Abstract
This paper presents and discusses the application of a novel energy balance scheme for assessing energy efficiency in wastewater systems. The energy balance is demonstrated with a Portuguese real-life case study, using mathematical modelling to estimate the different energy components and to compute two energy efficiency indices. The total inflow intrinsic energy can represent a significant amount (>95%) of the total energy used in systems mainly composed of gravity sewers. The total input energy is significantly (four-times) higher in the wet season than in the dry season, mostly due to undue inflows (e.g., direct rainfall and infiltration). The potential for energy recovery strongly depends on the available head and flow rate at the delivery point, being 0.01 kWh/m3 in the current case, with a project payback period of 4 years. The energy balance components and the respective energy efficiency indices strongly depend on the considered reference elevation. Thus, a unique regional reference elevation is recommended in the calculations.
Highlights
IntroductionEnergy efficiency in the water industry is often regarded as an operational issue focused mostly on pumping and treatment equipment or processes improvement, regarded as a management efficiency target to be achieved [1]
Infrastructures 2021, 6, 141. https://Energy efficiency in the water industry is often regarded as an operational issue focused mostly on pumping and treatment equipment or processes improvement, regarded as a management efficiency target to be achieved [1]
The current paper aims to apply and discuss the energy balance developed for wastewater systems at the micro-level, using mathematical simulations to describe the flow throughout the system
Summary
Energy efficiency in the water industry is often regarded as an operational issue focused mostly on pumping and treatment equipment or processes improvement, regarded as a management efficiency target to be achieved [1]. Climate change is challenging the water sector to optimize energy use and limit GHG emissions in the current daily operations. Aware of the need to reduce energy consumption and the associated costs, water utilities are currently looking for innovative ways to improve energy efficiency in their services by improving equipment efficiency, optimizing pump scheduling and changing the system layout [5], as well as recovering the excessive energy whenever feasible [6,7]. There remains a need to adapt and explore alternative approaches, mainly to wastewater and stormwater systems, to assess the inefficiencies associated with the sewer inflow and network layout
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