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As urban economies continue to evolve, the water distribution networks (WDNs) are expanding in scale and becoming more interconnected, leading to increased carbon emissions from operations and maintenance. Consequently, enhancing the stability and safety of WDNs while saving energy has emerged as a primary research focus. This study abandoned the original use of high economic costs for post-maintenance of WDNs. Instead, it reshaped the traditional water distribution topology to form a dynamic, storable, energy-efficient "WDN self-help" model. Drawing inspiration from the "deep tunnel" project in drainage systems, the proposal was to leverage underground spaces to create a deep aqueduct (DA) complementing the traditional WDN, forming a three-dimensional (3D) WDN. Hydraulic and water quality analyses of varying scales of the 3D WDN model demonstrated its superior ability to equalize node pressures, reduce pipeline head losses, and maintain water quality for end-users. Reliability assessments of the 3D WDN revealed enhanced system robustness for medium-to large-scale distributions, while energy consumption analyses indicated a significant increase in water supply energy utilization and significant long-term reductions in carbon footprint. A practical case study was presented to validate the effectiveness of the 3D WDN concept, confirming its ability to reliably distribute water even in the event of a failure. Finally, an estimate of the retrofit cost and the static payback period of the 3D WDN was conducted. This study aims to provide a theoretical reference for the renovation of water supply projects or the optimal design of new WDNs in the context of carbon neutrality.

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Urban water systems in China are facing multiple challenges, including rapid urbanisation, climate change and infrastructure ageing. It is crucial to evaluate their environmental performance from a holistic perspective in planning and management processes. To the best of our knowledge, there is a lack of nationwide life cycle assessment (LCA) studies on China's urban water systems that cover all system stages. Therefore, this study aims to present a comprehensive and nationwide LCA analysis that pinpoints the environmental hotspots and their major sources across China. This study was conducted based on water utility databases at the province level, covering water abstraction and treatment, waterwork sludge treatment, water distribution, sewage collection, stormwater drainage, wastewater treatment and sewage sludge treatment. Nine environmental impact categories were calculated and analysed. The results reveal the inequity of environmental impacts across provinces, with overall impacts geographically higher in the east and south, lower in the west and north. However, at the functional unit level, the impacts in the northern and northeastern provinces are higher than other regions. Most environmental categories are dominated by multiple water system stages. The analyses of underlying drivers found that purchased electricity is the primary source of several environmental impacts. This study provides a holistic understanding of the environmental performance of China's urban water systems, offers some insights for comprehensive decision-making support on sustainable water system management, and can also serve as a benchmark for future scenario analysis to explore options for reducing environmental impact.

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Mathematical modeling plays a crucial role in understanding and managing urban water systems (UWS), with mechanistic models often serving as the foundation for their design and operations. Despite the wide adoptions, mechanistic models are challenged by the complexity of dynamic processes and high computational demands. Data-driven models bring opportunities to capture system complexities and reduce computational cost, by leveraging the abundant data made available by recent advance in sensor technologies. However, the interpretability and data availability hinder their wider adoption. This paper advocates for a paradigm shift in the application of data-driven models within the context of UWS. Integrating existing mechanistic knowledge into data-driven modeling offers a unique solution that reduces data requirements and enhances model interpretability. The knowledge-informed approach balances model complexity with dataset size, enabling more efficient and interpretable modeling in UWS. Furthermore, the integration of mechanistic and data-driven models offers a more accurate representation of UWS dynamics, addressing lingering uncertainties and advancing modelling capabilities. This paper presents perspectives and conceptual framework on developing and implementing knowledge-informed data-driven modeling, highlighting their potential to improve UWS management in the digital era.

