Special Issue "Efficient Water and Energy Management in Urban Water Systems"

A special issue of Water (ISSN 2073-4441). This special issue belongs to the section "Water-Energy Nexus".

Deadline for manuscript submissions: closed (30 April 2022) | Viewed by 2704

Special Issue Editors

Dr. Dália Cruz Loureiro
E-Mail Website
Guest Editor
Hydraulics and Environment Department, Laboratório Nacional de Engenharia Civil, Lisbon, Portugal
Interests: energy; efficiency; performance assessment; urban water systems; water
Dr. Catarina Silva
E-Mail Website
Guest Editor
Hydraulics and Environment Department, Laboratório Nacional de Engenharia Civil, Lisbon, Portugal
Interests: urban water systems; wastewater treatment; energy; performance assessment

Special Issue Information

Dear Colleagues,

Urban water systems (UWSs) are energy-intensive worldwide, mainly for drinking-water pumping and aeration in wastewater treatment. In recent years, systemic approaches to assess multiple sources of inefficiency in drinking water systems (e.g., pump equipment, inadequate layout and operation and water losses) have started to be explored, with a high potential for improving efficiency. There remains a need to adapt and explore these approaches to wastewater and stormwater systems to assess inefficiencies associated with sewer inflow, infiltration and network layout. Similarly, recent developments have shown a high potential to promote energy efficiency through better operation and adequacy of treatment capacity in wastewater treatment plants. Moreover, energy recovery from turbines or wastewater has yet to be fully exploited. Approaches that allow a comprehensive assessment of UWS energy efficiency between the main stages of UWSs—drinking water abstraction and transport, drinking water treatment, drinking water transport and distribution, wastewater collection and transport, wastewater treatment and discharge and water reclamation and reuse—can significantly contribute to the decarbonization of the urban water sector.

For this Special Issue on “Efficient Water and Energy Management in Urban Water Systems”, we are interested in comprehensive approaches for assessing energy efficiency in UWSs and their demonstration in real case studies for the diagnosis, selection, implementation, and monitoring of improvement measures.

Dr. Dália Cruz Loureiro
Dr. Catarina Silva
Guest Editors

Manuscript Submission Information

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Keywords

  • energy
  • efficiency
  • urban water systems
  • performance assessment systems
  • effectiveness
  • diagnosis

Published Papers (4 papers)

