Water Management and Circular Economy

Water Management and Circular Economy covers the role of water in the mainstream dimensions of society, economy, environment/ecology and technology. Along with the under conceptualization of the Circular Economy (CE), the book covers the role of recycling and reusing the otherwise lost sources of waste, gray or untapped water sources towards a second round of utility. This book bridges the gap between water inflows in nature with the wide spectrum of its potential applications in humanity. Sections cover direct and indirect entities conceptualized as “outflows, including water, energy, products and services to urban, suburban, rural and insular contexts of analysis.

As such, this content will be important reading for Water Scientists, Water Managers, and civil engineers.

• Includes real-world applications and case studies to show how these policies can be adopted
• Presents global coverage, with a diverse list of contributors – all of whom are experts in the field
• Showcases a multidisciplinary approach, with editors from environmental and managerial backgrounds, thus helping to cross the bridge between social and science fields

• Language: English
• Publisher: Elsevier Science
• Release date: Aug 7, 2023
• ISBN: 9780323952811

Book preview

Preface

The "Water Management and Circular Economy book covers a wide range of technological, environmental, socio-economic, ecological, regulatory, and public health dimensions that are related to contemporary water management advancements. Based on the circular economy (CE) principles the book covers the decisive role of recycling and reusing the otherwise lost sources of waste, gray, or untapped water sources towards a second round of utility. This book also enhances our knowledge and comprehensive understanding of how water inflows in nature can meet a wide spectrum of potential applications in humanity. Therefore, the book sections have been focused on the direct and the indirect utilities of water management not limited to the aqueous outflows, but they have been also extended to include a variety of water, energy, products, and services to urban, suburban, rural, and insular contexts of analysis. Another interesting feature of the book is the geographical dispersion of water management applications and planning, covering the prevailing technological, legislative, regulatory, financial, and marketable perspectives of water management worldwide, especially concerning its circularity prospects and potential. As such, Water Management and Circular Economy" is a timely important book and interesting reading for graduate and postgraduate students, university researchers and lecturers, water managers, scientists in the fields of civil- (especially the section of water engineering), hydro-, chemical-, environmental-, ecological-, rural-, and surveying-engineering, as well as for public health and environmental law readers.

The editors

Miltiadis G. Zamparas and Grigorios L. Kyriakopoulos

Part I

Introduction and Fundamentals

1. Closing the loop in water management 3

2. Selecting resource recovery technologies and assessment of impacts 25

3. Circularity in wastewater allocation as a solution for increased water availability: A focus on optimization methods and applications 39

Chapter 1

Closing the loop in water management

Hernan Ruiz-Ocampoa,b, Vlatka Katusica,b and Giorgos Demetrioua

aCircular Economy Research Center, Ecole des Ponts, Business School, Marne-la-Vallée, France

bCircular Economy Alliance, Nicosia, Cyprus

1.1 Introduction

The water cycle is a complex system of activities and processes involving flows and storage. Water is present in oceans, ice sheets and glaciers, snowpacks on top of mountains, lakes, rivers and streams, reservoirs and water sheets, wetlands, soil and plants, water tables, and underground aquifers (groundwater). All storage is temporary, and water is constantly in flux and moving, involving processes such as precipitation, collection runoff, interception, infiltration, percolation, discharge, transpiration, evaporation, condensation, and evapotranspiration.

The interaction between the water cycle and human activities creates the need to adapt the natural water cycle to economic activities, considering that only 1% is accessible surface water (Boberg, 2005). Water sources from surface water, such as lakes, rivers, reservoirs, etc., are extracted from natural environments for human activities, often using pumping methods. Using groundwater requires implementing wells, and seawater requires a desalination process. Drinking water treatment involves different techniques depending on the source and composition of water (filtration, disinfection, etc.). After treatment, storage should ensure continuous availability to distribute water for domestic and industrial consumption. Collection systems need to convey the water after usage to wastewater treatment plants. However, 80% of global wastewater is disposed to the natural environment without treatment (WWAP, 2017). Current water sector activities reflect the linear economy. Generally, the water extracted from the natural environment is only used once before discharging into natural water bodies and usually without appropriate treatment before disposal.

