A novel energy balance tailored for wastewater systems

This paper presents a novel energy balance scheme tailored for assessing energy efficiency in wastewater systems. It provides a consistent method to calculate the energy components associated with wastewater transport processes, allowing the quantification of the main water-energy inefficiencies. Three assessment levels are described (macro, meso and micro-level), depending on available information and scope. This balance allows a holistic approach of wastewater systems energy efficiency, including the system layout, losses in pipes/manholes, energy associated with undue inflows, exceedance volumes and energy recovery. The energy balance is applied to realcase studies. The energy associated with undue inflows represents from 20% to 44% of the external energy, with low average efficiencies of wastewater pumping systems (34%) and inflow intrinsic energy representing 64% of the total energy. This energy balance supports the performance diagnosis and the development of energy efficiency improvement measures.