Data of Portuguese wastewater treatment plants (WWTPs) were analyzed in order to compare their energy and environmental performances. Several absolute and ratio indicators were considered, namely, electricity consumption, CO2 emissions from electricity, biochemical oxygen demand removal and the corresponding ratio indicators where each of the previous amounts was divided by total volume treated. Groups for statistical analysis were established considering different factors (population equivalent, size, etc.) and Kruskal-Wallis test was applied to assess the effect of these factors on the indicators considered. Significant differences were found for population equivalent and size for the three absolute indicators.
Moreno, R., Correia, M., & Martins, F. (2017). Energy and environmental performance of wastewater treatment plants: A statistical approach. In Energy Procedia (Vol. 136, pp. 296–301). Elsevier Ltd. https://doi.org/10.1016/j.egypro.2017.10.252