Sustainable and Resilient Urban Water Systems: The Role of Decentralization and Planning

Revisiting the concept, urban practices, current advances, and future prospects of green infrastructure

The inevitable increase in the human population's reliance on natural resources necessitates practical, and result-oriented solutions and strategies to enhance human's standard of living while minimizing its impact on essential resources. The global water resource depletion has spurred discourse among key international stakeholder in uniting efforts to achieve sustainability. For decades, the application of a combination of key strategies which relies on designing cities to promote the sustainable use of water and water resources have received global endorsement. The roadmap towards designing water-wise infrastructure in urban areas has derived from preexisting water conservation schemes. Green infrastructure (GI) is based on the key principle of the harmonious integration of natural elements and ecological processes to sustainably conserve natural resources. This paper aims to analyze and assess the development of sustainable and effective solutions for urban water quality management, by providing a comprehensive review of the concept of GI. We further digest the components and strategies of GI, its historical evolution, the rate of adoption and application on a regional scale and future prospects. GI with continued innovation and refinement, holds immense potential to mitigate the detrimental effects of urbanization on water resources and promote sustainable urban water management.

The development of resilience research in critical infrastructure systems: A bibliometric perspective

Critical infrastructure systems (CISs) are the cornerstone of modern cities. Substantial economic losses and social impacts are caused once natural disasters or man-made disruptions attack the CISs. As a "resilient city" has become an essential theme of communities' sustainable development, research on resilience and its practice in industries boost the CISs' capacity to respond and adapt to changing environments. From the Web of Science (WOS) Core Collection, this study screened 1,247 scientific articles related to resilience in CISs and conducted a bibliometric analysis to investigate the evolution and future potential in this field. Topic visualized networks were constructed for CIS resilience using CiteSpace, a dedicated tool for visualizing and analyzing trends and patterns in scientific literature. The results demonstrate collaborative research networks among countries, institutions, main scholar/group networks, and leading journals publishing CIS resilience work. This study also explained how the research interest evolved over the last 20 years and found the current frontiers pointing to "power systems resilience" and "supply chain resilience." The reasons were discussed subsequently from the perspectives of the influence that natural hazards (based on the EM-DAT data) and government policies have upon CISs' resilience work.

More Than a Service: Values of Rivers, Wetlands and Floodplains Are Informed by Both Function and Feeling

How people value rivers, wetlands and floodplains influences their attitudes, beliefs and behaviours towards these ecosystems, and can shape policy and management interventions. Better understanding why people value rivers, wetlands and floodplains and their key ecosystem components, such as vegetation, helps to determine what factors underpin the social legitimacy required for effective management of these systems. This study sought to ascertain perspectives on the value of non-woody vegetation in river-floodplain systems via an online survey. The survey found that participants valued non-woody vegetation for their provision of a range of ecosystem functions and services, with strong emphasis on ecological aspects such as regulation functions, habitat provision and biodiversity. However, the inclusion of a question framed to focus on stories or narratives resulted in a different emphasis. Responses indicated that non-woody vegetation, and rivers, wetlands and floodplains were valued for the way they made people feel through lived experiences such as recreational activities, personal interactions with nature, educational and research experiences. This highlights the important role of storytelling in navigating complex natural resource management challenges and ascertaining a deeper understanding of values that moves beyond provision of function to feeling. Improved understanding of the diverse ways people value and interact with river-floodplain systems will help develop narratives and forms of engagement that foster shared understanding, empathy and collaboration. Appreciation of plural values such as the provision of functions and services along with the role of emotional connections and lived experience will likely increase lasting engagement of the general public with management to protect and restore river-floodplain systems.

Greywater reuse as a key enabler for improving urban wastewater management

Sustainable water management is essential to guaranteeing access to safe water and addressing the challenges posed by climate change, urbanization, and population growth. In a typical household, greywater, which includes everything but toilet waste, constitutes 50-80% of daily wastewater generation and is characterized by low organic strength and high volume. This can be an issue for large urban wastewater treatment plants designed for high-strength operations. Segregation of greywater at the source for decentralized wastewater treatment is therefore necessary for its proper management using separate treatment strategies. Greywater reuse may thus lead to increased resilience and adaptability of local water systems, reduction in transport costs, and achievement of fit-for-purpose reuse. After covering greywater characteristics, we present an overview of existing and upcoming technologies for greywater treatment. Biological treatment technologies, such as nature-based technologies, biofilm technologies, and membrane bioreactors (MBR), conjugate with physicochemical treatment methods, such as membrane filtration, sorption and ion exchange technologies, and ultraviolet (UV) disinfection, may be able to produce treated water within the allowable parameters for reuse. We also provide a novel way to tackle challenges like the demographic variance of greywater quality, lack of a legal framework for greywater management, monitoring and control systems, and the consumer perspective on greywater reuse. Finally, benefits, such as the potential water and energy savings and sustainable future of greywater reuse in an urban context, are discussed.

