers can significantly decrease their dependence on groundwater, relieving the pressure on these already stressed water sources. In some cases, treated wastewater can be used for groundwater recharge, replenishing depleted aquifers. This process involves intentionally injecting treated wastewater into the ground to replenish underground water reserves. Groundwater recharge helps restore groundwater levels and maintain their long-term sustainability [46]. By recharging groundwater with treated wastewater, farmers can actively contribute to the restoration and management of these vital water resources. Wastewater reuse for irrigation can reduce the risk of contamination and pollution of groundwater sources. When wastewater is not correctly treated or managed, it can contain harmful substances, pathogens, and pollutants that can leach into the soil and contaminate groundwater supplies [30]. By treating wastewater to high standards before reuse and implementing appropriate irrigation practices, the risk of groundwater pollution is minimized, ensuring the protection and long-term health of aquifers. Integrating wastewater reuse into agricultural practices supports a more sustainable water management approach. Instead of solely relying on dwindling groundwater resources, treated wastewater provides an additional and alternative water source for irrigation needs. This diversification of water supply helps balance water demands, reduces overreliance on a single resource, and promotes the efficient and sustainable use of water in agriculture [30, 33]. Climate change has brought about uncertain rainfall patterns, prolonged droughts, and water scarcity in many regions. By reusing wastewater, farmers can adapt to climate change impacts by having a reliable water source for irrigation, even during times of reduced rainfall or prolonged dry spells. This helps farmers maintain agricultural productivity and resilience in the face of climate-related challenges, ensuring the continuous growth of crops and food security [47]. In rundown, by reducing groundwater extraction, facilitating groundwater recharge, protecting aquifers from contamination, promoting sustainable water management, and aiding in climate change adaptation, wastewater reuse in agriculture plays a vital role in preserving and managing groundwater resources more sustainably. It supports long-term water security, reinforces agricultural sustainability, and contributes to the overall resilience of water systems in the face of growing water scarcity challenges.

2.6 Water conservation

Wastewater reuse in agriculture reduces the need for extracting freshwater from rivers, lakes, or underground sources. This conserves water resources and helps maintain environmental flow in water bodies, benefiting aquatic ecosystems and downstream users [30, 48]. By utilizing treated wastewater for irrigation, farmers can minimize the amount of freshwater they need to extract from natural sources. This reduction in water withdrawal helps to conserve water resources, ensuring that these sources remain available for other essential purposes, such as drinking water supply, industrial use, and maintaining healthy aquatic ecosystems. Environmental flow refers to the quantity, timing, and quality of water flows required to sustain aquatic ecosystems [35]. By reducing freshwater extraction for agriculture through wastewater reuse, more water is kept in the natural environment, allowing for the maintenance of adequate environmental flow. This is crucial for the health and biodiversity of rivers, lakes, wetlands, and other aquatic habitats, supporting the survival of various plant and animal species. Wastewater reuse practices in agriculture can alleviate pressure on freshwater ecosystems by decreasing the demand for water from natural sources. This helps in safeguarding the integrity of aquatic ecosystems and their associated habitats, allowing them to thrive in their natural state [30]. Furthermore, by reducing pollution and contaminants that might be present in the wastewater through proper treatment processes, the ecological health of water bodies can be improved, benefiting both aquatic species and downstream users. By reusing wastewater in agriculture, less water is withdrawn from freshwater sources upstream. This ensures that downstream users, such as communities, industries, and agriculture located further along the watercourse, have sufficient water available for their own needs [49]. By maintaining a sustainable water supply downstream, conflicts over water allocation can be minimized, supporting overall water resource management and promoting equitable distribution among different users. During drought conditions, when freshwater sources are scarce, wastewater reuse in agriculture becomes invaluable. By utilizing treated wastewater for irrigation, farmers can offset the reduced availability of freshwater, ensuring that agricultural activities continue even during these challenging periods. This helps maintain food production, farmer livelihoods, and overall regional stability [50, 51]. In rundown, by reducing freshwater extraction, preserving environmental flow, protecting and restoring aquatic ecosystems, sustaining downstream water availability, and mitigating the impact of droughts, wastewater reuse in agriculture plays a crucial role in conserving water resources and maintaining the ecological balance of water bodies. It supports the long-term sustainability of water systems, enhances water security for both human and environmental needs, and fosters resilience in the face of water scarcity and climate change challenges.

2.7 Diversification of water sources

When wastewater is reused in agriculture, it provides an additional source of water that can supplement traditional sources. This diversification helps reduce the vulnerability of agriculture to water scarcity and climate change impacts. As water scarcity becomes more prevalent due to factors like population growth, urbanization, and climate change, securing an adequate water supply for agriculture becomes increasingly challenging. Reusing wastewater provides farmers with an additional source of water that can supplement traditional freshwater sources. This diversification of water sources reduces the vulnerability of agriculture to water scarcity, ensuring a more consistent water supply, even during periods of reduced rainfall or water shortages. Climate change brings about increased uncertainty in rainfall patterns, temperature fluctuations, and extreme weather events. These impacts can disrupt agricultural activities and exacerbate water scarcity challenges. By incorporating wastewater reuse in agriculture, farmers can adapt to these climate change effects [27]. The availability of an alternative water source helps buffer the impacts of irregular rainfall, prolonged droughts, or changing hydrological patterns, enabling farmers to maintain agricultural productivity and resilience in the face of a changing climate. The integration of wastewater reuse in agricultural water management practices promotes a more efficient and sustainable use of water resources [10]. By utilizing treated wastewater for irrigation, farmers can optimize water allocation, ensuring that higher-quality freshwater sources are preserved for drinking water supply or other vital uses. This improved water management contributes to the long-term availability and sustainability of water resources, benefiting agriculture, communities, and ecosystems alike. Wastewater reuse offers farmers the opportunity to diversify their water supply sources [52]. By utilizing treated wastewater in conjunction with traditional freshwater sources, farmers reduce their dependence on a single water source. This diversification helps mitigate the risks associated with relying solely on freshwater, such as water scarcity, contamination, or price volatility. By harnessing multiple water sources, farmers can better manage water-related risks and adapt to changing conditions more effectively. Wastewater reuse supports sustainable agricultural practices and ensures food security. By providing an alternative water source, wastewater reuse enables farmers to sustain agricultural production and maintain crop yields, even when conventional water supplies are limited [28, 30]. This contributes to the overall stability and security of food systems, supporting local economies, farmer livelihoods, and food availability for communities, particularly in water-stressed regions. In rundown, by providing an additional water source, facilitating climate change adaptation, improving water management, promoting resource diversification, and ensuring sustainable agriculture and food security, wastewater reuse reduces the vulnerability of agriculture to water scarcity and climate change impacts. It strengthens the resilience of agricultural systems, enhances the ability to cope with water-related challenges, and supports the long-term sustainability of food production.

