Urban Water Systems Research Articles

Can Tanker Water Services Contribute to Sustainable Access to Water? A Systematic Review of Case Studies in Urban Areas

Tanker water markets (TWM) supply water services in many urban areas, including those unconnected to public infrastructures. Notwithstanding, they have been associated with outcomes in conflict with sustainability goals of water policy, e.g., through inequitable and unaffordable supply or by contributing to groundwater overexploitation. So far, the literature dedicated to TWM has primarily conducted case studies embedded in diverse local contexts, which impedes the comparison and transfer of insights. In this article, we systematically summarize existing empirical knowledge on TWM and assess to what extent normative claims about the impacts of TWM on sustainability goals are supported by evidence. We use the concept of sustainable access, which combines notions of what constitutes access to water and what characterizes sustainable supply of services. The available evidence suggests that TWM have two key functions in urban water systems: (1) They provide services at otherwise unavailable levels, particularly with respect to the temporal availability and spatial accessibility of the service, and (2) they extend access to areas without or with low-quality network supply, typically low-income communities on the fringe of cities. From the perspective of sustainable access, we find that TWM can provide high service levels and thus fill a specific gap in the landscape of urban water services. Due to comparatively high prices, however, it is unlikely that these services are affordable for all. The combination of heterogeneous access to cheaper (subsidized) piped water and marginal pricing in TWM results in allocation outcomes that are not coherent with existing notions of equitable access to water. However, there is little convincing evidence that TWM necessarily result in unsustainable water use. The literature indicates that urban water governance in the studied areas is frequently characterized by a lack of effective institutions, which impedes the regulation or formalization of TWM.

Adoption of water reuse technologies: An assessment under different regulatory and operational scenarios

Water reuse technologies may alleviate the water scarcity problems that affect many world regions, but their adoption is still limited. In particular, key actors in the adoption of water reuse technologies are water utilities, that provide both urban water and wastewater treatment services. Water utilities are embedded in the urban water system, which includes several stakeholders (urban water users, citizens at large, the environment) that may drive or pose barriers to water reuse adoption. Therefore, to ensure a smooth introduction of water reuse technologies, it is fundamental to understand how water reuse interacts with the existing urban water system and impacts its stakeholders. This paper contributes to the ongoing debate on water reuse by conceptualizing the interaction between water reuse technologies and the urban water system and its stakeholders, and addressing the adoption decision of water utilities by assessing its economic and environmental consequences. Based on a review of literature, policy and other secondary documents, and on primary data coming from interviews with experts from a water utility operating in Southern Italy, the study models the utility's response to a shift from urban to reuse water. It then simulates how reuse water introduction impacts on the utility and other stakeholders of the water system, under various regulatory and operational scenarios defined through a thorough analysis of policy documents and literature. Results show that the adoption of water reuse reduces the utility's margin by cannibalizing urban water demand, but appropriate policy measures may enhance the economic sustainability of reuse. System-level performances, such as impact on freshwater savings, costs for users, effects on the public budget, are also assessed, showing how different regulatory options moderate the intensity of impacts for the different stakeholders of the water system. Furthermore, the adoption of reuse water by the most distant users is found to enhance the economic sustainability of reuse and positively impact the utility's margin.

Fairmount Water Works and its Water Stories

The Fairmount Water Works of Philadelphia has many stories to tell that span its rich 200-year history. It speaks to the history of technology in America, urban water systems, public health and civic architecture. Although struggling with the increasing impact of climate change, it still has a significant role to play today as a heritage site and as an iconic expression of architectural beauty, civic pride, environmental education and protection and the stewardship of water for all.

Integrated asset management of urban water and wastewater systems

AbstractThis paper presents a decision support system for the integrated management of water distribution and wastewater collection networks. The proposed methodology utilizes system dynamics to integrate water mains and sewers with finance and sociopolitical sectors. It enables user rate‐setting and planning of integrated water and wastewater infrastructure operational and capital works over their life‐cycle (50+ years). The integrated asset management model is implemented using data from a large‐sized utility in Southern Ontario, Canada. The result indicates that the integrated framework enables the utility to accelerate funding for capital and operational works due to the integration of the water and wastewater financial resources and improve the integrated levels of service. In practice, the proposed integrated framework empowers and encourages water utilities to manage and plan their assets in an integrated approach to enhance their water and wastewater assets' infrastructure, financial, and sociopolitical performance relative to managing them in isolation.