Creating an indicator system for the United Nations Sustainable Development Goals in communities and municipalities: Application and analysis in an Austrian case study

Sustainability indicators should implement the United Nations Sustainable Development Goals (UN SDGs). Indicators in literature often consider large sets of actions and are thus complex in application. Therefore, this work derives energy- and resource-related SDG indicators for communities and municipalities with low complexity. Moreover, this work analyzes three different policy paths to promote SDG contribution. The policy paths consider SDG target settings and two different incentive schemes in the form of penalties and investment subsidies. The indicators and policy actions are applied in two case studies for communities and municipalities in Austria. Therefore, an optimization model that considers the case study setups, SDG targets and policy actions is developed. The modeling approach shows applicability and positive contribution to sustainable development by indicators. Moreover, the results show the applicability of the three policy paths. Implementing the target-setting path directly leads to the desired SDG targets and provides insights into the costs for target achievement. The incentive scheme paths also lead to selected targets, but they require a cost assessment of the provided incentive schemes. A combination of both incentive schemes leads to the lowest costs. However, policymakers should implement a workflow that considers all three policy paths for policy action settings.

Wastewater reuse and energy saving require a more decentralized urban wastewater system? Evidence from multi-objective optimal design at the city scale

Decentralization is recognized as an emerging solution for a more sustainable urban wastewater system (UWS) for the future. However, the debate of centralization vs. decentralization at the system's planning stage remains unresolved, mainly due to the complexity of the system's spatial structure and the multiple design objectives, such as water reuse and energy conservation. This paper presents the Sustainable Urban Wastewater System Generator (SUWStor) as a tool to address this issue. Integrating a graph representation of the system structure and the ant colony algorithm, SUWStor can produce Pareto optimal solutions for system design under three objectives: minimizing the capital cost, minimizing the operational energy consumption, and maximizing the water reuse capacity. The model is used for system design in a 100-square-km new city, the Xiong'an New District in China. Compared to the solution based on human experience, the model can reduce the system's capital cost by 7% and the operational energy in the pipe network by 26%, while maintaining the water reuse capacity at 100%. With this model, the relation between the optimal system layout and the choice over different design objectives can be discussed for any given area. In our case study, the optimal capacity of WWTPs for the lowest-cost solution is 48,000 m³ per day, leading to a total number of WWTPs of 5. As the water reuse level increases to maximum, the optimal capacity reduces to 15,000 m³ per day, where the number of WWTPs is 16. The model is also able to perform significantly better than the locally optimized results, in which only the WWTP locations are fixed at their optimal values. This demonstrates the importance of a global optimization model in designing the integrated UWS.

Comparison of MBR and MBBR followed by UV or electrochemical disinfection for decentralized greywater treatment

Greywater is an attractive source for water reuse at the household or building level, particularly for non-potable applications. Two greywater treatment approaches are membrane bioreactors (MBR) and moving bed biofilm reactors (MBBR), yet, their performance has not been compared so far within their respective treatment flowsheets, including post-disinfection. Two lab-scale treatment trains were operated on synthetic greywater: a) MBR with either polymeric (chlorinated polyethylene, C-PE, 165 days) or ceramic (silicon carbide, SiC, 199 days) membranes coupled with UV disinfection; and b) single-stage (66 days) or two-stage (124 days) MBBR coupled with an electrochemical cell (EC) for in-situ disinfectant generation. Water quality was constantly monitored, and Escherichia coli log removals were assessed through spike tests. Under low-flux operation of the MBR (<8 L·m ^- 2·h ^- 1), the SiC membranes delayed the onset of membrane fouling and needed less frequent cleaning compared to C-PE membranes. Both treatment systems met most water quality requirements for unrestricted greywater reuse, at a 10-fold lower reactor volume for the MBR than the MBBR. However, neither the MBR nor the two-staged MBBR allowed adequate nitrogen removal, and the MBBR did not consistently meet effluent chemical oxygen demand and turbidity requirements. Both EC and UV provided non-detectable E. coli concentrations in the effluent. Although the EC provided residual disinfection, scaling and fouling decreased its energetic and disinfection performance over time, making it less efficient than UV disinfection. Several outlines to improve the performance of both treatment trains and disinfection processes are proposed, thus, allowing a fit-for-use approach that leverages the advantages of the respective treatment trains. Results from this investigation will assist in elucidating the most efficient, robust, and low-maintenance technology and configurations for small-scale greywater treatment for reuse.

Breaking water carbon nexus by the natural biological system: ultimate solution for ESG challenges

Clean water supply has become an enormous challenge in pursuance of the global warming process. Water technologies have traditionally created carbon emissions and chemical reactions that pollute the landscape, aquifers, and the air. The need for carbon footprint reduction and corporate ESG consideration has led to adopt a more environmentally friendly water treatment and management system. The Natural Biological System (NBS) is a nature-based technology for sewage and waste stream treatment and management, rehabilitating affected water bodies, reducing greenhouse gas (GHG) emissions, and rebalancing eco-systems. The NBS is a patent-tailored solution with the ability of large-scale water treatment and a negative carbon footprint promoting the user ESG rating. From Chile to India, the NBS is changing the global water-energy equation, reducing dependence on energy and maintenance, freeing up valuable water resources for on-site usage, and restoring nature's ability to preserve and protect itself and to stop the escalating climate change effects.

