This document defines a methodology for determining and assessing the energy efficiency of Waste Water Treatment Plants (WWTP). The methodology aims at describing, in a systematic way, the various steps required to establish the Water Treatment Energy Index (WTEI) of a particular WWTP. The methodology includes the classification of WWTPs in different types, identification of different stages of treatment, identification of key performance indicators (KPIs), overview of existing energy monitoring standards and the detailed description of the methodology, including a step by step guideline of how to apply and implement it. The methodology is divided in 2 sub-methods that should be selected and followed according to the following goals:
- The Rapid Audit (RA) method 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 aim of this methodology is to provide a WWTP energy benchmark, a rapid tool to identify energy efficiencies and inefficiencies so further actions can be planned, as well as to evaluate the impact of WWTP retrofitting. The Rapid Audit methodology is detailed step by step in Clause 4 of this TR and can be used as a standalone document. The application of the Rapid Audit methodology to one real WWTP is shown in Annex A.
- The Decision Support (DS) method 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. The goal of this assessment is to serve as a diagnosis of the functions/equipment in a plant that may lead to poor energy efficiency performance. The Decision Support methodology is detailed step by step in Clause 5 of this TR and can be used as a standalone document. The application of the Decision Support methodology to one real WWTP is shown in Annex B.