2.8 Local economic development

Wastewater reuse projects in agriculture can create employment opportunities and stimulate local economies. For example, the construction and operation of wastewater treatment facilities, as well as the distribution of treated wastewater to farmers, can generate jobs and boost economic growth [30]. Establishing wastewater treatment facilities requires skilled labor and expertise, creating employment opportunities during the construction phase. Engineers, technicians, construction workers, and other professionals are needed to design, build, and operate these facilities. This leads to the creation of jobs in the local economy, boosting employment rates and providing income opportunities for the workforce. Once wastewater treatment facilities are operational, ongoing maintenance and operation activities are necessary to ensure their efficient functioning [53]. This requires a workforce to monitor and maintain the infrastructure, perform regular inspections, conduct quality control checks, and manage the treatment processes. These operational roles offer employment opportunities and contribute to the local economy by providing stable jobs. Treated wastewater needs to be efficiently distributed to farmers for agricultural irrigation. This requires a network of distribution infrastructure, including pipelines, pumps, and storage facilities. The management and maintenance of this distribution system can create employment opportunities, such as technicians, operators, and logistics personnel responsible for ensuring the proper delivery and utilization of treated wastewater. Wastewater reuse projects often lead to the development of supporting industries and businesses. Local suppliers of materials, equipment, and services, such as pipelines, pumps, agricultural machinery, monitoring systems, and irrigation technologies, can benefit from increased demand and business opportunities. Additionally, businesses, such as wastewater testing laboratories, consultants specializing in wastewater management, and agricultural training and advisory services, can thrive, further contributing to the local economy [54]. Reusing wastewater in agriculture can stimulate the growth of agribusiness sectors by supporting increased crop production and diversification. Expanded agricultural activities driven by wastewater reuse can lead to the development of related industries, such as food processing, packaging, storage, transportation, and marketing. These value chains can create employment opportunities and generate economic growth, particularly in rural areas where agriculture is a primary source of livelihood. The economic benefits of wastewater reuse in agriculture extend beyond the immediate employment and business opportunities. The increased agricultural productivity resulting from reliable water supply stimulates the local economy through increased farm income, enhanced trade, and improved food security. The additional economic activity generated by wastewater reuse can have multiplier effects, supporting other sectors of the economy, such as tourism, hospitality, and retail, and contributing to overall regional development [55]. In rundown, by creating jobs in construction, operation, and maintenance activities, stimulating supporting industries and businesses, promoting agribusiness development, and generating multiplier effects, wastewater reuse projects in agriculture can have significant economic impacts. They contribute to local employment, income generation, and economic growth, fostering sustainable development and improving the livelihoods of communities involved in agriculture and wastewater management.

2.9 Climate change resilience

Wastewater reuse in agriculture can contribute to climate change adaptation by providing a more resilient water supply for irrigation. It helps farmers cope with variable and unpredictable weather patterns, reducing their vulnerability to droughts and other climate-related risks [51, 56]. By incorporating wastewater reuse in agriculture, farmers can diversify their water supply sources. This reduces their dependence on traditional freshwater sources, such as rivers or groundwater, which may become increasingly unreliable due to changes in precipitation patterns or reduced availability. The availability of an alternative water source through wastewater reuse helps farmers maintain a more consistent water supply, even during periods of drought or water scarcity caused by climate change. Climate change is leading to more frequent and intense droughts in many regions. Wastewater reuse provides an additional water source that can supplement conventional sources during periods of reduced rainfall or water scarcity [51]. By utilizing treated wastewater for irrigation, farmers can ensure a continuous water supply for their crops, mitigating the impacts of droughts on agricultural productivity and food security. Wastewater reuse often involves using treated wastewater for localized irrigation, targeting specific crops or areas with high water demand. This precision irrigation approach improves water use efficiency by delivering water directly to plant roots, minimizing losses due to evaporation, runoff, or overspray. With water scarcity becoming more prevalent under climate change, maximizing water use efficiency is vital for sustainable agriculture. Wastewater reuse helps farmers make the most of their available water resources, ensuring optimal use even under challenging climate conditions [57]. Wastewater contains valuable nutrients, including nitrogen, phosphorus, and potassium. When reused in agriculture, these nutrients can reduce the dependence on chemical fertilizers, contributing to sustainable and climate-smart farming practices. By using treated wastewater for irrigation, farmers can optimize nutrient management, promoting soil fertility and crop productivity. This nutrient recycling approach not only adapts to climate change but also reduces the environmental impact of fertilizers on water bodies and contributes to mitigating greenhouse gas emissions associated with fertilizer production. In areas prone to heat waves or rising temperatures due to climate change, wastewater reuse for irrigation can help regulate soil temperature and create a microclimate that is more favorable for plant growth. The application of treated wastewater can provide cooling effects, reducing heat stress on crops, and improving their resilience to extreme temperature events. Maintaining optimal soil moisture levels through wastewater reuse can also help buffer against temperature fluctuations, providing a more stable environment for plant growth. Implementing wastewater reuse in agriculture requires proper planning and infrastructure development. This process encourages farmers and communities to assess potential climate change risks, incorporate adaptation measures, and build resilience. By integrating wastewater reuse into their farm management practices, farmers adopt a proactive approach to climate change adaptation, reducing their vulnerability to climate-related risks and enhancing their long-term sustainability [38, 58]. In rundown, by diversifying water sources, ensuring water availability during droughts, improving water use efficiency, promoting nutrient recycling, providing temperature regulation benefits, and facilitating adaptation planning, wastewater reuse in agriculture contributes to climate change adaptation. It helps farmers cope with the impacts of climate change, reduces vulnerability to water-related risks, and promotes resilient agricultural systems that can withstand variable and unpredictable weather patterns.

