The technological changes of recent years have generated multiple economic, social, and environmental opportunities. Different economic sectors have achieved greater flexibility and individualization of products and services, as well as greater control of manufacturing and distribution processes. However, this technological change also becomes a challenge in many aspects, such as the large investments needed to implement the new advances and accomplishing security and privacy policies to ensure the availability of data and information. In this sense, new technological opportunities are perceived that need tools that help implement the benefits of the use of information technologies in various areas, such as employment, wages, health, safety, and resource efficiency [1
]. Nevertheless, to take advantage of the multiple benefits that the implementation of these new technologies generates, it is necessary to have an adaptation period of our society to become used to it [2
When talking about technological change concerns referring to the concept of digitalization, this is understood as the process of converting analog data to digital data. This transformation implies the use of new platforms and business models which are based on the use of technologies, devices, or digital techniques that enable monitoring of production systems simplifying business processes, improving the security systems in transactions, infrastructure, and the economy. Digital transformation makes it possible to restructure economies, institutions, and society at the system stage [5
], which implies changes at all social levels. In addition, digitalization allows the combination of different technologies to result in new products and services [6
], as well as increasing the efficiency of current processes, while reinforcing the sustainability of the economic model.
The benefits of digitalization in the current economic system are the backbone of the change in this model, as they make it possible to increase connectivity between companies and create more effective and efficient systems, which becomes a significant competitive advantage. At the same time, the existence of large volumes of data permits a detailed analysis of both local and global impacts generated by the consumption of products or services. The subsequent processing and interpretation of the data provides a better understanding of the economic model and the behavior of the system, combining social, economic, and environmental perspectives.
The current prominence of digitalization is echoed in the Circular Economy Action Plan and the European Green Pact adopted by the European Commission in 2020 [7
]. One of the goals of these action plans is to build a digital sector around sustainability and green growth. Digitalization is proposed as a key tool to achieve sustainability goals in different industrial fields. Through these programs, the European Union seeks to explore and promote digital technologies to accelerate and maximize the impact of these European policies on managing climate change and the protection of the environment. In this way, Europe will become the first climate-neutral continent by 2050 by implementing measures throughout the entire life cycle of products, protecting the environment and giving the consumers new rights.
In Spain, there is the Spanish Circular Economy Strategy, Circular Spain 2030 [8
], which lays the foundation for the promotion and implementation of the circular economy on the following axes: production, consumption, waste management, secondary raw materials, and water reuse. In all of them, it is possible to see the possibilities that digitalization offers to accelerate the transition to a circular economy model. The current economic model is based on a constant flow of raw materials (generally non-renewable) to be transformed into products and services that are essential for the functioning of society. This economic model is unsustainable due to the short life cycle that these products and services have, generating large quantities of waste that are complex to manage, and accelerating the consumption of new products and services [9
]. This situation leads to severe environmental problems both on the production level (high extraction and production rates) and on the waste management level (tonnes of waste must be managed every day in order to avoid ecosystem degradation) [10
One of the axes to consider in the implementation of digitalization is the importance of the circular economy and its impact on the economic model. The purpose of a circular economy is to detach economic growth from consumption of natural resources and environmental degradation. In this regard, the circular economy is conceived based on a cycle of development and transformation, which advances by optimizing the use of resources, promoting the efficiency of production systems, encouraging that products, materials, and resources remain functional for as long as possible, and, in parallel, reducing the amount of waste generated [11
]. In particular, the circular economy relies on the use of the four “Rs”, reduce, reuse, repair, and recycle, to provide feasible and sustainable solutions to the problems presented by the current economic model, including urban water cycle management.
The aim of this paper is to analyze the potentiality of digitalization as an effective tool for the management of natural resources and, more specifically, to demonstrate that the digitalization of the urban water cycle is the future of water management. The pressure on conventional water sources is currently a challenge to meet water demand in terms of quantity and quality. Not only is the quality of freshwater worsening year by year, but also the volume of water has declined due to increasingly frequent and prolonged periods of drought attributed to climate change [12
]. Such a situation makes it necessary to implement new management approaches that provide detailed and real-time information on the condition of water resources. For this reason, the role of the circular economy becomes particularly significant in the context of the water sector. This is because water is a very valuable resource that is vital not only for human life and organisms, but also for economic sectors. The availability of freshwater, both in quantity and quality, is a key element for generating and sustaining economic development. In short, digitization permits monitoring water flows, but also allows the identification of water volumes available for their reuse, fostering and enhancing the circular economy approach in the water sector.