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In the last century, the issue of "water reserves" has become a remarkably strategic topic in modern science and technology. In this context, water resource treatment and management systems are being developed in both agricultural and urban area scenarios. This can be achieved using superabsorbent polymers (SAPs), highly cross-linked hydrogels with three-dimensional, hydrophilic polymer structures capable of absorbing, swelling and retaining huge amounts of aqueous solutions. SAPs are able to respond to several external stimuli, such as temperature, pH, electric field, and solution composition and concentration. They can be used in many areas, from sensor technology to drug delivery, agriculture, firefighting applications, food, and the biomedical industry. In addition, new categories of functional SAP-based materials, mainly superabsorbent polymer composites, can also encapsulate fertilizers to efficiently provide the controlled release of both water and active compounds. Moreover, SAPs have great potential in wastewater treatment for the removal of harmful elements. In this respect, in the following review, the most promising and recent advances in the use of SAPs and composite SAPs as tools for the sustainable management and remediation of water resource are reviewed and discussed by identifying opportunities and drawbacks and highlighting new challenges and aims to inspire the research community.

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The water diversion project is an effective engineering approach to overcome water scarcity as a water source for the area. However, the complex environmental conditions of long-distance water diversion bring many uncertainties for water security. In this study, we assessed the pollution condition and risk levels of emerging contaminants and traditional contaminants in the water and soil along a water diversion project in Tianjin. Then, we assessed the influence of eco-economic characteristics on environmental conditions and established a comprehensive assessment framework of water source sustainability by analytic hierarchy process (AHP). The results showed that excessive nutrient elements and heavy metal pollution mainly contributed to environmental problems in the water source area. Contrary to pollution assessment, the soil ecosystem was more subject to environmental pressure due to atmospheric deposition. The health risk assessment indicated that all contaminants had negligible non-carcinogenic risks for adults, with arsenic being considered a priority pollutant. The statistical analysis results indicated land use allocation was the most important factor in the environmental management of the water source area. According to the result of the integrated environmental assessment, the main characteristics of pressure zones were high pollution levels and human activity intensity. It is urgent to control agricultural pollution and allocate land use rationally for water source pressure zones. By considering the risks of traditional and emerging contaminants in water and soil, this study could support urban water source management and the sustainable development of the water diversion project.

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Urban wastewater treatment plants (WWTPs) and drinking water treatment plants (DWTPs) play vital roles in the urban water cycle, ensuring access to safe drinking water and maintaining aquatic ecosystems. This study comprehensively assessed the occurrence and risks of pharmaceuticals and personal care products (PPCPs) in urban WWTPs and DWTPs. Our findings revealed widespread PPCPs presence, with concentrations ranging from <1 ng/L to several thousand ng/L. Significant regional disparities in occurrence and composition were observed linked to population types and economic structures. Furthermore, strong correlations were observed between DWTPs and WWTPs indicating consistent transport and transformation patterns of PPCPs within the urban water cycle. Approximately two-thirds of PPCPs were degraded post-WWTP treatment, with about one-tenth persisting in drinking water following surface water dilution and purification processes. Thus, we suggested that controlling the total concentration of the five priority PPCPs in the effluent from the WWTP to <1100 ng/L have potential to reduce the environmental and health risk of PPCPs. Additionally, this research identified influential water quality parameters, such as pH, dissolved oxygen, and temperature, through redundancy analysis. This research underscores the importance of establishing emission standards to mitigate PPCP-related risks and supports sustainable urban water system advancement.

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Water resource management, as a foundation for supporting sustainable urban development, has garnered increasing attention from scholars. Developing effective water resource management plans is a major challenge faced by countries worldwide. This study uses the 2015 Water Pollution Control and Prevention Action Plan (WPCAP) in China as a natural experiment and employs a Difference-in-Differences (DID) model to estimate the relationship between WPCAP and urban water pollution from 2010 to 2021. The findings are as follows: 1) WPCAP reduces water pollution. 2) WPCAP decreases water pollution in high-policy-pressure cities but increases water pollution in low-policy-pressure cities within a 60 km radius, particularly having a significantly negative impact on water pollution in low-policy-pressure cities with low altitude. 3) optimizing industrial and domestic water use, as well as enhancing sewage treatment capabilities, are crucial pathways through which WPCAP reduces water pollution. Additionally, WPCAP significantly improves water pollution control capabilities in cities with abundant water resources, large cities, and industrialized cities. 4) although WPCAP's ability to control water pollution increases management costs, it also raises residential income and promotes population growth. These findings have important implications for the sustainable development of water resources in emerging countries, including China.