3. Benefits of wastewater reuse in industrial processes

3.1 Water conservation

Reusing wastewater in industries helps save freshwater by using less of it [24, 59]. This is very important for industries that need a lot of water for their work, like manufacturing, producing energy, and mining. Companies can use wastewater again in their factories to use less freshwater. Instead of always getting lots of new water, they can clean and use the water they already have from their activities. This reduces the strain on local water resources, especially in areas which are stressed by drought or where there is a shortage [60]. By conserving freshwater resources, industries help sustainable management of water and prioritize its availability for other essential needs. Instead of putting wastewater into water bodies and ecosystem or sewage systems, industries can clean it and use it again in their work. This reduces the amount of liquid waste released, helping wastewater plants and lessening the harm that untreated or poorly treated wastewater can do to rivers and lakes [61]. By reducing the amount of wastewater they release, industries help keep water and aquatic life safe and healthy. Using recycled wastewater in industrial processes usually helps to use water more efficiently. Industrial companies can use new technology and methods to save water, using less water overall. This can mean making changes to how things are done, improving equipment, and finding ways to use less water [62]. By using water efficiently, industries can use less freshwater and help protect our water supply. Wastewater from factories can have useful stuff like energy, nutrients for plants, and metals, which can take it out and use it again [63]. The industry can obtain and recover these resources through wastewater treatment and reuse, thereby minimizing the need to extract or process new sources of materials. The circular economy principles, waste reduction, and the conservation of natural resources such as freshwater are promoted through this resource recovery approach. Reusing wastewater in factories can help the environment and save money [64]. Industries help the environment by saving water, keeping water clean, and cutting back on pollution related to using water. Regulatory requirements and sustainability objectives are often aligned with reuse of wastewater in industrial processes. In a lot of places, businesses have to use less water, put less water back into the environment, and find ways to use water again. By using wastewater again, industries can follow the rules and show they care about using water in a good way [65]. Finally, reuse of wastewater from industry plays a crucial role to preserve freshwater resources by reducing the consumption of freshwater, minimizing wastewater discharges, increasing water efficiency, promoting resource recovery, and achieving compliance with sustainability targets. It contributes to the sustainable management of water, supports ecosystems’ overall health, and ensures their availability for other essential purpose.

3.2 Cost savings

Reusing cleaned wastewater can save money on buying and treating freshwater for industrial use. The cost of water treatment and disposal is reduced, thus reducing reliance on expensive freshwater sources. Industries that rely on freshwater sources for their operations often incur considerable expenses associated with purchasing water [66]. The use of treated wastewater can decrease or remove the need for freshwater purchases, thus leading to savings in costs. It can be costly to treat freshwater in order to comply with the quality requirements of industrial processes. In order to be used for industrial applications, the water must go through a series of treatment processes including filtration, disinfection, and sometimes desalination [67]. Industries can save money by using treated wastewater, instead of treating a lot of freshwater. It may cost and be an environmental burden to dispose of wastewater produced by industrial processes. Getting rid of wastewater by putting it into rivers or sewage systems can cost money in charges, permits, and making sure you follow the rules. By using treated wastewater again, industries can decrease the amount of wastewater they have to get rid of, and save money on disposal. This can reduce the financial burden on wastewater treatment and disposal, thereby reducing costs. Energy savings for industry can also be achieved by the reuse of treated wastewater. Treated wastewater is already partly cleaned or filtered, so it takes less energy to treat it more compared to freshwater. Furthermore, water transport and distribution costs can be reduced due to the fact that untreated wastewater is able to originate from local sources, which eliminates the need for transporting freshwater in distant locations. In the case of industrial wastewater reuse, these energy savings contribute to overall cost reductions. As has been pointed out, there may be valuable resources like energy, nutrients, and metals in the wastewater. Industries have the possibility to recover and reuse those resources through wastewater treatment and recycling. This not only decreases the need for purchasing additional resources but also makes potential revenue streams from selling or utilizing the recovered resources. The revenue created from resource recovery can offset the costs related with wastewater treatment and fund to cost savings. In industrial plants, the reuse of wastewater can result in efficiency gains. The industrial sector can streamline its water management systems, optimize water use, and improve process efficiency through direct use of wastewater in a number of processes. This could lead to improvements in productivity, reduced delays, and increased operational efficiency, which would ultimately contribute to a reduction in costs over time [68]. In rundown, by decreasing freshwater purchase, minimizing water treatment costs, reducing disposal expenses, saving energy, generating revenue through resource recovery, and enhancing operational efficiency, reusing treated wastewater can significantly reduce costs for industries. These cost savings can enhance the economic viability of industrial operations and promote sustainable water management practices.

3.3 Enhanced efficiency

The overall efficiency of water use can be improved by using processed wastewater in industrial processes. Uninterrupted operation, minimizing interruptions and growing productivity, is ensured through the availability of a stable and reliable water supply [60]. Industries can ensure a stable and continuous supply of water to their operations with the use of recycled wastewater as an aquatic source. Treated wastewater may provide a stable water supply compared to the use of only changing freshwater resources. This stability will decrease the risk of interruptions in manufacture due to water scarcity or disruption, thus minimizing interruption and enhancing total operational efficiency. Industry can optimize their water management systems by implementing the reuse of treated wastewater. They are capable of designing and implementing processes to maximize the effectiveness of water use, reduce waste, and minimize overall water consumption. The adoption of water efficiency technologies, the implementation of closed-loop systems, and better management of water supply and storage practices are also part of this. In order to increase productivity and reduce water consumption, industry can make the most of available water resources by optimizing water reuse. In order to provide a more precise water application system, treated wastewater can be adapted for particular manufacturing processes. This precision enables the industry to supply water directly where it is required, minimizing losses by evaporation, leakage, or spraying. Industries can optimize their water use and reduction in the overall water consumption through the prevention of unwanted water loss. The efficient use of water resources will be ensured through this targeted approach in the application of water, leading to increased efficiency and productivity gains. Through closed-loop systems, treated wastewater may be recycled in industrial processes. In order to minimize the need for additional freshwater intake, water used in one part of the process may be treated and reused in another part of the process. This closed-loop method decreases the, in general, water request and improves water utilize effectiveness. The volume of water required for industrial operations can be substantially reduced through the implementation of closed-loop methods, increasing sustainability and minimizing water waste. Inspection, repair, and maintenance of water infrastructure and distribution systems are often involved in recycled wastewater reuse. Industries can detect and remedy water leakages via leaks and ineffective processes if they focus on the efficiency and integrity of their water supply systems. Loss and wastage of water are reduced through such an active approach to managing the water, resulting in improved efficiency as well as cost savings. Appropriate water management planning and monitoring is essential for the implementation of recycled wastewater treatment. In this way, industry can progress with their understanding of water consumption designs and identify areas for enhancement and implement water saving measures. Industry can improve water efficiency and ensure sustainable consumption through the optimization of water management practices, such as leak detection, metering, and real-time monitoring systems [69]. Finally, the use of untreated wastewater in industrial processes improves the overall water efficiency by improving the reliability and consistency of water supply, optimizing water reuse, enabling precise application of water, introducing close loop systems, limiting leakages, and managing water more effectively. This improved efficiency contributes to the sustainability and profitability of industry by ensuring uninterrupted operation, minimizing disruption, and increasing productivity.

