The Development of a Framework for Assessing the Energy Efficiency in Urban Water Systems and Its Demonstration in the Portuguese Water Sector

Abstract

Urban water systems (UWSs) are energy-intensive worldwide, particularly for drinking-water pumping and aeration in wastewater treatment. Usual approaches to improve energy efficiency focus only on equipment and disregard the UWS as a continuum of stages from source-to-tap-to-source (abstraction/transport—treatment—drinking water transport/distribution—wastewater and stormwater collection/transport—treatment—discharge/reuse). We propose a framework for a comprehensive assessment of UWS energy efficiency and a four-level approach to enforce it: overall UWS (level 1), stage (level 2), infrastructure component (level 3) and processes/equipment (level 4). The framework is structured by efficiency and effectiveness criteria (an efficient but ineffective infrastructure is useless), earlier and newly developed performance indicators and reference values. The framework and the approach are the basis for a sound diagnosis and intervention prioritising, and are being tested in a peer-to-peer innovation project involving 13 water utilities (representing 17% of the energy consumption by the Portuguese water sector in 2017). Results of levels 1–3 of analysis herein illustrated for a water utility demonstrate the framework and approach potential to assess UWS effectiveness and energy efficiency, and to select the stages and infrastructures for improvement and deeper diagnosis.

Assessing Future Water Demand and Associated Energy Input with Plausible Scenarios for Water Service Providers (WSPs) in Sub-Saharan Africa

“…The benefits of pursuing joint water and energy efficiency for water services providers are outlined in [6,8] for Portugal, Romania [48] and Italy [49]. Such efforts lead to saving not only water and the associated energy input but also reductions in the energy costs and energy demand associated with water losses.…”

“…The maintenance schedules were mostly scheduled on monthly basis. The first question posed in the selection of the WSPs as suggested in [6], was: is energy efficiency an issue for the WSPs and if so, is it likely to be an issue of major concern as water demand grows? This was an important reflection since some WSPs are largely gravity-fed, with relatively low energy costs compared to their total operational costs.…”

“…In addition, most WSPs concentrate on efforts to reduce daily volume of water losses alone. However, such efforts are not sufficient to support impactful operational efficiency and sustainability of services since water loss reduction interventions including pressure management, leaks detection and repair also affect energy demand [6][7][8].…”

A comprehensive performance assessment system for diagnosis and decision-support to improve water and energy efficiency and its demonstration in Portuguese collective irrigation systems

“…PIs are expressed by the ratio between two variables of the same nature. In essence, the numerator expresses the objective of the indicator (e.g., real losses, network failures), and the denominator represents a related system scale (e.g., network length) (Loureiro et al, 2020). The PIs are calculated for a reference period, generally one year, and the value found does not issue judges, requiring comparison with a reference.…”

Performance Assessment System for Energy Efficiency in Wastewater Systems

“…For the wastewater subsector, existing studies are limited and tend to concentrate on individual assets, such as wastewater treatment facilities [16,17] or pumping stations [18,19], with very few existing developments centred on the integrated analysis of energy efficiency in the wastewater system as a whole. A recent study [20] analysed the energy use and efficiency in this subsector integrated in a broad urban water-cycle analysis. For the few specific studies found, none uses a tailored performance assessment system (PAS) to support energy management.…”