Linear economy in the water sector

Ensuring sustainable water supply and wastewater treatment is one of the challenges in the upcoming years. Today, more than 50% of the population lives in urban areas, increasing pressure on urban water supply. By 2050, urban areas will host 70% of the global population, pushing agriculture, industrial, and domestic water demand to grow and increasing the pressure on water availability. Water is crucial for developing society, the economy, and the environment since 90% of the global economy depends on water. Water stress is growing due to unsustainable water use, and the demand will exceed 40% of the supply capacity by 2030.

In the past, water management primarily focused on increasing supply by drilling new wells, building dams and reservoirs, desalination, large-scale water-transfer infrastructures, etc. However, the water supply cannot endlessly increase, and citizens and industrial sectors must reduce demand. The different challenges, such as floods, droughts, and scarcity, show the need to reshape water management and build a resilient water sector prepared for future challenges.

Climate change is also putting pressure on wastewater facilities during heavy rain episodes due to the sudden increase in water volume and the need to ensure sufficient capacity in the sewer systems to prevent overflows. The impacts of climate change are related to increasing temperature, precipitation, glaciers and snow, evapotranspiration, and droughts. Water-related hazards dominate the list of disasters regarding the human and economic toll over the past 50 years (1970–2019). Of the top 10 list, the hazards leading to the most considerable human losses were droughts, storms, floods, and extreme temperatures (WMO, 2021). For example, in Europe, water scarcity and shortages seasonally increased in countries such as France, Cyprus, Spain, Italy, and Romania because of overexploitation and changes in rainfall patterns (European Environmental Agency, 2018; Gabarda-Mallorquí et al., 2018).

Climate change intensifies the water cycle, affecting rain patterns and bringing more intense rainfall in high latitudes creating floods. In contrast, more intense shortages will occur in other regions. Sea levels will continue increasing in coastal areas in the 21st century, originating frequent and severe coastal flooding in low-lying areas and coastal erosion. Cities will suffer from increased heating since urban areas are usually warmer, from floodings related to heavy precipitations and sea-level rise in coastal cities. Extreme sea-level events that occur once in 100 years might increase to a yearly recurrence (IPPC, 2022). Cities showed fragility to face natural disasters and the need to implement adaptative measures to deal with a changing environment and reduce the risk for coastal communities, properties, and other assets. Climate change will also impact the hydrological cycle of soil moisture content, groundwater recharge, and river discharges. In agriculture, droughts can lead to low soil moisture content, causing losses in crop yields. Depleting groundwater storage can disrupt the drinking water supply and damage high-added-value sectors such as tourism and water-dependent industries. Lowing discharges in rivers will also affect water-dependent electricity production in thermal and nuclear power plants or hydropower facilities. At the same time, reducing water depth in free-flowing rivers will also affect inland shipping (European Environmental Agency, 2021).

Therefore, the need to shift to a more sustainable approach is self-evident to avoid natural disasters and foster water use during several cycles before reaching the natural environment, balancing the supply and demand of water resources. The circular economy (CE) envisions a regenerative system, minimizing the consumption of new resources and extending the lifecycle of current products (Heshmati, 2017; Kalmykova et al., 2018).

Applying a circular economy in the water sector presents an opportunity to accelerate and scale up recent scientific and technological advances, supporting greater efficiency in water infrastructures. The general idea assumes that the water cycle management needs to be from catchment to consumer, back to the catchment. However, the fragmentation in the water industry can hinder the adoption of innovative solutions and a collective vision for the future of water, slowing the diffusion and funding opportunities of new technologies throughout the industry. Therefore, the transition to the CE model has to consider the consumption and production of resources throughout the entire value chain and create connections within the water cycle for more efficient synergies outside the water sector. To increase the efficiency of water use, a transformational change in implementing new business models can foster the extraction of value from water at all levels (river basin, city, industry, building, agriculture) (Morseletto et al., 2022). The transition towards a water-smart society and the circular economy involves a holistic approach integrating, replacing, and transforming complex social and technical regimes with adaptative and flexible urban water systems.