3.4 Reduced environmental impact

Reusing wastewater mitigates the environmental impact associated with the discharge of untreated or partially treated wastewater into water bodies [70]. Treating and reusing wastewater helps in preserving water quality, preventing pollution, and protecting aquatic ecosystems. Untreated or inadequately treated wastewater discharge into water bodies can introduce pollutants, contaminants, and pathogens, negatively impacting water quality and aquatic ecosystems. By treating wastewater before reuse, industries remove or reduce harmful substances, such as organic matter, nutrients, heavy metals, and pathogens. This reduces the pollution load associated with wastewater discharge, preventing potential harm to water bodies and the organisms that depend on them. Discharging untreated wastewater can disturb the natural balance of aquatic ecosystems. High levels of nutrients, such as nitrogen and phosphorus from untreated wastewater, can lead to eutrophication, causing harmful algal blooms, oxygen depletion, and the degradation of aquatic habitats. By treating and reusing wastewater, industries minimize the release of excessive nutrients into water bodies, protecting the delicate balance of aquatic ecosystems and safeguarding the biodiversity they support. Wastewater reuse reduces the demand for freshwater sources, preserving these valuable resources for other essential needs. This is particularly important in areas facing water scarcity or regions where freshwater availability is limited. By reusing treated wastewater, industries decrease their reliance on freshwater extraction, preventing overexploitation of local water sources. Preserving water resources ensures long-term sustainability and supports the availability of water for diverse ecosystems, human consumption, and agriculture. Untreated or poorly treated wastewater can contain harmful pathogens, posing risks to public health through waterborne diseases. By treating wastewater before reuse, industries remove or inactivate pathogens, minimizing the potential for disease transmission. This protects public health, reduces the burden on healthcare systems, and ensures the safety of water sources used for various purposes, including drinking water supplies. Untreated wastewater may contain various chemicals, including industrial pollutants, pharmaceuticals, and personal care products. Discharging such wastewater into water bodies can result in chemical contamination, posing risks to aquatic organisms and potentially entering the food chain. Through proper treatment before reuse, industries can remove or reduce these chemical contaminants, preventing their negative effects on the environment and minimizing potential ecological and human health risks. Wastewater reuse aligns with regulatory requirements and sustainability goals related to water management and environmental protection. Many jurisdictions have strict regulations on the discharge of untreated or partially treated wastewater, encouraging industries to invest in wastewater treatment and reuse. By complying with these regulations and embracing wastewater reuse, industries demonstrate their commitment to sustainable practices and contribute to the overall protection of the environment [70]. In rundown, by treating and reusing wastewater, industries mitigate the environmental impact associated with untreated or partially treated wastewater discharge. They prevent water pollution, protect aquatic ecosystems, preserve water resources, prevent waterborne diseases, prevent chemical contamination, and comply with regulations and sustainability goals. Wastewater reuse is an essential component of sustainable water management, promoting environmental stewardship and contributing to a healthier and more sustainable planet.

3.5 Resource recovery

Wastewater contains valuable resources like energy, nutrients, and chemicals that can be recovered and reused in industrial processes. For example, the extraction of biogas from wastewater can generate renewable energy, and the recovery of nutrients can be used as inputs in fertilizer production or other industrial applications. Wastewater contains organic matter that can be converted into biogas through anaerobic digestion. Biogas, primarily composed of methane, can be captured and used as a renewable energy source for heating, electricity generation, or even as a vehicle fuel [64, 71]. The extraction of biogas from wastewater not only reduces the environmental impact of wastewater treatment but also contributes to energy independence and cost savings for industries. Wastewater is rich in nutrients like nitrogen and phosphorus, which are essential for plant growth. Instead of being discharged into water bodies, these nutrients can be extracted from wastewater and reused in agricultural fertilizer production. Recovered nutrients can also be utilized as inputs for hydroponic systems, aquaculture, or in the production of bioplastics, contributing to resource conservation and reducing the reliance on synthetic fertilizers. Wastewater can contain various chemicals and compounds that can be recovered and reused in industrial applications. For example, some industries can recover and reuse chemicals present in wastewater as inputs for their processes, reducing the need to purchase new chemicals. This not only results in cost savings but also reduces the reliance on virgin materials and minimizes the environmental impact associated with chemical production. Although water itself is not a resource recovered from wastewater, reusing treated wastewater can help preserve freshwater resources. By utilizing treated wastewater for non-potable purposes like irrigation, industrial processes, or toilet flushing, industries reduce their reliance on freshwater sources. This conservation of freshwater resources ensures their availability for other essential needs and minimizes the strain on water-stressed regions. Wastewater treatment processes often generate sludge or biosolids that can be further treated and reused. These biosolids can be converted into fertilizers or soil amendments, used in land reclamation projects, or employed in the production of biofuels. By recovering and reusing biosolids, industries can divert waste from landfills, reduce greenhouse gas emissions, and contribute to a circular economy approach [72]. In rundown, the recovery and reuse of resources from wastewater contribute to the transition toward a more sustainable and circular economy. It reduces the reliance on virgin resources, reduces waste generation and disposal, minimizes environmental impacts, and provides economic opportunities. By tapping into the valuable resources present in wastewater, industries can enhance resource efficiency, reduce costs, and support sustainable development.