Sustaining the urban commons in Ghana through decentralized planning

With global urbanization on the increase and cities now hosting more than half of the planet's population, there are concerns regarding the protection of urban commons as part of sustainability efforts, especially in sub-Saharan Africa. Decentralized urban planning is a policy tool and practice that is used to organize urban infrastructure for sustainable development. Yet, how it can be used to sustain the urban commons remains fragmented in the literature. This study reviews and synthesizes urban planning and urban commons literature using the Institutional Analysis and Development Framework and the non-cooperative game theory to identify how urban planning can protect and sustain the urban commons - green commons, land commons, and water commons - in Ghana. The study, based on the determination of different theoretical scenarios for the urban commons, identified that decentralized urban planning can help sustain the urban commons, but it is operationalized in an unfavorable political environment. For green commons, there are competing interests and poor coordination amongst planning institutions, and the absence of self-organizing bodies in managing the use of such resources. For land commons, increased land litigations are characterized by corruption and poor management of land cases in the formal land courts, and despite the existence of self-organizing institutions, these institutions have failed to act responsibly to protect land commons due to the increasing demands and values (profitability) of lands in urban areas. For water commons, urban planning has not been fully decentralized and there is also the absence of self-organizing bodies in urban water use and management. This is coupled with the waning of customary water protection provisions in urban centers. Based on the findings, the study generally proposes institutional strengthening as the bedrock for enhancing the sustainability of the urban commons through urban planning and should therefore be of policy focus moving forward.

Optimization on structure and operation parameters of biofilter for decentralized sewage treatment

Aiming for treating decentralized domestic wastewater in rural China, this study evaluates the effects of ceramsite size and structure, and water recirculation parameters, upon the performance of recirculating biofilter (RBF). RBF shows stable capability of chemical oxygen demand (COD) remediation and ammonia nitrification. In addition, the microbial flora and structures of the various layers in the system are analyzed via high-throughput sequencing in order to study the microbial diversity. The results indicate that while the ceramic particle size has no significant influence on the COD remediation capacity, the ceramics with smaller particle sizes exhibit better ammonia nitrogen (NH₄⁺-N) removal ability, with a first-order linear relationship between the influent ammonia nitrogen load and the effluent NH₄⁺-N concentration in RBF (R² > 0.64). An increased hydraulic load and intermittent operation are shown to deteriorate the water quality with respect to NH₄⁺-N, while an increased recirculation ratio increases the removal rate of NH₄⁺-N from the effluent. Further, the water distribution time has a stronger effect upon the NH₄⁺-N concentration in the effluent than does the recirculation ratio. Moreover, the microbial structure of the multi-layer recirculating trickle biofilter varies significantly during the process. The results indicate that a high recirculation ratio, long water distribution time, and multi-layer structure will be beneficial for improving the pollutant treatment capacity of RBF.

Electrochemical iron production to enhance anaerobic membrane treatment of wastewater

Although iron salts such as iron(III) chloride (FeCl₃) have widespread application in wastewater treatment, safety concerns limit their use, due to the corrosive nature of concentrated solutions. This study demonstrates that local, electrochemical generation of iron is a viable alternative to the use of iron salts. Three laboratory systems with anaerobic membrane processes were set up to treat real wastewater; two systems used the production of either in-situ or ex-situ electrochemical iron (as Fe²⁺ and Fe²⁺(Fe³⁺)₂O₄, respectively), while the other system served as a control. These systems were operated for over one year to assess the impact of electrochemically produced iron on system performance. The results showed that dosing of electrochemical iron significantly reduced sulfide concentration in effluent and hydrogen sulfide content in biogas, and mitigated organics-based membrane fouling, all of which are critical issues inherently related to sustainability of anaerobic wastewater treatment. The electrochemical iron strategy can generate multiple benefits for wastewater management including increased removal efficiencies for total and volatile suspended solids, chemical oxygen demand and phosphorus. The rate of methane production also increased with electrochemically produced iron. Economic analysis revealed the viability of electrochemical iron with total cost reduced by one quarter to a third compared with using FeCl₃. These benefits indicate that electrochemical iron dosing can greatly enhance the overall operation and performance of anaerobic membrane processes, and this particularly facilitates wastewater management in a decentralized scenario.