In this sense, the present study aims to provide a holistic practice overview of implementing the circular economy in the water sector. The first part reviews the different frameworks aiming to provide strategies to implement the circular economy strategies in the water sector, transforming water utilities in resource recovery facilities. The following section analyses the linkages between circular business model strategies and the various water frameworks, highlighting the need to include digital technologies to enable the circular economy as part of holistic water solutions. Finally, the last part describes how implementing an ecosystemic approach through real-life experimentation involving different stakeholders and end users can allow the implementation of tailored circular solutions adapted to different contexts and situations.

1.2 Methods

A well-defined approach to selecting and reviewing the appropriate content consisted of a four-step plan that includes identifying, selecting, classifying, and evaluating the relevance to the circular and digital transition in the water sector. Using keywords helped narrow the search and identify relevant sources of information to analyze the most pertinent data efficiently. Moreover, combinations of keywords facilitated the identification extension by using familiar operators such as and, or, and not. At the same time, different keywords reflecting a wider area of interest helped reach more content, and the selection step helped specify the relevant literature. The keywords used were: water, circular economy, strategies, wastewater, experimentation, circular business models, water management, and digital water.

A key consideration in identifying appropriate research material was the source of information. Scientific literature, such as existing systematic reviews, offered a good overview of the research on various topics. The literature review considered databases such as Elsevier Scopus, Elsevier ScienceDirect, Google Scholar, ResearchGate, and available publications such as papers from conference proceedings. The study also considered literature such as commissioned reports, organizational projects, working papers, government documents, white papers, evaluations, etc.

To accurately select the most relevant content, the selection criteria included articles in English up to 2022, containing an explicit methodology for defining, e.g., different frameworks for implementing the circular economy in the water sector and comparing them allowed to identify possible gaps and challenges. The final selection included a total of 60 references. The classification of the selected information allowed us to identify three main concepts: circular economy in the water sector, digital technologies enabling circular economy, and circular business models. Subsequent in-depth scanning of the relevant documents allowed us to make connections, compare, critically evaluate, interpret, and draw conclusions across different information sources analyzed.

1.3 Strategies for circularity in the water sector

Water is a resource for open innovation in different applications. Natural capital includes rocks and minerals, fauna, flora, and biodiversity. But also, water is a unique and irreplaceable resource; without water, there is no life, and caring for natural resources is essential for long-term stability. The circular economy is a new business model that aims to decouple growth from resource extraction, having a societal impact, economic implications, environmental advantages, and a disruptive effect.

Implementing tailored water technologies to respond to a specific need will optimize the energy, minerals, and chemicals used in operating water systems solutions. Modular water utility design will permit the adaptation of requirements imposed by the legislation to guarantee the water quality of water bodies. Technologies should allow efficient wastewater treatment, reclaimed water with different quality levels, and provide recovery facilities for nutrients, metals, minerals, and energy to support the transition to the circular economy.

Some waste prevention methods are available, known as the R-strategies, including refuse, rethink, reduce, reuse, repair, refurbish, remanufacture, repurpose, recycle, and recover (Blomsma & Brennan, 2017; D'Adamo et al., 2022; Morseletto, 2020). However, some of these strategies refer to general applications and types of industrial production that do not fit the water context (Oduro-Kwarteng et al., 2016; Sakai et al., 2017). The authors of CE literature have not widely focused on clearly defining and ordering this fundamental concept of R-principles. Many R frameworks and definitions range from 3Rs to 10Rs (Homrich et al., 2018). Each R-principle has its purpose, and they are different in terms of their loop type (small, medium, and long) (Reike et al., 2018).

Embedding circularity in the water sector aims to ensure enough water for use across all industries while respecting environmental flows (Dolan et al., 2021; Rögener, 2021), considering more efficient and effective models for managing sustainable water management (Bakker, 2014; Sauvé et al., 2021; Scholz, 2018). Divers studies provided practical frameworks to define circular strategies applied to the water sector (Table 1.1).