Capacity development for water reuse in in-formal partnerships in northern Namibia

In central northern Namibia, challenges in water governance related to scarcity meet needs in capacity development on municipal levels. Reuse of treated water in agriculture forms a technical innovation in urbanizing arid regions, because it potentially contributes to both improving water availability and reducing pollution from waste water in arid regions. Governing this transformative approach entails a complexity of processes and actors at different levels and in a range of sectors. The aim of this research is to assess the potential of an informal municipal partnership to (a) support capacity development in implementation of innovation in urban water systems (here: water reuse), and (b) compensate for lack of coordination in governance. Establishing a municipal partnership for wastewater treatment was part of a living lab approach analyzing the potential for water reuse, in collaboration of an interdisciplinary team of researchers, municipal decision-makers, engineers and farmers. Findings show the potential and limitations in capacity development in municipal water governance by means of an informal partnership. The lessons learnt on establishing an informal municipal partnership for learning and capacity development in water governance provide valuable insights for water governance in both research and practice, in particular but not limited to the field of water reuse as means of transforming socio-hydrological relations toward sustainability. The research thus contributes to research on water reuse governance, and to transformative research on water in social-ecological systems.

Assessment of the impact of urban water system scheduling on urban flooding by using coupled hydrological and hydrodynamic model in Fuzhou City, China

With climate change and urbanization development, urban areas are facing more serious floods. As a result, hydrological and hydrodynamic models have recently shown a broad application prospect in urban flood simulating and forecasting. For the area with rich inland rivers, urban water resources can be effectively regulated and redistributed through river networks and hydraulic structures scheduling. However, the lack of research on the effect of scheduling becomes a major limitation in model applications. Based on a coupled hydrodynamics model, the current study simulates the flooding response to the combined rainstorm and scheduling scenarios and analyzes the river overflow at the community scale. The result indicated that three local regions in the Jin'an study area are inundated easily. The locations near Qinting Lake were more sensitive to the water regulation rules than others. In the model of control on Qinting Lake, section A is more sensitive to the schedule control than section B, while for section A, the water level increased by 1.44% under the return period (RP) (10 a), and the rate changed to 2.64% under the RP (100 a). The differences in inundation from various scenarios are relatively small. In the mode of joint discharge rules under RP (50 a), the water level changed by 4.77% in section A and 1.24% in section B. The simulation at the community scale considers the overflow process, and the results indicated that the total inundation area decreased by 12.8 ha under joint schedules. The significant effects to alleviate urban inundation mainly come from the decreased flood overflow from the channel, but not from the flooding nodes. This study provides promising references for urban flood management.

Virulence markers, adhesion and biofilm formation of Escherichia coli strains isolated from drinking water supplies of north Paraná State, Brazil.

Waterborne diseases are a major public health problem responsible for a high number of deaths worldwide, of which Escherichia coli is a major agent of contamination. This study investigates the occurrence of different diarrheagenic E. coli (DEC) pathotypes and its relationship with adherence patterns and biofilm formation. Between 2012 and 2014, a total of 1,780 drinking water samples were collected from different rural communities and urban water systems of north Paraná State. A total of 14% were positive for E. coli and 250 non-duplicate E. coli isolates were obtained. Between the E. coli isolates, 28 (11.2%) harbored DEC-associated genes, 10.7% being classified as Shiga toxin-producing E. coli (STEC), 64.3% enteroaggregative E. coli (EAEC) and 25% atypical enteropathogenic E. coli (aEPEC). The aggregative adherence (AA) was the predominant adherence pattern (84%), significantly associated with biofilm formation (p < 0.0001). On the other hand, the AA pattern and biofilm formation were not significantly associated to DEC pathotypes (p > 0.05). Therefore, we proposed that the AA pattern and biofilm formation in E. coli isolated from drinking water supplies could be associated with adherence and colonization of abiotic surfaces, such as pipes, leading to persistence and resistance to treatment or disinfection.