3.6 Compliance with regulations

Wastewater reuse can help industries comply with stringent environmental regulations related to water usage and discharge. By reusing treated wastewater, industries can demonstrate their commitment to sustainability and environmental stewardship. Many regions face water scarcity or have limited access to freshwater sources. By reusing treated wastewater, industries reduce their reliance on freshwater extraction, thereby conserving water resources [73]. This aligns with environmental regulations that aim to promote responsible water management and ensure the sustainable use of water resources. Environmental regulations, such as effluent discharge limits, aim to protect water bodies from pollution. By treating wastewater before reuse, industries remove or significantly reduce pollutants, including organic matter, nutrients, heavy metals, and pathogens. This ensures that the discharged wastewater meets regulatory standards, preventing harmful impacts on receiving water bodies and reducing the risk of associated penalties or legal actions. Discharging untreated or partially treated wastewater can degrade water quality, affecting aquatic ecosystems and public health. By utilizing treated wastewater, industries contribute to maintaining high water quality standards. The advanced treatment processes applied to wastewater ensure that it is properly treated to remove contaminants and meet stringent regulatory requirements for various uses. By reusing treated wastewater, industries minimize the environmental impact associated with wastewater discharge. This includes reducing the introduction of pollutants and contaminants into water bodies, mitigating the risk of eutrophication, protecting aquatic ecosystems, and preserving biodiversity. By actively implementing wastewater reuse strategies, industries demonstrate their commitment to minimizing their environmental footprint and complying with regulatory standards. Environmental regulations often emphasize sustainable resource management and waste reduction. By recovering resources from wastewater, such as energy, nutrients, and chemicals, industries contribute to circular economy principles and sustainable practices. These resource recovery efforts align with regulatory goals related to waste reduction, resource conservation, and the promotion of a more sustainable industrial sector [74]. Wastewater reuse reflects a proactive approach to environmental management and corporate social responsibility. By implementing measures to reuse treated wastewater, industries demonstrate their commitment to sustainable practices, including reducing water consumption, conserving natural resources, and minimizing their impact on the environment. This proactive stance can enhance their reputation, build trust with stakeholders and the public, and attract environmentally conscious customers [73]. In rundown, wastewater reuse helps industries comply with stringent environmental regulations related to water usage and discharge. By conserving water, limiting pollutant discharge, protecting water quality, reducing environmental impacts, promoting sustainable resource management, and showcasing corporate responsibility, industries can meet regulatory requirements while contributing to a more sustainable future.

3.7 Community relations

Implementing wastewater reuse projects in industries can improve their public image and strengthen relationships with local communities and stakeholders [10]. It demonstrates a commitment to sustainable practices and responsible water management. By incorporating treated wastewater into their operations, industries showcase their dedication to conserving water resources and minimizing their impact on the environment [75]. This commitment resonates with stakeholders who value companies that prioritize sustainability and actively work toward reducing their ecological footprint. Reusing treated wastewater showcases industry’s role as an environmental steward. It highlights their proactive approach to minimizing the negative impacts of their operations on natural resources and ecosystems. This fosters goodwill among local communities, environmental groups, and other stakeholders who prioritize or advocate for environmental protection and sustainability. Conserving freshwater resources through wastewater reuse resonates with stakeholders concerned about water scarcity and the responsible use of water. By demonstrating a commitment to responsible water management, industries contribute to the preservation and sustainable use of water resources. This can help build trust and positive relationships with communities facing water scarcity or those who prioritize water conservation efforts. Implementing wastewater reuse projects provides an opportunity for industries to engage with local communities and stakeholders. Through open communication channels, industries can educate communities about their water management practices, the benefits of treated wastewater reuse, and the positive impact it has on local water resources. Engaging in community outreach initiatives and seeking input from stakeholders can foster positive relationships and enhance industry reputation as a responsible and accountable member of the community. Wastewater reuse aligns with regulatory requirements for responsible water management, thereby showcasing industry’s commitment to compliance. It demonstrates a proactive approach to meeting environmental standards and goes beyond mere compliance by actively contributing to sustainable water practices. This commitment to regulatory compliance and social responsibility enhances industry’s reputation and may result in increased support from regulators, government agencies, and community leaders. Embracing wastewater reuse can be appealing to environmentally conscious customers who prefer to support businesses that prioritize sustainability. By implementing sustainable water management practices, industries can position themselves as leaders in environmental responsibility and attract customers who prioritize environmentally friendly products and services. This can lead to increased market share and enhanced business opportunities [10]. In rundown, implementing wastewater reuse projects in industries improves their public image and strengthens relationships with local communities and stakeholders. It highlights industry’s commitment to sustainability, responsible water management, environmental stewardship, and community engagement. By actively demonstrating these values, industries can enhance their reputation, gain public support, and attract customers who prioritize sustainability and responsible business practices.

3.8 Innovation and technological advancements

The development and adoption of innovative technologies and solutions is encouraged by the reuse of wastewater in industrial processes. This will encourage research and development (R&D), enabling industries to explore new ways of optimizing water use, applying effective treatment processes, and improving efficiency in all aspects of operation. Industries invest in investigation and development to improve treatment technologies and production methods to make them more efficient, cost-effective, and capable of eliminating contaminants to meet stringent quality standards [10]. Innovative treatment processes are developing and being adopted to enhance operational sustainability as the industry focuses on optimizing water use. Advanced monitoring and control systems are being used by industry in order to guarantee the suitability and safety of reused wastewater. These systems use real-time sensors, data analysis, and automation to keep a constant monitoring of the water quality parameters as well as detecting any changes in treatment or control processes. Industry is able to maintain the required water quality and optimize its reuse process with the development and deployment of these technologies. Resources, such as nutrients, energy, and chemicals, are valuable and profitable in the wastewater. Technological progress has resulted in the development of processes allowing industries to recover this resource from wastewater. For example, nutrient extraction methods can detect and trap nutrients from wastewater for use in the manufacture of fertilizers or energy recovery systems can generate renewable energy from organic substance in wastewater [76]. The circular economy and the manufacture of additional value from wastewater are supported by investigation and deployment of resource recovery technology. The reuse of wastewater encourages industries to adopt water efficient processes and technologies during their operations. Industries innovate and optimize their manufacturing processes in order to minimize water requirements, with a view to decreasing the use of freshwater. In order to maximize water efficiency, it may include the introduction of closed-loop systems, water conservation equipment, and recycling technology. In order to optimize water resources and reduce their environmental footprint, these technologies are being developed and adopted by industry. Smart water management systems are frequently incorporated into the implementation of wastewater reuse projects. More accurate water management, reduction of water waste, and support for overall sustainability efforts can be achieved through the integration of smart technologies in industrial processes. Collaboration between different stakeholders, such as investigators, engineers, and industry experts, is encouraged when implementing wastewater reuse plans. By making it easier to exchange ideas, experiences, and best practices, knowledge sharing and collaboration is promoting innovation. This collective approach is helping in the growth and progress of technologies and solutions for wastewater reuse, which will improve environmental sustainability in industrial processes [77]. Overall, the reuse of wastewater in industrial processes is stimulating innovation and technological progress in water treatment, resource recovery, water efficiency, and smart water use. These advances are improving the sustainability of operations, increasing water quality monitoring, and contributing to the development of a circular economy. The industries benefit from these innovations, ensuring the appropriate and effective use of water resources while mitigating their impacts on the environment.