Table 1.1

Circularity in the water sector presented in the White Paper developed by the Ellen MacArthur Foundation in 2018 focuses on giving the main CE principles and their connections to sustainable water management, including the intersection with diverse topics considering water as a carrier of chemicals, particles, and droplets (dissolved and suspended state) as a potential resource. The main CE principles proposed adapted to the water sector include (1) the design out of waste externalities, with a strong focus on optimization of water and energy, minerals, and chemicals usage, (2) keeping the resources in use, with a focus on the optimization of resource yields and energy or resource extraction from the water system, and (3) regeneration of natural capital by the reduction of consumption and non-consuming use of water (Tahir et al., 2018).

Moreover, a clear set of circular water strategies could support the transition in different sectors (e.g., energy, agri-food systems, sustainable consumption/production) by providing a practical framework to address the challenges of global changes. Implementing circular strategies will enable the circular economy in the entire value chain of the water sector. CE strategies are, therefore, the main pathways leading to a more circular use. Smol et al. (2020) proposed a circular economy framework for water and wastewater that includes reduction, reclamation or removal, reuse, recycling, recovery, and rethink. The framework proposed possible ways of implementing CE principles in the water and wastewater sector, including technology and organizational and societal changes. Integration of these solutions is a path toward CE in the water and wastewater sector. In another study, Morseletto et al. (2022) allocated the strategies into three categories: decreasing (avoid, reuse, replace), optimizing (reuse, recycle, cascading), and retaining (store, recover). There is no hierarchical implementation assuming that the same water is used multiple times for different purposes and contexts. In this model, water is a precious resource, product, and service to be managed sustainably within the natural water cycle (Table 1.1).

An innovative design will allow water utilities with resilient characteristics to provide adaptative and modular solutions. Resilient water utilities will allow combining processes to achieve different treatment levels according to the regulations and propose adapted solutions for the reuse and resource recovery of water, energy, nutrients, and raw materials. Water utilities should exploit the potential of water as a carrier of valuable resources (raw materials, nutrients) and play a more significant role in becoming a more substantial actor in different value chains. In addition, applying circular strategies might allow for overcoming inconveniences related to the regulatory environment and challenging market conditions (Delgado et al., 2021) (Table 1.1). Water utilities can shift from just providing water treatment to factories for materials, products, and services, allowing water quality for different requirements. Water utilities must transition from treatment plants to resource recovery facilities to include circular economy principles while ensuring high-quality treatment. Considering wastewater as a source carrier for materials and nutrients is a new perspective, demanding the development of innovative technologies at a large scale to ensure the quality of recovered materials and the markets on a commercial scale. Water facilities becoming smart water factories will facilitate the local flow of resources and materials (water, energy, nutrients, minerals, and metals) to create a systemic collaboration to foster the management of services in the water sector.

Following the frameworks described in Table 1.1, the design of water infrastructures must ensure the removal of pollutants and water quality. Applying multi-stakeholder governance will allow a rethinking of the entire water cycle with a collaborative approach, targeting the reduction of water consumption by implementing solutions for smart management, allowing the multiple uses of water through reuse and recycling. Constantly storing, restoring, and replenishing natural water sources will ensure a reliable water supply for future generations. The recovery of resources and energy will reduce the carbon footprint of water utilities to offer zero-carbon water services and create value from water by developing different products and services derived from the successful application of strategies. Thus, implementing innovative water technologies aims to transform water utilities into smart assets capable of ensuring the removal of pollutants and offering reuse, recycling, and resource recovery from water activities. Water streams are reusable resources and carriers for energy and components that can be extracted, treated, stored, and reused.

1.4 Enabling circularity in the water sector

1.4.1 Circular business models

Adopting the CE principles on a large scale inevitably leads to economic transformation and the establishment of new business models (Urbinati et al., 2017). CE changes the configuration of business models and supply chains, creates cooperative networks between different stakeholders, creating additional value propositions such as reuse, recycle, etc. (Table 1.2) based on the circular flow of resources (Bocken et al., 2016).

