Nitrite-dependent microbial utilization for simultaneous removal of sulfide and methane in sewers.

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.

Factors impacting water quality and quantity in rapidly expanding urban areas based on the DPSIR model: experiences and challenges from Addis Ababa City, Ethiopia.

Due to the increasing pressures of global change, such as urbanization, climate change, population growth, and socioeconomic changes, cities around the world are facing significant water challenges, both in terms of supply and quality. This emphasizes the need for concerted effort to manage water supplies effectively for sustainable development. The driver, pressure, state, impact, and response (DPSIR) model was applied in this study to determine the underlying causes of Addis Ababa's water supply and quality issues. Field observations, key informant interviews, and previously published reports were used to identify these variables, impacts, and coping mechanisms. The model suggests that issues with urban water are caused by inadequate waste management, fast urbanization, climate change, sociodemographic shifts, economic challenges, changes in land use and land cover, and institutional pressures. As a result, aquatic ecosystems endure damage and there is also an increase in water-related diseases and unmet water demand. Some of the responses to these effects include using bottled water, digging boreholes, harvesting rainwater, planting trees, and soliciting funds. The study concludes by recommending an integrated approach to managing the risks of declining water quality and shortage. This study will advance the important empirical understanding of how urban water supply and quality are impacted by environmental stresses on a global scale. It will also positively impact the development of sustainable water management policies and practices.

An integrated approach to decision-making variables on urban water systems using an urban water use (UWU) decision-support tool.

In response to pressing global challenges like climate change, rapid population growth, and an urgent need for sustainable infrastructure, cities face an immediate and crucial necessity to transition swiftly toward an integrated approach to managing urban water resources. This shift is not merely an option but an imperative, driven by the rapidly evolving urban landscape. In addressing this imperative, a crucial decision support tool that has emerged as an asset in the domain of urban water planning and management is the Urban Water Use (UWU) tool. This tool offers an integrated approach for strategic planning, promoting urban water conservation and environmental health through the investigation of interventions in urban infrastructure under different scenarios. In this study, the latest version of this UWU tool was deployed in a case study conducted in Almirante Tamandaré, Brazil. The objective was to evaluate how an integrated decision-making approach concerning urban water systems influences the efficiency and effectiveness of interventions, ultimately contributing to achieve widespread adoption, accessibility, and relevance of urban water services. The refined UWU tool evaluates a spectrum of measures across diverse scenarios, incorporating various drivers, focusing on the stakeholders' visions for the locality. These visions are composed of sustainability indicators, specifying different sets of target values and importance weights for each indicator. The approach followed in this study demonstrates how the effectiveness indexes can vary based on stakeholders' perception. Measures under Water Sensitive Urban Design and Water Demand Management strategies were deployed to simulate the response of urban water systems under three distinct scenarios, embracing the complexities of social dynamics and of climate change. The findings of the study emphasize that realizing a desired vision through selected measures relies significantly on the adoption of an integrated approach within the decision-making process. The stakeholders' perception of how indicators should be weighted while defining the vision was found to significantly impact the effectiveness range of these measures.

Development of a multicriteria model for crises in urban water supply and its application to the case of Brasilia, Brazil.

The expansion of urban water supply crisis (UWC) cases, a context characterized by an inadequate ratio between water consumption and supply capacity, has motivated researchers to search for tools to solve the problem. The objective of this study is to develop a multicriteria tool to help select the solution alternative for UWC cases. The tool (called UWC-MCDA) is based on obtaining consensus on various multicriteria methods for selecting alternatives to solve UWC cases. The proposed methodology consists of the following steps: (1) defining the criteria, (2) defining weights, (3) defining the alternative, (4) defining multicriterial decision support methods, (5) coding the UWC solution alternative selection model, (6) evaluation of the model coding, (7) application of the model coding, and (8) sensitivity analysis. The methods PROMETHEE II, TOPSIS, ELECTRE III, and Consensus ranking are used. The case study considered was the Administrative Region of Brasilia, in the Federal District of Brazil. A multicriteria tool to help select the solution alternative for UWC cases was developed in an easy-to-use environment (Visual Basic for Applications, MS Excel). The UWC-MCDA is able to identify and prioritize, among a set of possible alternatives, the most appropriate solution for the case in question. For the case study, the UWC-MCDA indicated the best alternatives for regulating water consumption, strengthening sanitation service operators and good water conservation practices. Integr Environ Assess Manag 2023;19:99-113. © 2022 SETAC.

Tacit knowledge in water management: a case study of Sponge City.

Sustainable, resilient urban water management is fundamental to good environmental and public health. As an interdisciplinary task, it faces enormous challenges from project complexity, network dynamics and the tacit nature of knowledge being communicated between actors involved in design, decisions and delivery. Among others, some critical and persistent challenges to the implementation of sustainable urban water management include the lack of knowledge and expertise, lack of effective communication and collaboration, and lack of shared understanding and context. Using the Chinese Sponge City programme as a case study, this paper draws on the perspectives of Polanyi and Collins to investigate the extent to which knowledge can be used and exchanged between actors. Using Collins' conceptualisation of the terrain of tacit knowledge, the study identifies the use of relational, somatic and collective tacit knowledge (CTK) in the Sponge City pilot project. Structured interviews with 38 people working on a Sponge City pilot project provided data that was rigorously analysed using qualitative thematic analysis. The paper is original in identifying different types of tacit knowledge in urban water management, and the potential pathways for information and messages being communicated between actors. The methods and results provide the groundwork for analysing the access and mobilisation of tacit knowledge in the Sponge City pilot project, with relevance for other complex, interdisciplinary environmental projects and programmes.

