Energy Benchmarking as a Tool for Energy-Efficient Wastewater Treatment: Reviewing International Applications

This review presents an assessment of international wastewater treatment plant (WWTP) energy benchmarking studies and provides for the first time a detailed historical evolution of seminal European benchmarking methodology for the international water sector. We commence by comparing international applications of energy performance assessment and how the different methods have been applied and have evolved. More specifically, we investigate how international studies have measured WWTP energy performance and what are the different views in relation to energy performance reference value, whether the energy consumption should be related to the number of people connected, the applied load, treated wastewater volume, and the advantages and disadvantages of different approaches. International literature sources were identified using targeted keyword searches using Google Scholar in order to capture a broad range of scholarly and technical works. The review then follows with a detailed account of the origin and development of the seminal (German) energy benchmarking methodologies, delivered here for the first time and opening up previously inaccessible literature to an international audience. The review finds that despite its long-term use, disagreement remains regarding the most suitable energy benchmarking performance metrics and there is currently no internationally agreed approach to assess the energy performance of a WWTP. It further highlights that the European approach to energy benchmarking demonstrates that methodical optimisation of WWTPs and application of identified energy-saving measures, presents great opportunities to deliver achievable, environmentally and economically favourable change to water industry practice. Nevertheless, site-specific factors such as differing discharge conditions, topographical boundary conditions, wastewater volume and composition need to be considered when adapting and applying energy benchmarking methodologies elsewhere, and these factors should be taken into consideration by wastewater practitioners during energy benchmarking assessments.