Table 1.2

A circular business model aims to define the rationale of how an organization creates, delivers, and captures value by applying five flow resource strategies: close, narrow, slow, and generate material loops (Bocken et al., 2016; Maria & Katri, 2016) and inform that includes the use of digital technologies in delivering new circular business models (Konietzko et al., 2020). Focusing on the five circular business model strategies will allow for maximizing the solution capacity by Narrowing the use of resources, creating reusable services that last longer, and slowing the use of products, components, and materials. The closing strategy will enable business activities to bring post-consumer waste back into the economic cycle, promoting and incentivizing product and component returns. Regenerating will create business activities to sustainably manage natural ecosystems using renewable energy and design products free of toxic materials. Finally, the information strategy will support using digital technologies to transition to the circular economy.

Following the different circular water frameworks presented in Table 1.1, the circular business model strategy of slowing aligns with the need to prevent wastewater generation by reducing water consumption and pollution and maximizing the use of existing infrastructures. It also relates to water reuse for non-potable usages with lower quality requirements (agriculture, flushing toilets, etc.). The closing strategy aligns with reclaimed water from wastewater for potable uses, where water recycling allows a high water quality to accomplish stricter standard parameters. It also includes cascading by providing different water usage and diversifying supply sources. Narrowing relates to the potential of water as a carrier for nutrients, minerals, and metals and their recovery as a source of materials for other industries and optimization of the operations in water utilities. Regenerate aligns with replenishing, restoring, storing, recharge natural water basins and bodies by managing stormwater, harvesting rainwater, etc. (Table 1.2).

Regarding the strategy Inform, none of the frameworks proposed explicitly includes the use of digital technologies to support the transition to the circular economy in the water sector (Table 1.2). This missed opportunity is not related to a technological gap but to the disconnection between water and computer engineering fields and limited practical experience (Garrido-Baserba et al., 2020). Moreover, the relationship between CE and digital technologies (DTs) is not a widely explored area because of the novelty of research on these topics (Bressanelli et al., 2018). Therefore, a proposition is to include a strategy named reconnect to implement new technologies, such as advanced sensors, monitoring, forecasting, augmented, virtual reality, digital twins, blockchain, and data processing (machine learning, artificial intelligence). Digital technologies will allow the implementation of decision support systems, early warnings, real-time monitoring, etc., to optimize water conservation and operations and reduce costs for water utilities.

1.4.2 Digital technologies enabling circular economy: reconnecting with water

A data-driven approach aims to materialize the CE and the integration with the digital infrastructure. Circularity involves prolonging, creating, and rethinking new use cycles of assets to increase their utilization, supply, and value chains while constantly regenerating natural resources. Digital technologies such as the Internet of Things (IoT), Big Data Analytics, Artificial Intelligence, etc., are enablers supporting the implementation of end-of-life strategies toward the transition to the CE.

Digital tools are part of our daily activities, where smart devices enable new forms of interaction and business models and, supported by green computing techniques, can increase the current utility of products (Soldatos et al., 2014). The study performed by (Hatzivasilis et al., 2019) showed that implementing a framework integrating the CE and IoT sectors can support the monitoring of the status of the assets, maintaining them regularly and proactively, limiting the equipment overworking during peak periods, and extending the beneficial lifecycle of damaged products. Through enabling properties of the assets, such as location, condition, and availability (LCA) (Antikainen et al., 2018), it is possible to harness the physical characteristics of assets and convert them into intelligent ones to obtain valuable insights and information about the performance. Tracking and monitoring the condition, location, and availability of products equipped with IoT sensors are necessary to generate value from the use-oriented business model (Uçar et al., 2020).