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Sustainable urban water management is crucial for meeting the growing demands of urban populations. This study presents a novel approach that combines time series clustering, seasonal analysis, and entropy analysis to uncover residential water consumption patterns and their drivers. Using a three-year dataset from the SmartH2o project, encompassing 374 households, we identify nine distinct water consumption patterns through time series clustering, leveraging Dynamic Time Warping (DTW) as the optimal similarity measure. Multiple linear regression reveals key household characteristics influencing water usage behaviors, such as the number of bathrooms and appliance efficiency ratings. Seasonal analysis uncovers temporal dynamics, highlighting shifts towards lower consumption during summer months and increased variability in transitional seasons. Entropy analysis quantifies the diversity and complexity of water consumption at both cluster and household levels, informing targeted interventions. This comprehensive, granular approach enables the development of personalized water conservation strategies and policies, empowering water utilities to optimize resource management and contribute to sustainable urban water practices.

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Chemicals are commonly dosed in sewer systems to reduce the emission of hydrogen sulfide (H2S) and methane (CH4), incurring high costs and environmental concerns. Nitrite dosing is a promising approach as nitrite can be produced from urine wastewater, which is a feasible integrated water management strategy. However, nitrite dosing usually requires strict conditions, e.g., relatively high nitrite concentration (e.g., ∼200 mg N/L) and acidic environment, to inhibit microorganisms. In contrast to "microbial inhibition", this study proposes "microbial utilization" concept, i.e., utilizing nitrite as a substrate for H2S and CH4 consumption in sewer. In a laboratory-scale sewer reactor, nitrite at a relatively low concentrations of 25-48 mg N/L was continuously dosed. Two nitrite-dependent microbial utilization processes, i.e., nitrite-dependent anaerobic methane oxidation (n-DAMO) and microbial sulfide oxidation, successfully occurred in conjunction with nitrite reduction. The occurrence of both processes achieved a 58 % reduction in dissolved methane and over 90 % sulfide removal in the sewer reactor, with microbial activities measured as 15.6 mg CH4/(L·h) and 29.4 mg S/(L·h), respectively. High copy numbers of n-DAMO bacteria and sulfide-oxidizing bacteria (SOB) were detected in both sewer biofilms and sediments. Mechanism analysis confirmed that the dosed nitrite at a relatively low level did not cause the inhibition of sulfidogenic process due to the downward migration of activity zones in sewer sediments. Therefore, the proposed "microbial utilization" concept offers a new alternative for simultaneous removal of sulfide and methane in sewers.

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Urban water systems are potential sources of secondary microplastics (MPs) as well as a distributor of MPs in the environment. In the present study, the presence of MPs in the urban water systems of the Tehran Metropolitan (Capital of Iran) was investigated. In addition, the probable relationship of MPs with different land uses (i.e., residential-commercial, forest, military, and highway) was assessed. The results showed that all parts of Tehran's urban water system in the study area were contaminated with MPs (107.1 ± 39, 37.8 ± 10.5, 48.3 ± 3.1, 46.9 ± 5.6, 59.4 ± 26.5, 1.7, 2.0 ± 0.6, 7.9 ± 1, 1.8 ± 0.2 particles/liter at the residential, integrated, military, forest, highway runoffs, drinking water, groundwater, seasonal river, and the effluent of the wastewater treatment plants; respectively). However, significant differences were found between different land uses. As expected, the residential runoff had the highest rate of MPs pollution, with 107.1 ± 39 particles/liter. According to the obtained results and our estimation, more than five million MPs/day can enter into the water bodies and soil of the study area through the wastewater treatment plants. While there are significant differences in MPs in the different land uses, our findings suggest that residential areas and highways need further attention in controlling the spread of MPs in urban areas.