Knowledge Atlas on the Relationship between Water Management and Constructed Wetlands—A Bibliometric Analysis Based on CiteSpace

Water management is a crucial resource conservation challenge that mankind faces, and encouraging the creation of manmade wetlands with the goal of achieving long-term water management is the key to long-term urban development. To summarise and analyse the status of the research on the relationship between water management and constructed wetlands, this paper makes use of the advantages of the bibliometric visualization of CiteSpace to generate country/region maps and author-collaboration maps, and to analyse research hotspots and research dynamics by using keywords and literature co-citations based on 1248 pieces of related literature in the core collection in the Web of Science (WoS) database. The existing research shows that the research content and methods in the field of constructed-wetland and water-management research are constantly being enriched and deepened, including the research methods frequently used in constructed wetlands in water management and in the research content under concern, the functions and roles of constructed wetlands, the relevant measurement indicators of the purification impact of constructed wetlands on water bodies, and the types of water bodies treated by constructed wetlands in water management. We summarise the impact pathways of constructed wetlands on water management, as well as the impact factors of constructed wetlands under water-management objectives, by analysing the future concerns in the research field to provide references for research.

Development of Rainfall-Runoff Models for Sustainable Stormwater Management in Urbanized Catchments

Modelling of stormwater networks and the related object (combined sewer overflows, diversion chambers, retention tanks) is a complex task requiring colleting of data with appropriate time and spatial resolution as well as application of adequate models. Often there is a need to find balance between the costs of conducting measurement (period, resolution) and the uncertainty of the model results. This paper presents an overview of simulation tools for sewerage networks modelling, related objects, as well as low-impact development (LID) systems in relation to the hydrodynamic and statistical models. Consecutive stages of data collection, sources of data uncertainty, limitations resulting from the adopted measurement methodology, as well as their influence on the simulation results and possible decision-making using the developed hydrodynamic or statistical model, are discussed. Attention is drawn to the optimization methods enabling reduction in the uncertainty of statistical models. The methods enabling the analysis of model uncertainty, as well as evaluation of its influence on the calculation results pertaining to stormwater hydrographs, retention tank capacity and combined sewers overflows, are also discussed. This is a very important aspect in terms of optimizing construction works in the sewerage network and designing their appropriate dimensions to achieve the assumed hydraulic effects.

Systematically assess the advancing and limiting factors of using the multi-soil-layering system for treating rural sewage in China: From the economic, social, and environmental perspectives

Solving the problem of rural sewage is considered an essential task in China's rural revitalization strategy. Based on the yearbook data of sewage treatment in rural areas between 2014 and 2019, although the rate of sewage treatment in rural areas of China showed an upward trend, it was still below 35%, mainly due to the lack of suitable sewage treatment technologies. Here, we discuss the multi-soil-layering (MSL) system, which is an emerging technology suitable for rural sewage treatment. It was deemed to overcome the shortcomings of current biological and ecological treatment technologies, such as complex operation, large area, and high operating costs. We used system dynamics to evaluate the advancing and limiting factors of MSL application for rural sewage treatment from the social, environmental, and economic dimensions. The results illustrated a complete causal loop diagram in which essential variables and relationships were concentrated in the technology, operation and maintenance, and satisfaction of farmers. The efficiency of MSL is the key variable affecting the final decision of the MSL application. Overall, using MSL to treat rural sewage could be an option to improve the rural environment in China. However, the scientific technological model for MSL should be further explored. This review provides guidance on how to promote MSL systems in rural areas.

In silico assessment of household level closed water cycles: Towards extreme decentralization

Water management in most of the developed world is currently practiced in a highly centralized manner, leading to major infrastructure and energy costs to transport water. To decrease the impacts of water scarcity and climate change, the decentralization of water can increase local robustness. In extremis, decentralization can involve building or house level water supply and treatment. Here, we constructed a MATLAB/Simulink model for two decentralized water management configurations at the household level, assuming the socio-environmental setting of Flanders, Belgium. Independence from the potable water grid and sewer system was pursued through rainwater harvesting, reuse of wastewater streams fit-for-purpose, and discharge via infiltration. The mass balance for water was calculated over the system boundaries showing high potential for independence from the grid with a reasonable treatment train and storage options. Next, the risk of contaminant accumulation within the circular system was assessed, showing a key limitation on decentralized system performance necessitating a system purge. Up to 59% of system rainwater usage was due to the replacement of this purge. Employing treatment units with high (95%) contaminant rejection efficiencies eliminated contaminant accumulation issues. The raw model output was quantitatively assessed by constructing four newly proposed key performance indicators (KPIs), quantifying system independence, circularity, drought tolerance and local water body recharge, which allowed for facilitated system comparison and communication to stakeholders. A sensitivity analysis was performed in which the effect of input parameter variability and uncertainty on system performance was quantified. The sensitivity analysis showed the importance of water recovery and contaminant removal efficiencies of the applied treatment technologies on system performance when contaminant accumulation in the system forms an issue. In systems not severely affected by pollutant accumulation, parameters such as inhabitant number and roof surface had the largest effect. As a whole, this work shows the potential of extreme decentralization of water systems and addresses the obstacle towards implementation formed by the accumulation of contaminants due to system circularity. Additionally, this study provides a framework for operational and technological decision support of decentralized household-scale water systems and, by extension, for future water policy-making.