Human exposure to microplastics from urban decentralized pay-to-fetch drinking-water refill kiosks

Microplastics in the human diet have become a worldwide concern. To date, microplastics in urban drinking water supplies, such as decentralized drinking-water refill kiosks, have not been studied and are a pressing concern since they are so closely tied to human life and have a significant influence on health. This study evaluated the occurrence and characteristics of microplastics in 63 drinking water samples collected from decentralized refill kiosks in the Mexico City metropolitan area. All of the sampled drinking water contained microplastics in concentrations ranging from 11 to 860 microplastics L−1. The detected microplastics were mostly fiber (65 %), followed by fragment (28 %), and film (7 %). They were mainly composed of polyethylene terephthalate, polyamides, vinyl polymers, polyacetal, and cellophane in sizes ranging from 20 μm to 5 mm, with 75 % of them accounting for sizes <300 μm. SEM-EDX analysis revealed weathered microplastics, biota adherence, and the presence of inorganic elements on the surface of microplastics. We estimate that Mexico City residents inadvertently ingest 42 microplastics L−1, with an annual exposure of around 1.47 × 104 microplastics per adult and 6.73 × 103 microplastics per child. Therefore, future research is needed to strengthen drinking water refill kiosk guidelines and standards for better microplastic management. This study serves as a wake-up call to many developing countries that use similar urban water systems, drawing their attention to global microplastic contamination of drinking water.

Delivering Blue-Green Infrastructure: Innovation Pathways for Integrating Multiple Values

Realizing a multifunctional blue-green infrastructure (BGI) as a nature-based solution for the urban water system and built environment within crowded city areas is seen as a promising route for the process of climate adaptation. BGI projects like rain gardens, green roofs, and water squares can be combined to achieve a variety of technical (drainage), environmental (biodiversity), economic (property development) and social (health and wellbeing) goals and values at a local neighborhood level. As integrating such values within local governments' existing fragmented structures and procedures has proved to be challenging, urban governments are increasingly experimenting with innovative governance approaches at different levels to capitalize on the multiple benefits of BGI. Nevertheless, policy actors who try to justify their choices in the face of value conflicts are both constrained and enabled by the institutions they can call on. Using a qualitative comparative case study, this article therefore aims to gain insight into different ways of, or approaches to, organizing value integration. In particular, we compare: (1) a top-down case of programmatic steering to translate value integration into a neighborhood approach; (2) a market-oriented innovative procurement approach to local public-private partnership projects; and (3) a case of invitational governance for a future-proof neighborhood that is striving for a sense of citizen ownership. Our findings demonstrate the conditions, drivers, and barriers to the value integration of different governance innovations in relation to time-related issues, the types of support available, organizational embedding, and stakeholder involvement. Our specific focus is on understanding how social and sustainability and spatial and technical values are integrated. This paper thus helps us to get to grips with different pathways to value integration in the context of urban infrastructures, as well as their applicability and the conditions for success. These insights will enable the further strengthening of our capacity to build climate-proof cities in a value-driven and integrative manner.

Integration of multi-objective spatial optimization and data-driven interpretation to direct the city-wide sustainable promotion of building-based decentralized water technologies

