Energy Monitoring And Benchmarking In Wastewater Treatment Plants Using The ENERWATER Approach

Abstract

One of the higher costs of wastewater services is the energy consumption. The total electricity consumption in wastewater treatment plants (WWTPs) corresponds to about 1% of the total electricity consumption per year of a country (Cao et al., 2011). In order to compare WWTPs having different processes and scheme configurations, the most useful methodology is energy efficiency measurement using benchmarking procedures (Parena et al., 2002). However, the available audit methodologies do not support well the decisions of the water utilities in order to best target their actions to improve the energy efficiency. Traditionally, energy consumption of a WWTP has been simplistically reported using global KPIs such as kWh/m3 (Mizuta and Shimada, 2010) or kWh/PE (Krampe, 2013; Balmer, 2000). As WWTPs are composed by several stages, each one with a different function, the use of specific KPIs for each treatment stage or function is more appropriate (Longo et al., 2016). A standard methodology is required in order to carry out the energy audit in WWTPs (Tao et al., 2009). Horizon2020 ENERWATER project (www.enerwater.eu ) deals, inter alia, with development of a standard methodology for continuously assessing, labelling and improving the overall performance of WWTPs. The objective of this study is to illustrate the application of the ENERWATER methodology to three real wastewater treatment plants (WWTPs). The ENERWATER methodology considers two approaches for the determination of energy consumption in WWTPs, namely Rapid Audit and Decision Support. The Rapid Audit allows for a quick estimation of the water treatment energy index (WTEI) based on existing information such as historical data pertaining to energy use records along with influent and effluent quality values. The Decision Support requires intensive monitoring across a WWTP of energy usage and water quality parameters that provides an accurate and detailed calculation of WTEI for each stage as well as its overall value for the plant. For the sake of brevity only the results of the Rapid Audit methodology will be presented here.