Adaptive Resilience of Complex Safety-Critical Sociotechnical Systems: Toward a Unified Conceptual Framework and Its Formalization

Resilience is commonly understood as the capacity for a system to maintain a desirable state while undergoing adversity or to return to a desirable state as quickly as possible after being impacted. In this paper, we focus on resilience for complex sociotechnical systems (STS), specifically those where safety is an important aspect. Two main desiderata for safety-critical STS to be resilient are adaptive capacity and adaptation. Formal studies integrating human cognition and social aspects are needed to quantify the capacity to adapt and the effects of adaptation. We propose a conceptual framework to elaborate on the concept of resilience of safety-critical STS, based on adaptive capacity and adaptation and how this can be formalized. A set of mechanisms is identified that is necessary for STS to have the capacity to adapt. Mechanisms belonging to adaptive capacity include situation awareness, sensemaking, monitoring, decision-making, coordination, and learning. It is posited that the two mechanisms required to perform adaptation are anticipation and responding. This framework attempts to coherently integrate the key components of the multifaceted concept of STS adaptive resilience. This can then be used to pursue the formal representation of adaptive resilience, its modeling, and its operationalization in real-world safety-critical STS.

The role of climate change and decentralization in urban water services: A dynamic energy-water nexus analysis

Urban water services, including drinking water supply and wastewater treatment, are highly energy dependent, contributing to the challenges described under the water-energy nexus. Both future climate change and decentralized water system adoptions can potentially influence the energy use of the urban water services. However, the trend and the extent of such influences have not been well understood. In this study, a modeling framework was developed to quantify both the separate and the combined influences of climate change and decentralization on the life cycle energy use of the urban water cycle, using the City of Boston, MA as a testbed. Two types of household decentralized systems were considered, the greywater recycling (GWR) systems and the rainwater harvesting (RWH) systems. This modeling framework integrates empirical models based on multilinear regression analysis, hydrologic modeling, water balance models, and life cycle assessment to capture the complex interactions among centralized water services, decentralized water system adoptions, and climate parameters for cumulative energy demand (CED) assessment, considering all residential buildings in Boston. It was found that climate change alone will slightly increase the energy use of the centralized systems towards the end of the century, due to the cancelation effect amongst changes in water quality, flow rate, and space and water heating demand. When decentralization is considered alone, we found economically viable decentralized systems may not necessarily produce energy savings. In fact, RWH adoptions may increase energy use. When climate change and decentralization are combined, they will increase the water yield and cost savings of the decentralized systems, while reducing the energy use from the centralized systems. When the centralized systems are further added into the picture, the CED of the entire urban water cycle is projected to increase by 0.9% or 2.3% towards the end of the century under climate change if GWR or RWH systems are adopted by respective cost saving positive buildings.

Resilience Assessment and Critical Point Identification for Urban Water Supply Systems under Uncertain Scenarios

The urban water supply system environment is becoming more complicated and unpredictable than ever before in the context of global climate change and expanding urbanization. Existing studies have adopted either static or dynamic approaches to assess the resilience of water supply systems without combining the two. Previous literature mostly establishes rigid quantitative metrics for resilience assessment, often without depicting the dynamics and adaptability of system resilience. For example, these studies usually fail to provide a critical point for identifying system resilience. To accurately describe the dynamics and adaptability of water supply system resilience under uncertain scenarios, in this study, we constructed a comprehensive framework based on the qualitative assessment of the input parameters, combining static and dynamic assessment, with the latter playing a dominant role based on the system perspective of pressure–state–influence–response. Taking Qingdao as a case study, we combined this framework with the system resilience theory, and statically assessed the five types of capitals and three attributes of resilience with the capital portfolio approach (CPA). Then, we dynamically assessed the resilience of urban water supply systems and identified critical points with the dynamic socio-technical model coupled with system resilience and the fitting analysis method. The results are as follows: (1) the static assessment results demonstrate an imbalanced development in the levels of the five types of capitals (financial capital, management efficiency, infrastructure, available water resources, and adaptation) and three attributes (robustness, recoverability, and adaptability) in the water supply systems of Qingdao. (2) The dynamic assessment results show that the current resilience trajectory of the water supply systems in Qingdao is that of a city in transition. (3) The fitting analysis shows that robustness (RB) has a linear relationship with resilience, recoverability (RE) has a non-linear relationship with resilience, and the critical points are RB = 0.70 and RE = 1.20. The research findings provide a reference for studying resilience mechanisms, internal attribute relationships, and resilience enhancement measures of urban water supply systems.

Transitional Pathways towards Achieving a Circular Economy in the Water, Energy, and Food Sectors

Achieving sustainable socio-economic development requires approaches that enhance resource use efficiencies and can address current cross-sectoral challenges in an integrated manner. Existing evidence suggests an urgent need for polycentric and transformative approaches, as global and local systems have come under strain. This study conducted a systematic literature review at the global level to assess the progress made towards achieving a circular economy between 2010 and 2020, a period covering the formulation of the Sustainable Development Goals (SDGs) and the initial five years of their implementation. The focus was on the potential of improved water and energy use efficiency, linking them to food production within the context of a circular economy. Identifying successes, opportunities, challenges, and pathways towards a circular economy from the literature review facilitated developing a conceptual framework to guide strategic policy formulations towards a more sustainable economy. A combination of transformative approaches is analysed in an integrated way in response to the 2030 global agenda on sustainable development. Thus, the study is informed by the initiatives to attain SDGs and mitigating negative environmental impacts due to waste and pollution. The premise is to enhance transformational change as a catalyst for employment creation and the attainment of a green economy while reducing waste. Transformative approaches have been identified to provide pathways towards global climate targets and protection of the environment from further degradation. They are a catalyst to achieve SDG 12 on ensuring sustainable consumption and production patterns.