Decentralized water technologies such as rainwater harvesting (RWH) and greywater recycling (GWR) can supplement centralized urban water systems, helping reduce water withdrawal and improve water reliability. These benefits only emerge when decentralized water technologies are widely implemented. Several decision-supporting frameworks have been developed to identify suitable locations for deploying decentralized water technologies in a city. Yet, the support remains inadequate regarding: (1) the evaluation of the trade-off between environmental benefits and economic costs in selecting locations, and (2) the interpretation of the transition of optimal selections from low to high investment to assist in the promotion. This study presents an integrated analytic framework that combines multi-objective optimization and data-driven interpretation to direct the city-wide sustainable promotion of building-based decentralized water technologies. We select single-family houses in the city of Boston and apply the framework to study the promotion of building-based RWH and GWR. The framework starts with multi-objective spatial optimization to identify the non-dominant optimal selections (i.e., Pareto-front) of houses and technologies at the trade-off between maximizing energy savings and minimizing financial investment. Then, we evaluate the impact of the initial selection setting and the community-based maximum water saving constraint on the Pareto-optimal front. The spatial optimization shows that RWH is much more applicable than GWR for single-family house communities in Boston. When interpreting the Pareto-front, two clusters of census blocks stand out based on the change in the percentages of houses selected to invest RWH and GWR in each census block along with different investment levels. One cluster demonstrates its priority of being first selected to deploy RWH. Using Random Forest, critical features explain why one cluster should be selected first for promotion, including the larger demand for non-potable water use, longer distance from the centralized facilities, and larger rooftop for collecting rainwater. Finally, we discuss possible future improvements of the proposed spatial optimization and interpretation framework. Overall, our study can be useful to promote decentralized water technologies in cities.

Sponge City Design Based on Intelligent Displacement Optimization

The concept of sponge city urbanization construction is the important guiding idea, to quickly eliminate the end drainage characteristics of the traditional urban drainage system; the effect is very poor under the actual extreme precipitation weather conditions. The failure of the drainage system will cause urban waterlogging and even sewage overflow, thus causing the collapse of the entire urban water system. In a variety of heavy precipitation weather frequency as the background, this paper first makes a detailed introduction about the concept of sponge city, mainly describes the features and functionality of the sponge city, compares them and the function of traditional urban drainage system, and finds out the advantages and disadvantages of the sponge city on the function, especially on the end of the drainage function, which is even better than traditional drainage system. Finally, through modern computer intelligence technology, the artificial neural network is combined with the sponge city drainage system, and the influence of rainfall prediction module and centralized coordinated optimization sponge processing module on the urban drainage is added on the basis of the traditional drainage system. As a reliable idea to solve the sponge bottom problem with weak urban drainage function, the feasibility of this idea is proved theoretically.

Emerging electrochemical techniques for identifying and removing micro/nanoplastics in urban waters

The ubiquitous micro/nanoplastics (MPs/NPs) in urban waters are priority pollutants due to their toxic effects on living organisms. Currently, great efforts have been made to realize a plastic-free urban water system, and the identification and removal of MPs/NPs are two primary issues. Among diverse methods, emerging electrochemical techniques have gained growing interests owing to their facile implementation, high efficiency, eco-compatibility, onsite operation, etc. Herein, recent progress in the electrochemical identification and removal of MPs/NPs in urban waters are comprehensively reviewed. The electrochemical sensing of MPs/NPs and their released pollutants (e.g., bisphenol A (BPA)) has been analyzed, and the sensing principles and the featured electrochemical devices/electrodes are examined. Afterwards, recent applications of electrochemical methods (i.e., electrocoagulation, electroadsorption, electrokinetic separation and electrochemical degradation) in MPs/NPs removal are discussed in detail. The influences of critical parameters (e.g., plastics' property, current density and electrolyte) in the electrochemical identification and removal of MPs/NPs are also analyzed. Finally, the current challenges and prospects in electrochemical sensing and removal of MPs/NPs in urban waters are elaborated. This review would advance efficient electrochemical technologies for future MPs/NPs pollutions management in urban waters.

Removal of microplastics and nanoplastics from urban waters: Separation and degradation

The omnipresent micro/nanoplastics (MPs/NPs) in urban waters arouse great public concern. To build a MP/NP-free urban water system, enormous efforts have been made to meet this goal via separating and degrading MPs/NPs in urban waters. Herein, we comprehensively review the recent developments in the separation and degradation of MPs/NPs in urban waters. Efficient MP/NP separation techniques, such as adsorption, coagulation/flocculation, flotation, filtration, and magnetic separation are first summarized. The influence of functional materials/reagents, properties of MPs/NPs, and aquatic chemistry on the separation efficiency is analyzed. Then, MP/NP degradation methods, including electrochemical degradation, advanced oxidation processes (AOPs), photodegradation, photocatalytic degradation, and biological degradation are detailed. Also, the effects of critical functional materials/organisms and operational parameters on degradation performance are discussed. At last, the current challenges and prospects in the separation, degradation, and further upcycling of MPs/NPs in urban waters are outlined. This review will potentially guide the development of next-generation technologies for MP/NP pollution control in urban waters.

