Measuring Energy Demand and Efficiency at WWTPs: An Econometric Approach

Abstract

As the number of wastewater treatment plants (WWTPs) increases worldwide and the effluent quality requirements become more demanding, the issue of energy efficiency has been attracting increasing attention from an environmental and economic point of view. However, defining and measuring energy efficiency in WWTPs is still a challenge. Energy efficiency is typically approximated by energy intensity, i.e. kWh/m³. However WWTPs can perform different functions (i.e. removing of COD, removing of N and/or P, resource recovery, producing an effluent free of pathogens), or perform the same function with different technologies, making the comparison of WWTPs a challenging task. Thus, common energy intensity indicators have limited value, as they do not provide enough information of the WWTPs operation. Furthermore, changes in energy intensity are just approximate indicators for changes in energy efficiency since they are affected by external (exogenous) factors.

This study describes how linear regression analysis can be used as a means to estimate energy efficiency in WWTPs, by accounting for the impact of external factors and the diversity of treatment functions. Likewise, based on the analysis of a relatively large sample of WWTPs, the effect of some important variables on energy efficiency is discussed, which open possibilities for improving benchmarking comparability of WWTPs.