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Turbidity stands as a crucial indicator for assessing water quality, and while turbidity sensors exist, their high cost prohibits their extensive use. In this paper, we introduce an innovative turbidity sensor, and it is the first low-cost turbidity sensor that is designed specifically for long-term stormwater in-field monitoring. Its low cost (USD 23.50) enables the implementation of high spatial resolution monitoring schemes. The sensor design is available under open hardware and open-source licences, and the 3D-printed sensor housing is free to modify based on different monitoring purposes and ambient conditions. The sensor was tested both in the laboratory and in the field. By testing the sensor in the lab with standard turbidity solutions, the proposed low-cost turbidity sensor demonstrated a strong linear correlation between a low-cost sensor and a commercial hand-held turbidimeter. In the field, the low-cost sensor measurements were statistically significantly correlated to a standard high-cost commercial turbidity sensor. Biofouling and drifting issues were also analysed after the sensors were deployed in the field for more than 6 months, showing that both biofouling and drift occur during monitoring. Nonetheless, in terms of maintenance requirements, the low-cost sensor exhibited similar needs compared to the GreenSpan sensor.

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Dissemination of antibiotic resistance genes (ARGs) in urban water bodies has become a significant environmental and health concern. Many approaches based on real-time quantitative PCR (qPCR) have been developed to offer rapid and highly specific detection of ARGs in water environments, but the complicated and time-consuming procedures have hindered their widespread use. Herein, we developed a facile one-step approach for rapid detection of ARGs by leveraging the trans-cleavage activity of Cas12a and recombinase polymerase amplification (RPA). This efficient method matches the sensitivity and specificity of qPCR and requires no complex equipment. The results show a strong correlation between the prevalence of four ARG markers (ARGs: sul1, qnrA-1, mcr-1, and class 1 integrons: intl1) in tap water, human urine, farm wastewater, hospital wastewater, municipal wastewater treatment plants (WWTPs), and proximate natural aquatic ecosystems, indicating the circulation of ARGs within the urban water cycle. Through monitoring the ARG markers in 18 WWTPs in 9 cities across China during both peak and declining stages of the COVID epidemic, we found an increased detection frequency of mcr-1 and qnrA-1 in wastewater during peak periods. The ARG detection method developed in this work may offer a useful tool for promoting a sustainable urban water cycle.

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Addressing urban water management challenges requires a holistic view. Sustainable approaches such as blue-green infrastructure (BGI) provide several benefits, but assessing their effectiveness demands a systemic approach. Challenges are magnified in informal areas, leading to the combination of integrated urban water management (IUWM) with BGI as a proposed solution by this research. We employed the Urban Water Use (UWU) model to assess the effectiveness index (EI) of BGI measures in view of IUWM after stakeholder consultation. The procedure in this novel assessment includes expert meetings for scenario building and resident interviews to capture the community's vision. To assess the impact of IUWM on the effectiveness of BGI measures, we proposed a simulation with BGI only and then three simulations with improvements to the water and sewage systems. The results of the EI analysis reveal a substantial improvement in the effectiveness of BGI measures through IUWM combination. Moreover, we offer insights into developing strategies for UWU model application in informal settlements, transferrable to diverse urban areas. The findings hold relevance for policymakers and urban planners, aiding informed decisions in urban water management.

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This study thoroughly explores the application of Ultraviolet (UV) water treatment technology in urban wastewater treatment and water supply in China, highlighting its crucial role in enhancing water quality safety. UV technology, with its environmentally friendly and low-carbon characteristics, is deemed more in line with the demands of sustainable development compared to traditional chemical disinfection methods. The widespread application of UV technology in urban wastewater treatment in China, particularly in the context of urban sewage treatment, is examined. However, to better promote and apply UV technology, there is a need to deepen the understanding of this technology and its application among a broad base of users and design units. The importance of gaining in-depth knowledge about the performance of UV water treatment equipment, the design calculation basis, and operational considerations, as well as the ongoing development of relevant standards, is underscored to ensure that the equipment used in projects complies with engineering design and production requirements. Furthermore, the positive trend of UV technology in the field of advanced oxidation, indicating a promising trajectory for engineering applications, is pointed out. Regarding the prospects of industrial development, a thorough analysis is conducted in the article, emphasizing the necessity for all stakeholders to collaborate and adopt a multi-level approach to promote the sustainable development and application of UV water treatment technology. This collaborative effort is crucial for providing effective safeguards for China's environment, ecology, and human health.