Challenges, drivers, and benefits to integrated infrastructure management of water, wastewater, stormwater and transportation systems

Infrastructure systems are known to be interdependent systems; however, infrastructure systems are typically managed individually by agencies in charge of these systems. The existing literature has proposed the concept of an integrated infrastructure management approach, yet this literature has focused on managing infrastructure systems in short-term contexts (e.g., response to natural and human-made disasters). As such, limited understanding exists about implementing an integrated infrastructure management approach in the long-term (i.e., maintenance and rehabilitation). This study aims to explore the challenges, drivers, and benefits of implementing an integrated urban infrastructure management approach by agencies managing urban water, wastewater, stormwater, and transportation infrastructure systems in the long-term. This study qualitatively analyzed 15 semi-structured interviews with stakeholders in the management of infrastructure systems in Chile. It was found that the implementation of an integrated infrastructure management approach is challenged and driven by organizational instead of technical aspects. It was found that the local context where agencies operate represents a challenge for the successful implementation, the willingness to collaborate of infrastructure agencies’ workers represents a driver to implementation, and that benefits encompass agencies and users. Infrastructure agencies can use our findings to account for contextual conditions to successfully implement an integrated infrastructure management approach.

Toward Carbon-Neutral Water Systems: Insights from Global Cities

Many cities have pledged to achieve carbon neutrality. The urban water industry can also contribute its share to a carbon-neutral future. Using a multi-city time-series analysis approach, this study aims to assess the progress and lessons learned from the greenhouse gas (GHG) emissions management of urban water systems in four global cities: Amsterdam, Melbourne, New York City, and Tokyo. These cities are advanced in setting GHG emissions reduction targets and reporting GHG emissions in their water industries. All four cities have reduced the GHG emissions in their water industries, compared with those from more than a decade ago (i.e., the latest three-year moving averages are 13%–32% lower), although the emissions have “rebounded” multiple times over the years. The emissions reductions were mainly due to various engineering opportunities such as solar and mini-hydro power generation, biogas valorization, sludge digestion and incineration optimization, and aeration system optimization. These cities have recognized the many challenges in reaching carbon-neutrality goals, which include fluctuating water demand and rainfall, more carbon-intensive flood-prevention and water-supply strategies, meeting new air and water quality standards, and revising GHG emissions accounting methods. This study has also shown that it is difficult for the water industry to achieve carbon neutrality on its own. A collaborative approach with other sectors is needed when aiming toward the city’s carbon-neutrality goal. Such an approach involves expanding the usual system boundary of the water industry to externally tap into both engineering and non-engineering opportunities.

Towards water resilience through Nature‐based Solutions in the Global South? Scoping the prevailing conditions for Water Sensitive Design in Cape Town and Johannesburg

Water Sensitive Design (WSD) is gaining attention as a Nature-based Solution (NbS) to urban water problems. It incorporates green infrastructure with engineered urban water systems through innovative design of the built environment and urban landscape. In Africa, Johannesburg and Cape Town are two cities engaging with WSD at a policy level. This paper uses the Strategic Niche Management (SNM) approach in a comparative analysis of ongoing engagement with WSD in Johannesburg and Cape Town. We explore the extent to which this engagement signals the launch of the transition towards water resilience. WSD represents a niche that is in synergy with the visions of sustainable urban (water and environmental) management in both cities. Results indicate a progressive engagement with WSD by different actors at regime and niche levels. However, the lack of coordination and capacity deficiencies due to limited social networks and higher order learning are challenges that constrain take-off and further consolidation of the WSD approach in the transition towards water resilient futures. Furthermore, we find urban governance practitioners struggle with reconciling the pursuit of visions of sustainability to be realised through nature-based urban development with the pressing infrastructure deficits that persist in most African cities.