4. Benefits of wastewater reuse in groundwater replenishment processes

4.1 Groundwater recharge

The reuse of treated wastewater in groundwater replenishment processes involves injecting it into the aquifers and replenishing water reserves [46, 78]. It also aids to restore depleted aquifers and maintain sustainable groundwater levels. High-quality treated water is pumped into the subterranean aquifers to replenish groundwater [79]. Before injecting it into the ground, the wastewater goes through a thorough cleaning process to take out any harmful stuff like germs and chemicals [80]. It shall ensure that the injected water complies with suitable water quality standards. The depletion of groundwater reserves is restored through the injection of treated wastewater to underground aquifers. Over time, the injection water will mix with groundwater already in place and increase its total amount of water within the aquifer. It contributes to the restoration of groundwater levels in aquifers that were previously drained, thereby making them more resilient and able to cope with water needs for years to come. Using treated wastewater to refill the groundwater helps to keep a steady supply of water balanced with the demand for it. In places where people use a lot of groundwater, taking too much water can cause the groundwater to run out. The water supply is enhanced and the reliance on unsustainably high pumping rates from subterranean sources has been reduced by using treated wastewater to fill aquifers. This will render assistance to decrease the risk of overextraction and promote sustainable groundwater supplies for a long time. Injecting treated wastewater into aquifers for groundwater replenishment can help develop water quality. The injected water undergoes additional treatment by biological, physical, and chemical processes, as it is naturally filtered through the surrounding soil and rock layers [80]. This may result in further elimination of trace contaminants and show progress with the overall water quality when it is used to recharge an aquifer [81]. In coastal areas, the excessive extraction of groundwater can result in seawater intrusion where saline water infiltrates freshwater aquifers [81]. By refilling underground water sources with cleaned wastewater, we can reduce the strain on freshwater supplies and lower the chances of saltwater getting into them. This will help maintain the integrity of groundwater aquifers and ensure a sustainable supply of water which is naturally filtered. The groundwater resources face important challenges due to climate change, which includes long droughts and water scarcity. Using treated wastewater to refill groundwater can help us deal with changing conditions in a way that lasts a long time. During periods of high rainfall or surplus water, regions can effectively store excess water by injecting treated wastewater into aquifers, creating a buffer against future droughts, and ensuring long-term water security [82]. Overall, using treated wastewater to recharge groundwater is a good way to fill up aquifers and manage groundwater in a sustainable way. It’s helping to ensure water supply demand is balanced, preventing saltwater intrusion, improving water quality, and adapting to the challenges of climate change. Communities can ensure the long-term availability and sustainability of their groundwater sources through this approach.

4.2 Water resource sustainability

Groundwater is a vital source of freshwater for many communities around the world [83]. By recharging groundwater with treated wastewater, the long-term sustainability of this valuable water resource can be ensured, reducing reliance on surface water or unsustainable extraction practices [83]. By recharging groundwater with treated wastewater, communities can diversify their water sources [83]. This reduces their reliance on surface water bodies such as rivers and lakes, which are often subject to seasonal variations in availability and quality. Groundwater replenishment through wastewater reuse provides an additional, reliable source of freshwater, helping to secure water supply, even during periods of drought or surface water scarcity [82]. Recharging groundwater with treated wastewater reduces the demand for surface water resources. This is particularly important in regions where surface water bodies are already overexploited. By relying on treated wastewater, communities can reduce the pressure on surface water sources, ensuring their long-term sustainability and minimizing the risk of their depletion. Groundwater replenishment through wastewater reuse enhances water security by reducing dependence on external water supplies. It provides a locally available and controlled water source, reducing vulnerability to disruptions in surface water availability (e.g., droughts and pollution) or limitations in water transfer infrastructure. Communities can rely on the recharged groundwater as a consistent and secure resource for their water needs, reducing the risk of water shortages and ensuring stability and resilience in the face of changing conditions. Recharging groundwater with treated wastewater helps to sustainably manage and protect aquifers [84]. Instead of relying solely on groundwater extraction, which can lead to depletion and related problems like land subsidence, communities can utilize treated wastewater to replenish aquifers and maintain sustainable groundwater levels. This approach promotes responsible water management, preserving the long-term viability of groundwater resources for future generations. Treated wastewater used for groundwater replenishment goes through rigorous treatment processes to meet quality standards before injection. This improves the overall quality of the recharged groundwater. By replenishing aquifers with high-quality water, the treated wastewater helps to improve groundwater quality and reduces the need for extensive treatment when the water is later extracted for human consumption or industrial use [85]. Groundwater replenishment through treated wastewater reuse can be a cost-effective and energy-efficient approach to meet water demands. Compared to constructing and maintaining extensive infrastructure for water transfer or desalination, using treated wastewater for groundwater recharge can be economically advantageous. It also reduces energy requirements, as it avoids the need for energy-intensive desalination processes or long-distance water transportation [85]. In rundown, recharging groundwater with treated wastewater provides a sustainable solution to promote the long-term sustainability of this valuable freshwater resource. It reduces reliance on surface water or unsustainable extraction practices, enhances water security, and conserves surface water resources. By utilizing this approach, communities can ensure a reliable and locally controlled water source while preserving and maintaining the integrity of their groundwater reserves.