3. Digitalization as a Tool for Natural-Resource Management
Natural resources are a very prominent component of the world economy. The management of natural resources requires innovative methodologies to monitor and understand the life cycle of products, goods, and services, as well as to identify opportunities to convert waste generated into raw materials for other industrial processes. The development of technologies leads to progress towards a rational use of natural resources and the protection of the environment. This is possible due to the large amount of information regarding the quality of air, water, land use, flora, and fauna, and other aspects related to energy use and the production of noise, waste, and emissions [15
There are many sectors that use technological innovations in their processes. For example, in the agricultural sector, sensors are used to monitor the variables that affect production, thus optimizing food production [16
], increase the precision of fertilizer, pesticide, and herbicide application [17
], determine optimal crop sowing dates, or to help identify and remove weeds [18
]. In the fish sector, satellite systems based on optical sensors provide numerous physical parameters of water and location of fishing vessels, underwater drones determine the optimal areas to fish, and other devices analyze the volume and biophysical characteristics of the fish caught, providing a large information about the supply chain [20
]. Similarly, in the farming sector, data collected by sensors (such as cameras, microphones, accelerometers, gas analyzers…) about animals or their environment, together with sophisticated analytical techniques, provide efficient tools to monitor animals to improve their welfare and optimize the use of resources, such as feed, water, and land [21
]. Some tasks are even performed by robots, such as cattle milking [22
] or automatic feeder dispensers [23
In this context, the European Union identifies as Key Enabling Technologies those knowledge-intensive technologies that are characterized by a high degree of R&D [24
]. They are considered as innovation drivers in multiple sectors with a strong potential to bring major social, economic, and environmental changes. Table 1
lists the main digital methodologies currently available for data and natural-resource management which will allow a transition from the current practices of data processing to the new digital model.
The EU’s digital strategy seeks to make this digital transformation and adaptation work for people and businesses before 2050, while contributing to the goal of a climate-neutral Europe. Digital technologies offer a range of tangible benefits that are not only economic, but also social and environmental, enhancing even further the advantages of their implementation. This is because they offer a wide range of solutions that in turn allow reduction in the environmental impacts generated and reallocation of resources in a more efficient way.
This is why some sectors, such as energy, waste, and water, show great potential for integrating these digital tools into their processes. For instance, in the case of water, it is a scarce resource that requires constant monitoring to ensure both its quality and quantity to meet water demands, and once it is used, it should be treated to reduce the environmental impact when it is discharged. In this last process, multiple resources such as water, fertilizers, sludge, and biogas can be obtained [31
]. Technology helps to use reclaimed water for other uses, reducing the pressure on the conventional source. For all these reasons, the urban water cycle represents numerous opportunities for digitization in each of its phases. The large number of technical and economic indicators generated from catchment to distribution and treatment provide valuable information that can be used to optimize drinking water treatment and distribution processes, generate consumption scenarios, reduce energy costs, and extend the useful life of assets and infrastructure. In recent years, artificial intelligence technologies have been increasingly applied to transform data into actionable knowledge to improve the performance of urban water cycle infrastructures and support the operation and maintenance decision making [33
However, all new approaches present certain barriers of access due to the novelty of their conception and the technological limitations associated with their implementation on a small and large scale. These barriers need to be identified in each specific case in order to deal with them, so that digitization can be carried out effectively. In this sense, Marcon et al. (2019) [37
] identified the most important factors that slow down this digital progress in companies. The conclusions of this study can easily be transferred to companies that manage the urban water cycle. Firstly, the financial aspects are the most difficult, due to the complexity of quantifying the returns of investment in digitization. Secondly, the lack of knowledge and skills of personnel in the area of digitalization can cause some difficulties in adopting new systems, leading to some resistance to change. Thirdly and lastly, there are security and risk issues that the transfer of data between sites creates for the organization.
4. Framework for the Application of Digitalization in the Water Sector
Water is an essential resource both for people and the economic activity of any sector. Hence, it is imperative to ensure a secure, predictable and, above all, a high-quality water supply. In this sense, it is important to point out that the overexploitation to which groundwater is subjected can generate changes in the quality of this resource. Chemical pollutants from human activities, such as industry and agriculture, can cause variations in physic-chemical parameters such as turbidity, pH, electrical conductivity, dissolved oxygen, chlorides, nitrates, and phosphates, posing a potential risk to human health [38
]. The growing demand for water, coupled with a reduction in water resources, is leading to an increasing interest on the part of State Members in conceiving water as a scarce economic resource with growing value that requires new sources of supply to ensure the continuity and sustainability of the hydrological cycle. In addition, there is a growing concern to monitor and guarantee the quality of the water supplied by infrastructures, because factors such as stagnation of drinking water or seasonal variations in the quality at source can deteriorate its condition, posing a long-term health risk [39
]. In this sense, studies such as Ji et al. (2020) [40
] corroborate the importance of monitoring the quality of the water supplied in order to reduce the likelihood of associated diseases.
