Evaluating the Energy Performance of 20 Portuguese Wastewater Treatment Plants

Abstract

Wastewater treatment plants (WWTPs) perform a prominent role in minimizing adverse environmental and human health impacts by subjecting wastewater to proper treatment, which ensures the quality of the treated water before discharging or reusing. Due to the complexity and diversity of processes involved, WWTPs are regarded as energy-intensive facilities, with energy costs accounting the second largest share of their operating costs. Energy demand in this sector is expected to continue the growth shown in the last decades due to the increase in the number of people gaining access to improved sanitation facilities and to more stringent regulatory and environmental protection standards. Consequently, to ensure the sector’s long-term sustainability it is essential to evaluate and improve the efficiency of the WWTPs using a holistic approach, by integrating environmental and economic features. In this paper, data from 20 Portuguese WWTPs located at the North of Portugal were analysed to compare their energy performance. For this, some simple performance indicators are employed and the underlying factors affecting energy consumption are evaluated. From this study is possible to verify that, for the sampled WWTPs, population equivalent and size do not influence their energy requirements, while the presence of a primary treatment stage shows some influence. Moreover, it also shows that, despite allowing some interesting conclusions, comparing WWTPs should not be performed using only a few simple KPIs and must include other features that influence their process to avoid biased conclusions.