Applying digital technologies in the water sector can increase operational efficiencies and decrease timing, costs, and risks, enabling real-time monitoring of systems performance, allowing operators to test different scenarios, and ensuring greater confidence in decision-making (IWA, 2021). Advanced information analytics allow predictions concerning the maintenance of the monitored assets and discover potential problems well before they occur. Through monitoring, online machine learning algorithms can help to identify specific abnormal patterns within the streaming data (Kotsiantis et al., 2006). Monitoring refers to online real-time detection, while prediction relates to the short- or long-term estimation of critical events to minimize the risk of an infrastructure failure (Hatzivasilis et al., 2019). Data analytics performed at the backend allow the prediction of critical events using decision trees, support vector machines (SVMs), deep learning, and other machine learning time-series forecasting/prediction techniques (Längkvist et al., 2014) to enhance the overall business logic and the applied CE strategies.

Digital twins, for example, can help forecast system malfunction or predictive water levels, improve efficiency and productivity, and increase benefits for society, allowing for delivering safer, more sustainable, and more efficient waste and sanitation services (IWA, 2021). Digital twins can provide a digital representation of water systems by combining models and interaction with real-time data to simulate expected, desired, and critical behavior to improve infrastructure performance (Pedersen et al., 2021). Advances in instrumentation, such as cloud computing and the increasing availability of data in water facilities, attracted interest in implementing digital twins, improving operational efficiency targets, and lowering capital expenditures by providing more reliable control (Stentoft, 2020). Digital twins can support the transition towards more proactive water infrastructure management to mitigate disturbances before they adversely impact performance (Karmous-Edwards et al., 2019). Thus, there is a significant potential for economic savings, more effective protection of the environment through predictive control, and increased benefits for society in minimizing water-associated risks such as flooding in urban areas.

In an R&D project, the National Water Agency in Singapore (PUB) aims to create a digital twin in the Changi Water Reclamation Plant (CWRP) as an advisory tool providing insights regarding the operations and maintenance for increased productivity and enhancing operational resilience. Automated data inputs directly from the SCADA system, the laboratory information management system (LIMS), auto-calibration, and soft sensor capabilities will help to provide scenarios to enhance the water quality and optimize energy and chemical consumption. The digital twin inputs from SCADA are the various online flows measured and other relevant operational set points (concentrations, air rates, etc.). In combination with the LIMS data, a dynamic raw sewage influent file is generated, recreating the influent to the facility. Data-driven influent predictions as part of the digital twin functionality allow predicting plant performance up to five days into the future (wastewater forecast) and evaluating various operational scenarios. Digital twins can help improve the performance of a water facility, providing considerable potential savings from better process automation, online optimization, fault detection, maintenance, and more proactive operation. The computation speed and the model complexity for predictions within 24 hours are some challenges to overcome. Establishing protocols based on good practices is necessary to support digital twin implementation (IWA, 2021). Similarly, knowledge and methods for transitioning to a circular economy are only emerging (Blomsma et al., 2019), and the concept needs action and validation.

1.4.3 Enabling circularity in the water sector through real-life experimentation

The CE model is relatively new for businesses, citizens, and local/central governments. Changing to a sustainable or circular model includes clear societal and environmental goals, focusing on resource loops (Geissdoerfer et al., 2017), and experimentation is required to trial the viability of options in a real-life context and initiate transitions within organizations (Bocken, 2021). Experimenting in the early stages of innovation will benefit organizations by preventing flawed idea-generation processes that may influence the ability of organizations to break the status quo (Bocken, 2017). Experimentation can kick-start transitions by demonstrating the potential of circular solutions in practice and starting change processes (Bocken et al., 2018).

The transition to a circular economy presents an opportunity to accelerate and scale up scientific and technological developments supporting greater efficiency in the water sector. Therefore, establishing experimental ecosystems can facilitate the demonstration of innovations. An ecosystem innovation looks at the interaction among the different levels (product/service, business models, ecosystem) and stakeholders to develop co-specialized complementary products/services to maximize value by exploring combined benefits (Stahel, 2008).