Current water scarcity has global consequences on the population, the environment, and the economy. This situation is forcing administrations to take action to promote not only conservation but also reuse and the circular economy. This is the case of the United Nations 2030 Agenda for Sustainable Development, which comprises a collection of 17 sustainable development goals (SDGs) that seek the social and economic development of territories and the conservation of the environment, where SDG 6 stands out on the management of water and sanitation.
The urban water cycle offers great opportunities for the implementation of digitalization throughout all its stages. Adequate digital processing of information flows enables greater control of logistics at all levels, from predicting water demand to controlling waste generated to ensure its reuse within the appropriate channels [41
]. In order to guarantee water supply, a series of infrastructure is required to store water, make water drinkable, and distribute and treat it after its use. The set of processes that run from catchment and supply to wastewater treatment and discharge is called the urban water cycle (Figure 2
This infrastructure requires a large amount of energy, both to guarantee the correct operation of the different treatments and to pump the water. In total, for the country as a whole, an estimated annual urban supply water flow of 3730 hm3
and a volume of treated wastewater of 4450 hm3
is estimated. The difference between both quantities can be justified by the fact that there does not exist a separative network of rainwater and WWTPs could receive water from other effluents. In addition, the water sector is characterized by requiring a large amount of energy, both to guarantee the correct functioning of the different treatments and to pump the water. These infrastructures consume 447 GWh/year of electricity in pumping for the collection, supply, and distribution of urban water, and 2225 GWh/year of electricity for treatment processes. In this regard, the analysis of final energy consumption in Spain highlights how oil and its derivatives accounted for almost 51% of final energy in 2018, followed by electricity (23%) and natural gas (16%). As a result, more than 75% of energy supply currently depends on non-renewable sources such as coal, oil, and natural gas, which contribute significantly to carbon dioxide (CO2
) emissions [8
In recent years, digitalization has been implemented in many of the activities involving the water sector [42
]. From the point of view of infrastructure design and operation, digitalization enables the integration of several aspects such as planning, engineering, and operation. Through the automatic updating of planning data during plant operation, the actual condition of the facilities and the different systems of the distribution and sewerage networks can always be visualized, resulting in a more efficient and effective management of the networks.
In the urban water cycle, digitalization allows the use of different tools in a complementary manner (Figure 3
). Firstly, the water collection and treatment processes generate a large amount of data that is gathered through sensors, such as flow rates, energy, reagents, and required maintenance, among others. Its continuous monitoring enables operators to anticipate demand peaks, thus adapting the flow rates treated and maximizing the availability times. Furthermore, the control of possible variations in the organic load makes it easier to adapt the treatments, minimizing the use of reagents in the treatment processes.
Secondly, digitalization permits the monitoring of its distribution to households, industries, and businesses. In this sense, it facilitates the detection of possible leaks in the network, as well as changes or anomalies in the consumption of water, improving the water efficiency of the system, which results in lower energy consumption in the network.
Thirdly, digital tools offer the possibility to monitor wastewater flows discharged to the sewage system, either to detect large fluctuations in the volume of wastewater produced or to detect peaks in the organic load. This information is highly useful for Wastewater Treatment Plants (WWTPs), since the collected data allow planning of operational tasks, adjusting the reagents and energy needed to ensure the correct functioning of the process.
Fourthly, the monitorization of treatments in WWTPs allows the automatization of processes, improving the efficiency of this infrastructure. The benefits of digitalization have a direct impact on reducing the costs of the process while maximizing the benefits obtained by controlling waste to generate resources for other uses: sludge for agriculture, fertilizers, and energy, among others.
From the operational point of view of the facilities, the application of the cloud computing system allows the integration of volumes of data generated from the monitoring and measuring systems for water quality, energy consumption, and reagent usage. The cloud computing system processes data and visualizes the operation of the wastewater treatment process, energy consumption, and cost analysis. In such a way, with the help of digitalization, it is possible to generate a digital twin of the complete process. Digital twins are generated to simulate scenarios such as variations in flow rates, rainfall, and organic loads, among other aspects. This simulation allows the operator to plan different alternatives in a real environment, helping to reduce costs and improve energy efficiency while minimizing the risk of spillage. Another aspect in which digitalization offers numerous advantages is the centralized management of the physical assets of the facilities. Its constant monitoring and the application of algorithms make it possible to reduce the risk of breakdowns and the costs associated with the life cycle based on historical data, as well as better planning of the most effective maintenance tasks and the establishment of a plan for renewal and investment in new equipment and infrastructure.