4.3 Water quality improvement

Treated wastewater used for groundwater replenishment goes through an advanced treatment process, removing contaminants and pollutants. This improves the overall quality of the injected water, ensuring that the replenished groundwater remains clean and safe for use. The treatment process begins with primary treatment, where physical processes such as screening and sedimentation are used to remove large solids, debris, and settleable particles from the wastewater [86]. This initial step helps prevent clogging in subsequent treatment processes and protects downstream equipment. After primary treatment, the wastewater undergoes secondary treatment, which focuses on the biological removal of organic matter and the reduction of nutrients [87]. This typically involves biological processes like activated sludge, trickling filters, or rotating biological contactors. Microorganisms break down organic pollutants, converting them into solids that settle or form flocs. Tertiary treatment is the advanced stage of the treatment process, specifically designed to remove remaining contaminants and pollutants [88]. Various techniques are employed, depending on the specific requirements and the level of water quality desired. Common tertiary treatment processes include filtration, advanced oxidation, membrane filtration (e.g., microfiltration, ultrafiltration, and reverse osmosis), disinfection (e.g., chlorination and ultraviolet (UV) disinfection), and nutrient removal (e.g., denitrification and phosphorus removal). Advanced filtration processes like microfiltration, ultrafiltration, and reverse osmosis play a crucial role in removing even smaller particles, suspended solids, dissolved organic matter, and trace contaminants from the treated wastewater [88]. These processes utilize membranes with fine pores that selectively filter out contaminants based on their size and molecular properties, producing high-quality water. To ensure the safety of the injected water, disinfection is typically performed as the final step of the treatment process. Common disinfection methods include chlorination, UV disinfection, and advanced oxidation processes. These methods target and destroy or deactivate any remaining pathogens, bacteria, viruses, or other harmful microorganisms that may be present in the treated wastewater [89]. It’s important to note that the specific treatment processes and technologies may vary depending on local regulations, water quality goals, and the intended use of the replenished groundwater. However, the overarching aim of the treatment process is to ensure that the treated wastewater meets stringent quality standards, guaranteeing the cleanliness and safety of the injected water for the long-term sustainability of groundwater resources [86]. In rundown, by undergoing these advanced treatment processes, the treated wastewater for groundwater replenishment is effectively purified, with contaminants, pollutants, and pathogens removed or greatly reduced. This ensures that the injected water is of high quality and meets appropriate water quality standards. The improvement in water quality safeguards the replenished groundwater, providing clean and safe water for various uses such as irrigation, industrial processes, or even drinking water supply (with additional treatment, if necessary).

4.4 Drought resilience

In times of drought or water scarcity, groundwater replenishment through reuse of wastewater helps to make a buffer [90]. By renewing aquifers, communities can depend on put-away groundwater amid dry periods, diminishing the defenselessness to drought-induced water deficiencies. Groundwater replenishment provides a means of storing excess water during periods of high rainfall or surplus water availability. By infusing treated wastewater into aquifers amid these times, communities can successfully store water underground. In the event of limited or reduced surface water supply, such storage water shall act as a buffer and provide an adequate source of water for subsequent dry periods. Ensuring a sustainable supply of water is also helping communities become more resilient to droughts, in spite of the diminished availability of surface waters. The groundwater storage capacity is increased when the aquifers are replenished with treatment water [85]. Amid times of tall water accessibility, overabundance of water can be infused into the aquifer, successfully reviving it. This helps in the growth of the volume of water stored underground, making a reserve that can be tapped into during droughts. The better the replenishment efforts, the larger the amount of water available in the aquifer, providing a longer-term buffer against water scarcity. Groundwater, when legitimately overseen and revived, offers a consistent and true and reliable water supply amid dry seasons. Not at all like surface water sources that can be intensely affected by varieties in precipitation or drying up amid drawn-out dry spells, renewed groundwater encompasses a slower exhaustion rate. This enables more sustainable and reliable water sources to be relied upon in communities. Groundwater replenishment through wastewater reuse helps decrease vulnerability to water use restrictions. Amid dry spells, water shortage can lead to strict controls and restrictions on water utilization, especially from surface water sources. Communities can reduce their reliance on surface water and, at the same time, avoid or minimize the impact of these restrictions through the use of recharged groundwater. In addition, groundwater replenishment supports local water management and reduces reliance on external water sources. Communities are empowered to manage and control their water resources through the use of treated wastewater within the same catchment area or region. This will reduce the vulnerability of regions to outside factors, such as water transfers, or reliance on distant sources that may be more vulnerable to drought caused shortages. Groundwater replenishment is a long-term solution to ensure water security, in particular in areas with a history of drought and water scarcity [91, 92]. By infusing treated wastewater into aquifers amid damp periods, communities can construct up-saves that can be withdrawn amid times of low precipitation or constrained surface water availability. In the face of climate change, such sustainable practices support to preserve a stable and secure water supply [93]. Overall, when times of drought or water scarcity occur, groundwater replenishment by the reuse of wastewater helps to create a buffer against this. This will increase the storage capacity of aquifers, provide a reliable water supply, reduce vulnerability to water use restrictions, support regional water management, and ensure sustainable water security in the future. The use of this approach allows communities to better manage and cope with drought conditions, mitigate their impact on water scarcity, and ensure a sustainable water supply in the future.

4.5 Reduced wastewater discharge

By reusing wastewater for groundwater replenishment, the discharge of treated wastewater into surface water bodies is reduced [24]. This leads to a decrease in the pollution and ecological impacts associated with the direct release of treated wastewater into rivers or oceans. Reusing treated wastewater for groundwater replenishment eliminates or greatly reduces the direct discharge of treated wastewater into rivers, lakes, or oceans. This prevents the pollution of surface water bodies with potentially harmful substances, pollutants, and nutrients that may still be present in treated wastewater. By diverting treated wastewater to recharge aquifers, the risk of contaminating surface water, harming aquatic ecosystems, and compromising water quality downstream is mitigated [94]. Discharging treated wastewater directly into water bodies can have detrimental impacts on aquatic ecosystems. High nutrient levels, such as nitrogen and phosphorus, can cause eutrophication, leading to oxygen depletion and the formation of harmful algal blooms. These episodes can harm fish populations, degrade water quality, and disrupt the balance of aquatic ecosystems. By diverting treated wastewater for groundwater replenishment, these negative impacts on surface water ecosystems are minimized, preserving the health and biodiversity of these environments. When wastewater treatment plants release treated wastewater into rivers or oceans, there is still the potential for downstream pollution as the water flows through different regions. By reusing wastewater for groundwater replenishment, the risk of downstream pollution is significantly reduced. The treated wastewater is injected into the ground, effectively removing the potential for contamination and pollution downstream, where it could impact other communities, water users, and sensitive ecosystems. In coastal areas, the discharge of treated wastewater into the ocean can harm delicate marine environments, including coral reefs, seagrass beds, and coastal habitats. Nutrient enrichment, increased turbidity, and the introduction of contaminants in treated wastewater can disrupt these ecosystems, affecting marine life and biodiversity. By recharging groundwater with treated wastewater, the discharge into coastal waters is reduced, minimizing the ecological impacts on these valuable ecosystems [95]. Surface water bodies often serve as sources of drinking water for communities. The direct discharge of treated wastewater into these water bodies can introduce contaminants and pollutants that may pose risks to public health and require extensive additional treatment for their removal. By reusing wastewater for groundwater replenishment, the potential for contamination of drinking water sources is reduced [24]. Treated wastewater undergoes advanced treatment processes to meet stringent quality standards before being injected into aquifers, ensuring the protection of groundwater resources that may be tapped for drinking water supply. Reusing wastewater for groundwater replenishment is an integral part of the circular water management approach, where water is treated, reused, and recycled in a sustainable manner. By closing the loop and reusing treated wastewater, the valuable water resource is conserved, significantly reducing the reliance on freshwater extraction and the need for additional water supplies, thus contributing to a more sustainable and resilient water management system [96]. In rundown, reusing wastewater for groundwater replenishment helps decrease the discharge of treated wastewater into surface water bodies, reducing pollution and ecological impacts. It protects surface water quality, preserves aquatic ecosystems, prevents downstream pollution, safeguards coastal environments, protects drinking water sources, and promotes circular water management. This sustainable practice contributes to the overall health and sustainability of water resources, benefiting both human and ecological communities.