Comparative life cycle assessment of aerobic treatment units and constructed wetlands as onsite wastewater treatment systems in Australia

Life Cycle Assessment was used to evaluate onsite wastewater treatment systems (OWTS): aerobic treatment unit (ATU) with reinforced concrete (C.ATU) and HDPE (H.ATU) tank; and constructed wetland (CW) with three biochar concentrations in the substrate (0%; 10, and 20% v:v), dubbed CW.BC0, CW.BC10 and CW.BC20, respectively. CML 2001 in SimaPro^® was used to evaluate the impacts of the treatment of 1 m³ wastewater. The OWTS were compared on their overall environmental performance scores (OEP). ATUs have higher impacts on human toxicity, eutrophication, freshwater and marine ecotoxicity. The CW.BC20 has the lowest global warming impact (GWP) while CW.BC0 has the highest. Electricity consumption was the largest contributor to the impacts of the ATUs. PVC pipes, coir peat, geomembrane, and electronic devices were the biggest contributors to the impacts of the CWs. The OEP of the CWs were almost a third of the ATUs' (6.07E-03). Changes in electricity sources were tested according to the 2030-Australian targets; increasing renewables share improves the OEP of ATUs by 39%; nevertheless, CWs continue to outperform the ATUs. Variations in biochar biodegradation had a small effect on the OEP of CWs; being relevant only to GWP. This study provides a reference to policy makers for better evaluation of OWTS.

Optimal Implementation of Wastewater Reuse in Existing Sewerage Systems to Improve Resilience and Sustainability in Water Supply Systems

A transition from conventional centralized to hybrid decentralized systems has been increasingly advised recently due to their capability to enhance the resilience and sustainability of urban water supply systems. Reusing treated wastewater for non-potable purposes is a promising opportunity toward the aforementioned resolutions. In this study, we present two optimization models for integrating reusing systems into existing sewerage systems to bridge the supply–demand gap in an existing water supply system. In Model-1, the supply–demand gap is bridged by introducing on-site graywater treatment and reuse, and in Model-2, the gap is bridged by decentralized wastewater treatment and reuse. The applicability of the proposed models is evaluated using two test cases: one a proof-of-concept hypothetical network and the other a near realistic network based on the sewerage network in Chennai, India. The results show that the proposed models outperform the existing approaches by achieving more than a 20% reduction in the cost of procuring water and more than a 36% reduction in the demand for freshwater through the implementation of local on-site graywater reuse for both test cases. These numbers are about 12% and 34% respectively for the implementation of decentralized wastewater treatment and reuse.

Assessing the Impact of Water Efficiency Policies on Qatar’s Electricity and Water Sectors

Water and electricity have a unique relationship in the modern world as one requires the other in a complex system of networks to supply the utility to the customers. This energy–water interaction is especially peculiar in the Gulf Cooperation Council, where there are limited water resources, but extremely high use rates. Qatar provides a unique case in terms of extreme water scarcity and excessive water use. To understand the intricate network, this paper establishes an updated and comprehensive qualitative model of the water system in the country with the help of a water balance and system dynamics (causal loop diagram) methodology. Regression estimates are then used to estimate future water and energy consumption in addition to carbon dioxide emissions until the year 2050. Finally, system dynamics (stock and flow diagram) is used to determine the supply impacts of efficiency policies including limiting of groundwater abstraction to only 50 million m3, reduction of water consumption in the household, commercial and industrial sector by 10%, and gradual increase in the share of reverse osmosis (RO)-produced desalinated water to 50% in order to assess the supply volume, electricity consumption and CO2 emissions. The efficient use of water in different sectors of the economy results in a combined saving of 1222 GWh (8.1%) or 594,000 tons CO2. Furthermore, by moving to membrane-based desalination technology energy consumption and carbon dioxide emissions can be reduced by 3672 GWh (24.3%) and 1.8 million tons CO2, respectively. Further results suggest that while replacing groundwater with desalinated water can increase the energy consumption significantly, reuse of treated wastewater has almost the same footprint as groundwater, but can increase the resilience of the system considerably as groundwater abstraction levels are lowered to their renewal rates.