However, it is in the drinking water treatment and the distribution network where digitalization has been gaining more attention in recent decades through the installation of smart meters and the sectorization of the network [43
]. In terms of remote reading, smart meters allow users to consult their own water consumption in real time through applications hosted in the cloud. The software provides an alarm in case of a sudden increase in consumption, detects possible occupancy of second homes, or informs about risk situations for vulnerable people living alone, in the event that a stoppage is detected in the consumption. The meters provide an accurate billing of the service, avoiding estimated consumption by households, industry, or businesses, thus providing greater transparency and quality in the service provision. In turn, the data obtained are connected to the Drinking Water Treatment Plant (DWTP), which collects and analyses daily data about the quantity of water supplied or the flow rates and pressures in the network.
Loss of drinking water in the distribution network is one of the biggest problems for operators, involving high economic losses as well as becoming a significant contributor of inefficiencies in the process. Sectorization permits the assessment of a water balance delimited by geographical areas, neighborhoods, and buildings. It helps to identify and quantify potential losses of drinking water and, consequently, allows operators to take more effective measures. In this case, digital tools dedicated to monitor incoming and outgoing flows and the geolocation of the networks are combined. Subsequent analysis of the data enables real-time alarms to be set up.
In conclusion, digital transformation allows the integration of new technologies in all areas of the urban water cycle. The monitorization of infrastructure, processes, and consumption generates large amounts of data that should be processed through an advanced analysis [44
]. The information obtained will give clues to reduce energy consumption, improve productivity, increase the efficiency of the facilities, and extend the life cycle of the assets, guaranteeing the sustainability of the system. In addition, the results obtained can be combined with other sectors, for example, agriculture, thus guaranteeing practical viability for the resources generated by the WWTPs and facilitating the integration of the circular economy.
5. The Capacity of Digitalization to Promote the Circular Economy in the Urban Water Sector
The water reuse sector could take great advantage of the implementation of digital technologies since it could help to manage more efficiently reclaimed water and other subproducts among final users. It should be mentioned that reclaimed water can be used by different economic sectors such as industry, agriculture, and services. For instance, industry can make use of reclaimed water for its production processes. The agricultural sector can use reclaimed water but also the sludge generated, as well as the fertilizers obtained from nitrogen and phosphorus. Moreover, wastewater treated at WWTPs can have an environmental purpose, such as to guarantee ecological flows, irrigate forest areas, restore ecosystems (marshes), or help to recover aquifers through infiltration.
The combination of the different uses of the subproducts generated in the wastewater treatment process and the quantities required by each actor constitute the total number of opportunities that the circular economy represents for the urban water cycle sector. Therefore, it is vital to align the supply of resources generated by urban water cycle infrastructures with the demand of the other sectors. The aim is to optimize the relationships in order to maximize the benefits generated [45
]. In this sense, digitalization offers the possibility to respond to these new requirements, acting as a facilitator of improvements in the circular economy in the water sector (Figure 4
Regarding the agricultural sector, water use must be regulated to reduce the negative effects of climate change. This involves modernizing the sector through new irrigation systems to optimize the consumption of water and to use reclaimed water as an alternative source [46
]. In this respect, digitalization makes it possible to know in detail the water requirement of different crops based on different variables (climate, soil type, crop) and to connect these needs with water flows that can be reclaimed to provide the agricultural sector with a sufficient quantity and quality of water. In addition, the need for fertilizers, mainly phosphorus and nitrogen, can be partly satisfied by WWTPs, and these concentrations can be monitored and controlled depending on the demand. This is possible thanks to the sectorization of irrigation channels.
Finally, the sludge produced in the wastewater treatment process, if managed correctly, can be used as compost, improving soil properties, or improving the deficit of some parameter, as it contains a considerable amount of organic matter and nutrients. The amount of compost to be used depends on different variables such as soil type, crop, or nitrogen limit per hectare. Again, synchronizing the data related to the demand of the sub-product and the production capacity of WWTPs enables planning of its use, adapting it to agricultural needs [47
In the industrial sector, for example, the ceramic industry has intensive use of water in its production processes; this industry consumes a large volume of water in its manufacturing processes. The use of reclaimed water in some production processes would reduce the extraction of freshwater, reducing water stress [48
]. Digitalization and subsequent synchronization of water demands by the industrial sector would again help to adjust the necessary quantities of reclaimed water, increasing the efficiency of the process.