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Research

Article
A Comprehensive Derivation and Application of Reference Values for Benchmarking the Energy Performance of Activated Sludge Wastewater Treatment
Water 2022, 14(10), 1620; https://doi.org/10.3390/w14101620 - 18 May 2022
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Abstract
Wastewater treatment plants (WWTPs) are facing challenges concerning the service’s effectiveness and reliability, as well as the efficiency and sustainability of resource utilization, where energy represents one of the higher costs in activated sludge (AS) treatment. This paper presents the latest developments in [...] Read more.
Wastewater treatment plants (WWTPs) are facing challenges concerning the service’s effectiveness and reliability, as well as the efficiency and sustainability of resource utilization, where energy represents one of the higher costs in activated sludge (AS) treatment. This paper presents the latest developments in the new energy performance indices (PXs) we have been developing for benchmarking, i.e., assessing and improving the performance of this widely used treatment. PXs compare the energy consumption with the energy requirements for the carbon and nitrogen removals needed for the plant’s compliance with the discharge consents (the closer they are, the better the performance). PXs are computed by applying to the state variables a performance function that is defined by the reference values for excellent, acceptable, and unsatisfactory performance. This paper shows the rationale for selecting the state variables for the AS energy performance and the comprehensive derivation of the equations to determine the reference values for energy consumption, which incorporate the effect of key parameters (flows, concentrations, and operating conditions). Reference values for the operating conditions affecting the energy performance are also proposed. A sensitivity analysis identified the key parameters for improving the aeration performance: α, F, and SOTE for air diffusers, and α and N0 for mechanical aerators. Fourteen Portuguese urban WWTPs (very diverse in size and inflows) were analyzed, and aeration (0.08–1.03 kWh/m3) represented 25–80% of total energy consumption (0.23–1.30 kWh/m3). The reference values for excellent performance were 0.23–0.39 kWh/m3 (P25–P75) for AS systems with air diffusers and 0.33–0.80 kWh/m3 for those with mechanical aerators. A comprehensive application in one WWTP (16–18 d solids retention time) showed the system’s ability at identifying which operating conditions to adjust (to F/M ratio lower than 0.09 d−1 and decreasing aeration during the low season) to improve the energy performance/savings while maintaining the treatment’s effectiveness and reliability. Full article
(This article belongs to the Special Issue Efficient Water and Energy Management in Urban Water Systems)
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Article
Water, Energy, and Emissions Nexus: Effect of Inflows in Urban Drainage Systems
Water 2022, 14(6), 868; https://doi.org/10.3390/w14060868 - 10 Mar 2022
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Abstract
The urban water sector significantly contributes to energy consumption and greenhouse gas (GHG) emissions. Detailed assessment of the wastewater system input provides opportunities for improving the water, energy, and emissions nexus. The inflow of water not requiring treatment into wastewater systems is acknowledged [...] Read more.
The urban water sector significantly contributes to energy consumption and greenhouse gas (GHG) emissions. Detailed assessment of the wastewater system input provides opportunities for improving the water, energy, and emissions nexus. The inflow of water not requiring treatment into wastewater systems is acknowledged worldwide. These undue inflows can increase the footprint of these systems. Together with flooding and discharges, monitoring of undue inflows is not a common practice in water utilities. Three levels of analysis are proposed to assess the magnitude of the impact of undue inflows in the water–energy–greenhouse gas (W-E-G) emissions nexus: at a national level, calculation of performance indicators using yearly data; at the utility level, performance indicators calculations using yearly, monthly, and sub-daily data; at the subsystem level, calculations using mathematical modeling. Results show the implications of undue inflows on energy and GHG emissions, including the effect of flooding and discharges. The importance of undue inflows in the W-E-G nexus is sustained by the results of three case studies in Portugal. Each level of analysis is tailored to the information available, allowing a step-by-step understanding of the relationship between water, energy consumption, and emissions of the urban drainage inflows. Full article
(This article belongs to the Special Issue Efficient Water and Energy Management in Urban Water Systems)
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Article
Experimental Outdoor Public Lighting Installation Powered by a Hydraulic Turbine Installed in the Municipal Water Supply Network
Water 2022, 14(5), 710; https://doi.org/10.3390/w14050710 - 23 Feb 2022
Viewed by 504
Abstract
Sustainability and energy prices make the use of energy obtained from renewable sources on an urban scale and for isolated local facilities necessary for municipal authorities. Moreover, when the demand of energy is at night, as for street lighting installations, the use of [...] Read more.
Sustainability and energy prices make the use of energy obtained from renewable sources on an urban scale and for isolated local facilities necessary for municipal authorities. Moreover, when the demand of energy is at night, as for street lighting installations, the use of accumulative systems is necessary, which means a major drawback due to a short lifetime expectancy and high cost. The use of batteries can require more than 70% of the budget of these lighting systems and has a critical impact in the project. The problem to solve is finding different renewable energy sources that can produce energy throughout the day, especially during the night, at the same time at which it is consumed. As one of the competences of municipal authorities is water supply networks, this paper analyzes the use of energy recovery turbines within these installations as an alternative to photovoltaic generators. To study the viability and effectiveness of this alternative, the water flows available in the network of a medium-size municipality were monitored and analyzed in depth to assess the amount of recoverable energy. In addition, an energy recovery turbine (ERT) station was set up, installing a bypass around one of the pressure-reducing valves (PRV) of the installation where energy is dissipated without practical use. The results obtained imply that the system proposed has economical and technical viability, is reliable and guarantees full service in all the seasons’ conditions. Moreover, the needs of the energy storage capacity are much lower (~8%) than with solar panels. Full article
(This article belongs to the Special Issue Efficient Water and Energy Management in Urban Water Systems)
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Article
Managing Apparent Loss and Real Loss from the Nexus Perspective Using System Dynamics
Water 2022, 14(2), 231; https://doi.org/10.3390/w14020231 - 13 Jan 2022
Cited by 1 | Viewed by 442
Abstract
When water utilities establish water loss control programs, they traditionally focus on apparent loss rather than real loss when considering economic feasibility in the water sector. There is an urgent need for new management approaches that can address complex relationships and ensure the [...] Read more.
When water utilities establish water loss control programs, they traditionally focus on apparent loss rather than real loss when considering economic feasibility in the water sector. There is an urgent need for new management approaches that can address complex relationships and ensure the sustainability of natural resources among different sectors. This study suggests a novel approach for water utilities to manage water losses from the water-energy (WE) Nexus perspective. The Nexus model uses system dynamics to simulate twelve scenarios with the differing status of water loss and energy intensities. This analysis identifies real loss as one of the main causes of resource waste and an essential factor from the Nexus perspective. It also demonstrates that the energy intensity of each process in the urban water system has a significant impact on resource use and transfer. The consumption and movement of resources can be quantified in each process involved in the urban water system to distinguish central and vulnerable processes. This study suggests that the Nexus approach can strongly contribute to quantifying the use and movement of resources between water and energy sectors and the strategic formulation of sustainable and systematic water loss management strategies from the Nexus perspective. Full article
(This article belongs to the Special Issue Efficient Water and Energy Management in Urban Water Systems)
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