4.6 Potable water supply augmentation

Groundwater replenishment processes, when coupled with advanced treatment technologies, can produce high-quality water suitable for potable water supply [97]. This increases the overall freshwater supply and diversifies sources, reducing the reliance on traditional water sources and minimizing the need for costly infrastructure projects. Groundwater replenishment typically involves the use of advanced treatment technologies, such as membrane filtration, reverse osmosis, UV disinfection, and advanced oxidation processes (AOPs) [98, 99, 100]. These processes are capable of removing a wide range of contaminants, such as suspended solids, pathogens, nutrients, salts, and trace organic compounds. The combination of multiple treatment barriers ensures that the treated water meets stringent water quality standards and can be safely used for various purposes, including potable water supply. The incorporation of advanced treatment technologies enables the production of high-quality water that meets or surpasses regulatory standards for drinking water. Through robust treatment processes and multiple safeguards, including rigorous monitoring and quality control measures, the final product from groundwater replenishment can be consistently safe and reliable for human consumption. This assurance of water quality allows for its integration into the potable water supply system. Groundwater replenishment, when used for potable water supply, expands the available freshwater supply [101]. By utilizing advanced treatment technologies to convert treated wastewater into a reliable source of potable water, communities can augment their water resources and overcome water scarcity challenges [102]. This is particularly important in areas facing limited freshwater availability, growing population demands, or environmental constraints on traditional water sources [103]. Groundwater replenishment offers the advantage of diversifying water sources for potable water supply [91]. By adding treated wastewater into the water supply portfolio, communities can reduce their reliance on traditional sources such as surface water or groundwater extraction from diminishing aquifers [104]. This diversification enhances water supply resilience, ensuring a more secure and sustainable water system. It also helps mitigate the risks associated with single-source dependence or potential vulnerabilities to drought, contamination, or climate change impacts. Groundwater replenishment can be a cost-effective alternative compared to developing traditional water supply infrastructures that involve long-distance water transfers, desalination plants, or large-scale dam projects. By utilizing existing or upgraded wastewater treatment facilities and utilizing the natural process of aquifer storage and recovery, the need for extensive and expensive infrastructure projects can be minimized. This can result in significant cost savings for communities while still ensuring a safe and adequate potable water supply. Groundwater replenishment for potable water supply offers environmental advantages [105]. It encourages the reuse and recycling of treated wastewater, reducing the demands on freshwater sources and minimizing the discharge of treated wastewater into surface water bodies. This contributes to the conservation of freshwater resources, protects ecosystems from pollution, and promotes sustainable water management practices. In rundown, coupling groundwater replenishment processes with advanced treatment technologies enables the production of high-quality water suitable for potable water supply. This increases the overall freshwater supply, diversifies water sources, reduces reliance on traditional sources, and minimizes the need for costly infrastructure projects. Through this innovative approach, communities can address water scarcity, enhance water supply resilience, and contribute to sustainable water resource management.

5. Conclusion

In water-scarce regions such as the Middle East and North Africa (MENA), water has a valuable value and must be accounted for every drop. It is therefore necessary to reclassify wastewater as a renewable source of water rather than waste, in order to make it more effective at increasing water availability and preventing environmental pollution. Utilization of this asset requires collection, treatment, and distribution of all produced wastewater. In spite of the fact that reuse of wastewater is recognized in most water-scarce nations, the reuse of wastewater is still exceptionally very low. It is generally discarded as waste once freshwater has been used for an economic or beneficial purpose. In many countries, these wastewaters are discharged, either as untreated waste or as treated effluent, into natural ecosystem like watercourses, from which they are abstracted for further use after undergoing “self-purification” within the ecosystem. Wastewater may be reused more than a dozen times before it is released as part of the system of indirect reuse. However, it is also possible to use it more directly. Wastewater treatment contributes to economic and environmental sustainability, such as converting waste into clean water, converting into energy, thereby reducing the impact on the environment caused by wastewaters or building sustainable industrial cities and towns. For the purpose of providing clean drinking water and other uses, wastewater treatment removes pollutants, neutralizes particulate matter, removes toxicants, and kills pathogens. Wastewater treatment eliminates waste by ensuring that valuable products, such as energy, clean water, and fertilizers, are converted into dirty water that would otherwise be disposed of. The treatment of wastewater also provides sufficient nutrients to increase crop yields when used for agricultural purposes. The treatment of wastewater prevents exposure to potentially toxic chemicals, which can lead to severe diseases. One of the most sustainable ways to achieve a sustainable energy supply is to recover energy from wastewater. Constructing wastewater treatment plants is the first step to reducing waste and making sure that things that would have been wasted are reused. Wastewater treatment plants can make enough clean water for cities and suburbs that do not have enough water. Moreover, cleaning wastewater helps to prevent harm to the environment when it’s released into rivers, lakes, and oceans. Making more clean water available would mean less scarcity and lessening the strain on natural resources. Managing resources sustainably means making sure we always have enough for the future, so we do not use them all up. Therefore, institutions and policy capacity need to be enhanced, public awareness of related issues needs to be strengthened, and appropriate funding mechanisms set up in order for the successful implementation of wastewater reuse strategies.

Conflict of interest

Authors declare no conflict of interest.