Finally, in urban areas, the uses of reclaimed water are diverse. At the service level, it is possible to irrigate municipal gardens (parks, sports fields, and similar), street washing, fire-fighting systems, vehicle washing, or conduct irrigation of the forest–urban interface [49
]. The water needs of different uses can be planned and digitalized in order to optimize reclaimed water consumption, for instance, irrigation of public gardens or street washing can change depending on rainfall. In turn, the quantities of water required can be a function of size and, finally, irrigation scheduling can be determined by other aspects related to temperature. Algorithms allow modeling of different variables, offering solutions based on real-time automated calculation. Synchronizing these solutions with the regeneration process in WWTPs allows the infrastructure to plan water production for each type of use, regenerating and storing water to ensure its availability in the quantity and quality required for each use.
Digital technologies and data are generating multiple benefits, since digitalization enables economic transformation that is geared towards human, social, and environmental progress. The connectivity offered by digitalization allows companies to create more effective and efficient systems based on the analysis of large volumes of data. In addition, digital tools can be used to measure the implications of the new economic model on the environment and climate change. For this reason, the European Union is implementing an ambitious plan to promote digital technologies through the European Green Deal.
One of the potentialities of digitalization is its capacity to accelerate and favor the transition towards an economy that is more environmentally friendly and aligned with the planet and the well-being of citizens. Digital technologies facilitate the tracking, tracing, and mapping of resources, enabling circularity in production processes. This circularity enables the use of resources based on reduce, reuse, repair, and recycle. This model of resource management establishes a circular cycle that avoids the waste of natural resources.
A good practical illustration of the potential of digitalization is the urban water sector, where the digital transformation of these infrastructures and pipelines makes it possible to improve their management through the continuous control and monitoring of processes. The use of sensors is particularly relevant due to the large number of assets, providing real-time data on water quality, flow rates, pressures, and water levels, among other parameters. A wide variety of sensors, both fixed and mobile, can be distributed throughout the systems to support daily operations by optimizing the use of resources, proactively detecting, diagnosing, and preventing damage, and providing useful information for prevention, maintenance, and long-term planning.
Smart technologies are conceived as innovative tools and their integration will benefit the three essential elements of the food, water, and energy nexus. The growing global demand for food requires technological solutions that optimize resources. For example, the use of the IoT and agricultural unmanned aerial vehicles (UAVs) can improve irrigation of agricultural land, reducing water use while improving the efficiency of fertilizer and pesticide use for pest control. Crop monitoring through the use of sensors and image analysis algorithms allows the control of certain soil parameters in order to detect nutrient deficiencies, warn of possible pests or weeds that could damage crops, or monitor crop yields, thereby increasing agricultural efficiency.
Ultimately, these and other examples of digitalization help to protect non-renewable natural resources. By implementing models based on the circular economy, it is possible to obtain fertilizers and water and generate clean energy. With regard to water use, agriculture accounts for around 80% of total consumption, so the use of reclaimed water in crops is an opportunity to address the water crisis that many countries are suffering. Beyond the use of water, the transformation of waste into resources represents an environmental protection within the framework of the EC. The use of these resources avoids the exploitation of conventional resources, making it possible to move towards sustainability.
Digital platforms allow data to be shared in real time, strengthening collaborative networks between different productive sectors. Participants not only contribute data, but also help to refine the design, analyze the data, or disseminate conclusions, thus optimizing the use of resources.
In this respect, the possibility of digitalizing different productive sectors poses a challenge for the current economic model, which is aligning the strategies of different sectors to move towards the implementation of a circular economy, thus increasing efficiency in terms of resource use.
The monitoring of the production system, the use of big data, and the possibility of modeling different patterns generates a large amount of data that can be used. This study explains, specifically in the case of the urban water cycle, how different economic, agricultural, and industrial sectors can take advantage of the potential of digitalization. The possibility of making use of reclaimed water in their production processes, as well as taking advantage of sludge or fertilizers, makes it possible to generate new business models based on the circular economy. Furthermore, being aware of the reclaimed water demand of urban areas (gardens, street cleaning, etc.) will permit planning of the necessary treatments to adapt the water to different uses. Synchronizing the needs of all the agents involved, using digital tools, leads to greater efficiency, generating a new three-way collaboration model between the public and private sectors and citizens.