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Sewage treatment involves a trade-off of land vs. energy and the location of installing Sewage Treatment Plants (STPs) strongly impacts the decisions regarding treatment technologies. In the wake of rapid urbanization, deteriorating freshwater quality and water scarcity, it is crucial to plan adequate and low-cost sewerage infrastructure that can improve the quality of life in rural and urban areas. The present work involves a novel life cycle analysis through six scenarios generated from a holistic perspective that can aid urban planners and urban local bodies in planning the sewage treatment facilities in their cities, towns or villages. Instead of planning sewerage infrastructure for a long-term period of thirty years, it is suggested to create and operate the STPs only for the upcoming decade. Further, owing to the drawbacks of mechanized and natural treatment systems, adopting a mix of these treatment approaches in planning infrastructure is suggested and the benefits of implementing the same are quantified and discussed. Implementing these strategies results in almost 30 % cost savings and 40 % reduction in greenhouse gas emissions, hence, investing in land for natural treatment systems is suggested instead of incurring heavy electricity bills for mechanized treatment systems. The land cost significantly affects the decision-making regarding treatment technology selection; hence, the variation in the life cycle cost of different sewage treatment approaches is assessed for varying land rates in India.

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As urbanization accelerates, understanding and managing carbon emissions from urban sewer networks have become crucial for sustainable urban water cycles. This review examines the factors influencing greenhouse gas (GHG) emissions within urban sewage systems, analyzing the complex effects between water quality, hydrodynamics, and sewer infrastructure on GHG production and emission processes. It reveals significant spatiotemporal heterogeneity in GHG emissions, particularly under long-term scenarios where flow rates and temperatures exhibit strong impacts and correlations. Given the presence of fugitive and dissolved potential GHGs, standardized monitoring and accounting methods are deemed essential. Advanced modeling techniques emerge as crucial tools for large-scale carbon emission prediction and management. The review identifies that traditional definitions and computational frameworks for carbon emission boundaries fail to fully consider the inherent heterogeneity of sewers and the dynamic changes and impacts of multi-source pollution within the sewer system during the urban water cycle. This includes irregular fugitive emissions, the influence of stormwater systems, climate change, geographical features, sewer design, and the impacts of food waste and antibiotics. Key strategies for emission management are discussed, focusing on the need for careful consideration of approaches that might inadvertently increase global emissions, such as ventilation, chemical treatments, and water management practices. The review advocates for an overarching strategy that encompasses a holistic view of carbon emissions, stressing the importance of refined emission boundary definitions, novel accounting practices, and comprehensive management schemes in line with the water treatment sector's move towards carbon neutrality. It champions the adoption of interdisciplinary, technologically advanced solutions to mitigate pollution and reduce carbon emissions, emphasizing the importance of integrating cross-scale issues and other environmentally friendly measures in future research directions.

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The failure of sewage network systems can lead to the introduction of external water, impacting the capacity, performance, and environmental sustainability of urban infrastructures. This study examined methods for identifying and quantifying external water in a sewage system in cold climate conditions through the analysis of stable isotope of oxygen (δ18O) and hydrogen (δ2H) from samples, and continuous temperature monitoring, followed by the simulation of the network's hydraulics and temperature profile. The assessment was conducted during periods of low and high groundwater levels, specifically during dry weather flow. In comparison, the yearly trends of infiltration and inflow rates were assessed utilizing the moving minimum method. Using δ18O as a tracer, daily infiltration rates of 5.8 % and 35 % were estimated for periods of low and high groundwater levels, respectively. Using the outputs of the thermodynamic model, temperature was used as a tracer and the daily infiltration rates were found to be 1.5 % and 21.9 % for the same periods. The infiltration and inflow rate for the year in question was estimated to be 23 % using the moving minimum method. The findings of this study demonstrate the temporal variability of infiltration in networks and highlight the need for, as well as the potential of, a multi-faceted approach and continuous monitoring for the accurate estimation of external water before sewage network renovations are carried out.