The Readiness of the Water Utilities in Bulgaria for Transition toward a Circular Economy

Urban water systems are still in their infancy regarding the transition toward a circular economy, despite the sporadic successful examples worldwide. This paper was aimed at analyzing the preparedness of four water utilities in Bulgaria for the implementation of circular economy principles and solutions. These utilities provide water supply and sewerage services to about 30% of the population in Bulgaria. SWOT analysis was used as a core tool. Publicly available data such as nonrevenue water, pressure management, energy demand, network digitalization, and sludge utilization were used to explore the internal factors. The external environment was considered through the legislative and socioeconomic framework, climate change, etc. Finally, the credibility of the conclusions was verified in workshops with the water utilities. The key positive outcomes were that the external factors favor the shift to circular systems, while the major weakness, i.e., the aged infrastructure, is actually a good opportunity for the implementation of modern and circular solutions. The efficient collaboration of water utilities with other actors is a precondition for the development of a sustainable market for “circular” products.

Implementing machine learning to optimize the cost-benefit of urban water clarifier geometrics

Clarification basins are ubiquitous water treatment units applied across urban water systems. Diverse applications include stormwater systems, stabilization lagoons, equalization, storage and green infrastructure. Residence time (RT), surface overflow rate (SOR) and the Storm Water Management Model (SWMM) are readily implemented but are not formulated to optimize basin geometrics because transport dynamics remain unresolved. As a result, basin design yields high costs from hundreds of thousands to tens of million USD. Basin optimization and retrofits can benefit from more robust and efficient tools. More advanced methods such as computational fluid dynamics (CFD), while demonstrating benefits for resolving transport, can be complex and computationally expensive for routine applications. To provide stakeholders with an efficient and robust tool, this study develops a novel optimization framework for basin geometrics with machine learning (ML). This framework (1) leverages high-performance computing (HPC) and the predictive capability of CFD to provide artificial neural network (ANN) development and (2) integrates a trained ANN model with a hybrid evolutionary-gradient-based optimization algorithm through the ANN automatic differentiation (AD) functionality. ANN model results for particulate matter (PM) clarification demonstrate high predictive capability with a coefficient of determination (R2) of 0.998 on the test dataset. The ANN model for total PM clarification of three (3) heterodisperse particle size distributions (PSDs) also illustrates good performance (R2>0.986). The proposed framework was implemented for a basin and watershed loading conditions in Florida (USA), the ML basin designs yield substantially improved cost-effectiveness compared to common designs (square and circular basins) and RT-based design for all PSDs tested. To meet a presumptive regulatory criteria of 80% PM separation (widely adopted in the USA), the ML framework yields 4.7X to 8X lower cost than the common basin designs tested. Compared to the RT-based design, the ML design yields 5.6X to 83.5X cost reduction as a function of the finer, medium, and coarser PSDs. Furthermore, the proposed framework benefits from ANN’s high computational efficiency. Optimization of basin geometrics is performed in minutes on a laptop using the framework. The framework is a promising adjuvant tool for cost-effective and sustainable basin implementation across urban water systems.

Evaluation of urban water systems through ‘stream-user-city’ interactions: The example of Izmir Meles Stream

Evaluation of urban water systems through ‘stream-user-city’ interactions: The example of Izmir Meles Stream

Evaluation and promotion strategy of resilience of urban water supply system under flood and drought disasters.

With global climate change and the rapid urbanization, urban flood and drought disasters are frequent and urban water supply systems are facing a sea of serious challenges. It is crucial to assess the resilience of urban water supply systems and develop corresponding disaster mitigation and improvement strategies. Urban water supply systems include many subsystems, but existing researches generally focus on a single subsystem. Therefore, this paper proposes a correlation analysis method and a factor analysis method for the resilience evaluation index system of urban water supply systems by combining each subsystem and applying grey system theory. The method can reflect the four dimensions of the water supply process (water source, water plant, supply and distribution network and users) and the five dimensions of the urban management system (society, natural environment, economy, physics and organization). Taking Qingdao as an example, a multi-level integrated evaluation model based on a cloud model is applied to simulate and analyze the resilience of Qingdao's water supply system. As a result, decision support is provided for planning and building resilience systems for urban water systems in the short and long term, based on four main factors.