Considering the discussion in the previous sections, the circular economy solutions in the water sector are also searching for validation. The intersection between resource flow strategies (Fig. 1.1b) combined with the different circular frameworks applied to the water sector (Fig. 1.1a) and digital technologies represented by the strategy reconnect (Fig. 1.1c) provides an innovative new approach that needs validation. Different frameworks as the one proposed, can be explored by implementing living labs (Fig. 1.1). In this sense, implementing a collaborative ecosystem for community-driven innovations in a multi-stakeholder context, such as a Living Lab, offers an effective research methodology for sensing, prototyping, validating, and refining innovative solutions in multiple and evolving real-life contexts (Eriksson et al., 2005). Adapted to the water sector, Water Oriented Living Labs (WOLLs) are an instrument in modern innovation for enabling the co-creation of innovations (Fig. 1.1).

Figure 1.1 Interconnection between water strategies, business models, and digital technologies. (Adapted from: (A) Circular Economy Alliance (2022); (B) Konietzko et al. (2020); (C) CE-IoT project (2022); (D) Water Europe a and b.)

A WOLL is a real-life demonstration and implementation instrument that brings together public and private institutions, government, civil society, and academia to build structured grounds jointly. The main focus is to develop, validate, and scale-up innovations that embrace new technologies, governance, business models, and advancing innovative policies to achieve a Water-Smart Society (Water Europe, 2022a). WOLLs considers digital twins implementation a vital function in creating living digital replicas that can provide an integrated digital knowledge management system to share up-to-date information with supervisors, water managers, and citizens (Water Europe, 2022b). The interaction among users, private and public organisations, research institutions, etc., allows the creation of new products or services in physical or virtual settings, replicating realistic situations (Bergvall-Kåreborn et al., 2009). A living lab aims to directly integrate customers and other stakeholders to reduce new product development risks. In combination with scientific evaluation methods, direct customer feedback will influence a more reliable market evaluation, significantly reducing technology and business risks (Water Europe, 2022a).

Therefore, implementing a harmonized approach through WOLLs to develop circular water solutions can accelerate innovation to tackle critical societal challenges such as water scarcity, pollution, and climate change (Water Europe, 2022b). A water-smart society needs significant societal changes in response to climate change and demographic trends, including realizing a robust and reliable water sector with flood risk management and water security as essential goals. It is essential to demonstrate that innovations are reliable, work well at a large scale, and are sustainable at a system level, improving overall environmental benefits. Implementing a holistic approach, including circular strategies and digital technologies through real-life demonstrators, can support the validation and scale of circular water solutions.

1.5 Conclusions

The circular economy is a promising initiative toward sustainable development, and circular solutions should consider a multidisciplinary approach for successful implementation. In the present study, a holistic approach suggests a broader overview of implementing circularity in the water sector by considering the interaction between the circular strategies adapted to water activities, circular business model strategies, and digital technologies.

In the literature, the different frameworks for circular economy in the water sector cover the strategies of avoiding, replacing, reducing, reusing, recycling, cascading, storing, removing, replenishing, re-optimize, and recovering, covering an extensive range of water solutions. Mapping the water strategies to the five circular business model strategies based on resource flows (narrow, close, slow, regenerate, and inform) allowed us to identify the need to include more explicitly the use of digital technologies in the development of circular water solutions. Therefore, a proposition is to add another strategy called reconnect that represents the use of new technologies. Including digital technologies to manage combined solutions in water utilities supported by data-driven models will optimize costs by improving operations. Commercial opportunities arise from implementing circular strategies and business models to reveal the water value and create value-centered jobs and businesses.

Nevertheless, the circular economy is an emerging economic model that needs validation. In this sense, to validate circular solutions, implementing experimental environments such as WOLLs will help to test innovations and facilitate the adoption of circular solutions. Water-oriented living labs approach can provide a unified approach to promote the co-creation, testing, prototyping, validating, refining, and evaluating of innovative solutions in representative real-life environments, with the ultimate aim of realizing a Water-Smart Society. Demonstrating circular water solutions will allow a better understanding of innovations to validate and replicate successful practices in different environmental, social, and cultural