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.
Highlights
Energy efficiency is inextricably linked to the economic and environmental sustainability of urban water systems (UWSs)
This paper presents a framework for comprehensively assessing energy efficiency in urban water systems
We propose a set of performance indicators (PIs) for each stage that focuses on aspects of the quality of service related to energy consumption or efficiency
Summary
Energy efficiency is inextricably linked to the economic and environmental sustainability of urban water systems (UWSs). In Portugal, the UWSs represent 3%–4% of the total national electricity consumption [3], but it is one of the sectors with the highest number of energy-intensive facilities at the national level [4]. A high-pressure level in drinking water systems increases water losses and pipe bursts and, besides the associated energy inefficiencies, the occurrence of failures due to pipe bursts can limit the service provided. Energy costs are mainly associated with pumping in drinking water networks and wastewater networks and with aeration in wastewater treatment. Some of these costs are inevitable for service provision, but some are due to inefficiencies of diverse nature, which can often be greatly reduced. Energy consumption from external sources in the
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