Improving eco-efficiency of wastewater treatment plants (WWTPs) has been identified as being essential for
achieving urban sustainability. Several previous papers have evaluated the eco-efficiency of WWTPs using data
envelopment analysis (DEA) models. However, those models provided only a static assessment in that they
ignored possible fluctuations over time within each plant. To overcome this temporal limitation, this paper
evaluates dynamic eco-efficiency (changes in eco-productivity over time) of WWTPs using the dynamic weighted
Russell directional distance model (WRDDM). This approach allows one to obtain an eco-productivity change
index for each major component of the WRDDM model (costs, pollutants removal, and greenhouse gas emissions).
Our results illustrate that although eco-productivity improved in half of the WWTPs we assessed, there
was still potential for improving some eco-efficiency components. Moreover, operational costs and greenhouse
gases emissions were the main drivers reducing eco-productivity. This paper demonstrates the importance of
evaluating change in eco-productivity over time and in identifying the drivers associated with those changes,
both of which can be used to support decision-making focused on the sustainability of WWTPs