Photoelectrocatalysis on TiO2 meshes: different applications in the integrated urban water management.

Recently, among AOPs, photoelectrocatalysis (PEC) on TiO2 is gaining interest. In this study, five different real waters sampled in four different points of the integrated urban water management (IUWM) system were tested with PEC and UV alone, for comparison. This work aims to verify the effect of the PEC suggesting the optimal position in IUWM system where the PEC should be located to obtain the best performance. In groundwaters (GWs), PEC effectively removed atrazine-based compounds (> 99%), trichloroethylene, and perchloroethylene (96%), after 15 min of reaction time. However, given the low concentrations of emerging compounds, the synergistic effect of UV radiation with the catalyst and with the polarization of the mesh was not visible, with very few differences compared with the results obtained with UV alone. Pharmaceutical industrial wastewater (IWW) showed a significant increase in biodegradability after 2 h, both if subjected to PEC or UV (200%), despite the absence of COD removal. The PEC applied on IWW from a sewage sludge treatment plant allowed to effectively remove the COD (39.6%) and increase the biodegradability (300%). Good results in terms of COD removal (33.9%) and biodegradability increase (+900%) were also achieved testing PEC on wastewater treatment plant effluent. Except for GWs, PEC allowed significant EEO savings respect to UV alone (76.2-99.1%).

From 'government' to 'governance': A quantitative transition analysis of urban wastewater management principles in Stellenbosch Municipality.

Water demand continues to increase amid shrinking natural water sources in the Western Cape Province of South Africa. This holds true for Stellenbosch Municipality, which is situated in the Western Cape. The prevailing draught, coupled with rainfall projections predicting that the region will be in a high-risk draught category by 2040, prompted municipal authorities to devise alternative water sources, such as urban waste water recycling (UWWR), to augment its water supplies. This water management approach is a component of integrated urban water management (IUWM), which stems from the water 'governance' paradigm. Research on the transition process from a 'government' to a 'governance' UWWR paradigm is limited both in the global south and in South Africa. Hence, the main objective of this study was to investigate the action knowledge required for a sustainable transition from a 'government' to an IUWW 'governance' paradigm in the context of Stellenbosch town. The study adopted a transdisciplinary research methodology, while the transformative research paradigm guided the research. Quantitative data collection from a single case study, namely Stellenbosch town, was through the administration of a questionnaire distributed to purposefully sampled participants. ANOVA statistical tools analysed the data. The study ascertained that transitioning frameworks considered in this study could guide a transition process of migrating from conventional urban wastewater management government towards IUWM governance principles in Stellenbosch town and other global south locations.

Holistic Analysis of Urban Water Systems in the Greater Cincinnati Region: (2) Resource Use Profiles by Emergy Accounting Approach.

With increasing populations, mounting environmental pressures and aging infrastructure, urban water and wastewater utilities have to make investment decisions limited by both economic and environmental constraints. The challenges facing urban water systems can no longer be sustainably solved by traditional siloed water management approaches. A central premise of contemporary urban water management paradigms is that in order for urban water systems to be more sustainable and economical, an improvement in resource use efficiency at system level must be achieved. This study provides a quantification of the total resource use of a typical urban water system exemplified in Greater Cincinnati region from raw water extraction for drinking water to wastewater treatment and discharge, providing a better understanding of resource expenditure distributions within the system and a necessary benchmark to which future system improvements can be compared. The emergy methodology was used so that the total environmental work required to produce disparate system inputs could be expressed using a common unit. The results were compared to the concurring life cycle assessment (LCA) and life cycle costing (LCC) results of the same system. Emergy results highlight drinking water treatment and drinking water distribution as two resource-intensive stages, with energy for pumping and chemicals for conditioning representing the greatest inputs to the former and energy for pumping and metals for piping representing the greatest inputs to the latter. For wastewater collection and treatment stages, aeration and sludge handling were identified as the highest emergy unit processes, mostly due to energy use. Comparison with LCA results substantiate the environmental concerns associated with energy use in the drinking water treatment and distribution stages but indicate that environmental burdens associated with infrastructure are more dependent upon upstream resource use rather than downstream environmental impact. Results from emergy, LCA and LCC point towards aeration and sludge handling as two unit processes on the wastewater side that are particularly costly and environmentally impactful. Results in total are used to suggest alternative strategies that can alleviate identified environmental burdens and economic costs.

Integrated water resources management for emergency situations: A case study of Macau.

Integrated urban water management (IUWM) is a useful tool that can be used to alleviate water resource shortages in developing regions like Macau, where 98% of the raw water comes from mainland China. In Macau, scarce water resources deteriorate rapidly in emergency situations, such as accidental chemical spills upstream of the supply reservoir or salty tides. During these times, only the water from the two freshwater reservoirs in Macau can be used. In this study, we developed urban water management optimization models that integrated the raw water supply from the two reservoirs with various proposed governmental policies (wastewater reuse, rainwater collection, and water saving). We then determined how various water resource strategies would influence the urban water supply in Macau in emergency situations. Our results showed that, without imported raw water, the water supply from only the two Macau reservoirs would last for 7.95days. However, when all the government policies were included in the model, the supply could be extended to 13.79days. Out of the three non-conventional water resources, wastewater reuse is the most beneficial for increasing the Macau water supply, and rainwater collection also has great potential.