Key criteria for considering decentralization in municipal wastewater management

Wastewater pollution problems are associated with population growth and the concentration of population in large urban centers. According to United Nations projections for 2050, the world population will reach 9 billion people, increasing the pressures on water resources due to their demand and pollution. Based on UNICEF and World Health Organization estimates, 2.4 billion people worldwide currently lack access to improved sanitation facilities, with 946 million practicing open defecation. Decentralized wastewater treatment systems are a viable and necessary alternative for wastewater management, thus, minimizing environmental impacts, facilitating resource recovery, and providing rural and peri-urban inhabitants with access to basic sanitation. This literature review article uses the multicriteria analysis tool to present the key economic, institutional, social, environmental, and technological aspects, criteria, and indicators that must be considered for successful decentralized system implementation planning to strengthen basic sanitation service coverage in the rural and peri-urban areas where it does not exist.

Place-Based Citizen Science for Assessing Risk Perception and Coping Capacity of Households Affected by Multiple Hazards

Since hazards act upon vulnerability and exposure to become disasters, the understanding of societal challenges is key for disaster risk reduction. This condition is even more critical when more than one hazard is in place. Taking the case of flooding and water shortage, this study is built upon the premise that disasters are a social phenomenon; therefore, it is essential to comprehend the social context in which they occur. Particularly, this study aims to evaluate the similarities and differences in risk perception and the coping capacity of residents in the multiple-hazard context. For this, a place-based citizen science approach was developed in this study in Campina Grande, a semiarid region of Brazil, with the collaboration of 199 participants. Risk perception and coping capacity were analysed through the citizens’ participation, while combining subjective and objective methods. The results indicate that even though residents have experienced severe flooding and water shortages in the past, they still have low coping capacity. The findings highlight the need to combine a triad of societal challenges, namely information, trust, and incentives, to improve coping capacity in the future and increase resilience. This study underlines the need to understand multiple hazards according to social, spatial, and temporal scales in a socio-spatial perspective.

A Smart Water Grid for Micro-Trading Rainwater: Hydraulic Feasibility Analysis

Water availability is increasingly stressed in cities across the world due to population growth, which increases demands, and climate change, which can decrease supply. Novel water markets and water supply paradigms are emerging to address water shortages in the urban environment. This research develops a new peer-to-peer non-potable water market that allows households to capture, use, sell, and buy rainwater within a network of water users. A peer-to-peer non-potable water market, as envisioned in this research, would be enabled by existing and emerging technologies. A dual reticulation system, which circulates non-potable water, serves as the backbone for the water trading network by receiving water from residential rainwater tanks and distributing water to households for irrigation purposes. Prosumer households produce rainwater by using cisterns to collect and store rainwater and household pumps to inject rainwater into the network at sufficiently high pressures. The smart water grid would be enabled through an array of information and communication technologies that provide capabilities for automated and real-time metering of water flow, control of infrastructure, and trading between households. The goal of this manuscript is to explore and test the hydraulic feasibility of a micro-trading system through an agent-based modeling approach. Prosumer households are represented as agents that store rainwater and pump rainwater into the network; consumer households are represented as agents that withdraw water from the network for irrigation demands. An all-pipe hydraulic model is constructed and loosely coupled with the agent-based model to simulate network hydraulics. A set of scenarios are analyzed to explore how micro-trading performs based on the level of irrigation demands that could realistically be met through decentralized trading; pressure and energy requirements at prosumer households; pressure and water quality in the pipe network.

Study on the Domestic Water Utilization in Kota Metro, Lampung Province, Indonesia: Exploring Opportunities to Apply the Circular Economic Concepts in the Domestic Water Sector

Providing reliable public water service is a big challenge in Indonesia, especially for small cities, due to various constraints such as budget, regulation, and technical problems. Besides, people’s preferences play a significant role in domestic water utilization. This research particularly aims to identify factors influencing public preferences for domestic water use in Kota Metro, Lampung Province, Indonesia to find the reason why public water service is less preferable in this city. We did a household survey and performed a multinomial logistic regression and multiple correspondence analysis to investigate the preferable domestic water source and influential factors determining the choice. We found that accessibility and water quality are the two strongest motives in choosing domestic water use. Our analysis also shows that the respondent’s choice is influenced by his or her income, family size, and proximity to the pipe network. Subsequently, we synthesized our empirical findings and the existing situation of the domestic water fulfillment in Kota Metro to suggest an improvement proposal inspired by the circular economy concepts. We recommend a mixture of a pipe water service and community-based water management to improve the current domestic water fulfillment.

Biomimetic Organisations: A Management Model that Learns from Nature

Since the end of the last century, different approaches for corporate management have been appearing that try to incorporate the social advances that are being produced and disseminated thanks to the greater capacity of communication available through social networks and other traditional avenues. Among the best known are Corporate Social Responsibility, Sustainability, the Circular Economy, and Collaborative Economics. All of them add value to organisations, and all of them have a common characteristic: they are anthropocentric approaches. Our proposal goes a step further: we need a worldview that is capable of placing organisations in a position of continuous learning looking at nature, because it is the best way to integrate into it as a more ecosystem and thus achieve its flowering respecting the once to all the other subsystems that make up the planet: Organizational Biomimicry. This work compares the anthropocentric vision with the worldview at the same time that it offers a guide of the essential steps so that Organizational Biomimicry is the new model of corporate management.