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The absence of a sewer system and inadequate wastewater treatment plants results in a discharge of untreated wastewater to the urban drainage channels and pollutes receiving waters. Field visits were carried out to observe water quality parameters such as dissolved oxygen (DO), biochemical oxygen demand (BOD), and chemical oxygen demand (COD) in an urban drainage system (Kolshet drain) in Thane City, Mumbai Metropolitan Region, India. Dye-tracing studies using rhodamine WT dye were used for computing the velocity, discharge, and dispersion coefficient of the drain. The data analysis shows that the BOD and COD values in the drain are higher than the permissible limits (30 mg L-1 for BOD and 250 mg L-1 for COD), which is not suitable for disposal to any receiving water body. Also, the DO was less than the permissible limit of a minimum of 3 mg L-1 (for the survival of aquatic life). It is seen that the higher BOD load significantly reduced the DO throughout the drain. The Water Quality Analysis Simulation Program (WASP 8.32, 2019) developed by the US Environmental Protection Agency (USEPA) has been used for the simulation of the DO and BOD in the drainage channel. The model simulates an appropriate estimate of the expected variation of DO and BOD at points of interest. The modeling for the Kolshet drain is expected to enable better estimates of the wastewater parameters and the pollution transport in the drain for planning purposes.

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The proton-pump inhibitor pantoprazole (PPZ) is one of the most consumed pharmaceuticals worldwide. Despite its high usage, reported PPZ concentrations in environmental water samples are comparatively low, which can be explained by the extensive metabolism of PPZ in the human body. Since most previous studies did not consider human PPZ metabolites it can be assumed that the current environmental exposure associated with the application of PPZ is substantially underestimated. In our study, 4'-O-demethyl-PPZ sulfide (M1) was identified as the predominant PPZ metabolite by analyzing urine of a PPZ consumer as well as the influent and effluent of a wastewater treatment plant (WWTP) using liquid chromatography coupled to high resolution mass spectrometry (LC-HRMS). M1 was found to be ubiquitously present in WWTP effluents (max. concentration: 3 000 ng/L) and surface waters in Germany. On average, the surface water concentrations of M1 were approximately 30 times higher than those of the parent compound PPZ. Laboratory scale experiments demonstrated that activated carbon can considerably adsorb M1 und thus improve its removal during wastewater and drinking water treatment. Laboratory ozonation experiments showed a fast oxidation of M1, accompanied by the formation of several ozonation products. Certain ozonation products (identities confirmed via synthesized reference standards) were also detected in water samples collected after ozonation in a full-scale WWTP. Overall lower signal intensities were observed in the effluents of a sand filter and biologically active granular activated carbon filter, suggesting that the compounds were significantly removed during these post-ozonation treatment stages.

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Urban surface water pollution poses significant threats to aquatic ecosystems and human health. Conventional nitrogen removal technologies used in urban surface water exhibit drawbacks such as high consumption of carbon sources, high sludge production, and focus on dissolved oxygen (DO) concentration while neglecting the impact of DO gradients. Here, we show an ecological filter walls (EFW) that removes pollutants from urban surface water. We utilized a polymer-based three-dimensional matrix to enhance water permeability, and emergent plants were integrated into the EFW to facilitate biofilm formation. We observed that varying aeration intensities within the EFW's aerobic zone resulted in distinct DO gradients, with an optimal DO control at 3.19 ± 0.2 mg L-1 achieving superior nitrogen removal efficiencies. Specifically, the removal efficiencies of total organic carbon, total nitrogen, ammonia, and nitrate were 79.4%, 81.3%, 99.6%, and 79.1%, respectively. Microbial community analysis under a 3 mg L-1 DO condition revealed a shift in microbial composition and abundance, with genera such as Dechloromonas, Acinetobacter, unclassified_f__Comamonadaceae, SM1A02 and Pseudomonas playing pivotal roles in carbon and nitrogen elimination. Notably, the EFW facilitated shortcut nitrification-denitrification processes, predominantly contributing to nitrogen removal. Considering low manufacturing cost, flexible application, small artificial trace, and good pollutant removal ability, EFW has promising potential as an innovative approach to urban surface water treatment.