A Resilient and Sustainable Water Sector: Barriers to the Operationalisation of Resilience

Global threats such as climate change, increasing urbanisation, and rapid population growth will continue to pose major challenges for the water sector over the coming decades. Questions over supply, delivery and demand, all form a central part of this argument with the themes of sustainability and resilience often included in the response. Recent events, along with reactive changes to national legislation and policy, have resulted in a need for the notion of resilience to develop from a theoretical concept to a tangible operational method. This commentary discusses barriers to the operationalisation of resilience in the water sector of England and Wales. The current privatised governance structure of the water sector is first discussed before the three main barriers to operationalisation—lack of agreed definition, metrics and the measuring of resilience—and the need to further acknowledge the ‘socio’ in socio-technical systems, are further explored. A deeper understanding of the notion of resilience in the context of the water sector, and how it can be successfully and effectively applied and implemented at an operational level, are crucial if the sector is to manage and respond to the aforementioned global challenges.

Enhancing Sustainability and Resilience through Multi-Level Infrastructure Planning

Resilient planning demands not only resilient actions, but also resilient implementation, which promotes adaptive capacity for the attainment of the planned objectives. This requires, in the case of multi-level infrastructure systems, the simultaneous pursuit of bottom-up infrastructure planning for the promotion of adaptive capacity, and of top-down approaches for the achievement of global objectives and the reduction of structural vulnerabilities and imbalances. Though several authors have pointed out the need to balance bottom-up flexibility with top-down hierarchical control for better plan implementation, very few methods have yet been developed with this aim, least of all with a multi-objective perspective. This work addressed this lack by including, for the first time, the mitigation of urban vulnerability, the improvement of road network condition, and the minimization of the economic cost as objectives in a resilient planning process in which both actions and their implementation are planned for a controlled, sustainable development. Building on Urban planning support system (UPSS), a previously developed planning tool, the improved planning support system affords a planning alternative over the Spanish road network, with the best multi-objective balance between optimization, risk, and opportunity. The planning process then formalizes local adaptive capacity as the capacity to vary the selected planning alternative within certain limits, and global risk control as the duties that should be achieved in exchange. Finally, by means of multi-objective optimization, the method reveals the multi-objective trade-offs between local opportunity, global risk, and rights and duties at local scale, thus providing deeper understanding for better informed decision-making.

Life cycle assessment of decentralized greywater treatment systems with reuse at different scales in cold regions

Decentralized source-separated wastewater treatment systems offer an attractive alternative to conventional centralized wastewater treatment systems in various regions, yet few system analyses specifically address decentralized greywater treatment over different scales. Here we present a comparative life cycle assessment (LCA) and focus on global warming potential (GWP), eutrophication potential (EUP) and human health - carcinogenic potential (HHCP) of decentralized greywater management systems at different scales for a hypothetical community in a cold (winter) region. To provide a comparison between nature-based and engineered greywater treatment solutions, constructed wetlands (CW) and membrane bioreactors (MBR), respectively, were investigated at three different scales; community (3500 person equivalent [PE]), neighborhood (350 PE) and household (a single household [up to 5 PE]). Conventional centralized wastewater treatment was also included as a business-as-usual (BAU) scenario. In the MBR scenarios, greywater reuse was also considered for multiple non-potable applications due to its high-quality effluent and subsurface garden irrigation was considered for reuse in the CW scenarios. For scenarios with the same treatment technology, larger scales reduced GWP, EUP and HHCP up to 57 kg CO₂-eq.PE^-1.y^-1, 0.2 kg N-eq.PE^-1.y^-1 and 5.3E-6 CTUh.PE^-1.y^-1, respectively, despite the need for more extensive wastewater networks. The CW scenarios at community and neighborhood scales outperformed the MBR and BAU scenarios for greywater treatment, while the community-scale MBR scenario may be environmentally preferable when large amount of greywater can be reused. The scale of decentralized systems, quantity of water reused and mix of electricity technologies all played important roles in determining GWP, EUP and HHCP values.

Transformative Approaches for Sustainable Water Management in the Urban Century

Sustainable Urban Water Management (SUWM) approaches highlighted in this special issue have the potential to contribute to the transformation of urban water systems. The aim of the transformation is to accommodate population and economic growth and at the same time enable a system which is environmentally sustainable and resilient to future challenges such as climate change. These approaches have increasingly entered mainstream dialogue over the last ten years as knowledge on the approaches has developed, and there is an acceptance that there needs to be a change to how urban water systems are designed and operated. However, there are still a range of aspects of these approaches that are maturing and require further research to realize the objectives of SUWM. The issue explored supply-side interventions, such as rainwater harvesting and stormwater harvesting, demand-side interventions, and water storage solutions that have the potential to enable a range of recycling technologies. The issue also highlighted a novel method for better managing the integrity of a conventional sewer system. Furthermore, there are articles that explore methods for integrated assessments, integrated decision making and an exploration of what factors may promote community adoption of technology.