Abstract
The assessment of wastewater treatment plant (WWTP) performance has gained the interest of water utilities and water regulators. Eco-efficiency has been identified as a powerful indicator, as it integrates economic and environmental variables into a single index. Most previous studies have employed traditional data envelopment analysis (DEA) for the evaluation of WWTP eco-efficiency. However, DEA allows the selection of input and output weights for individual WWTPs for the calculation of eco-efficiency scores. To overcome this limitation, we employed the double-frontier and common set of weights methods to evaluate the eco-efficiency of a sample of 30 WWTPs in Spain. The WWTPs were ranked based on eco-efficiency scores derived under several scenarios including best- and worst-case scenarios; this approach to performance assessment is reliable and robust. Twenty-six of the 30 WWTPs were not classified as eco-efficient, even under the most favorable scenario, indicating that these facilities have substantial room for the reduction of costs and greenhouse gas emissions. The ranking of WWTPs varied according to the scenario used for evaluation, which has notable consequences when eco-efficiency scores are used for regulatory purposes. The findings of this study are relevant for water regulators and water utilities, as they demonstrate the importance of weight allocation for eco-efficiency score estimation.
Highlights
Wastewater treatment is essential for the protection of human health and environmental sustainability [1]
WWTPs are complex, resource-intensive facilities, and the improvement of their sustainability is a relevant goal for water regulators and water utilities
Among several methodological approaches employed for assessment, data envelopment analysis (DEA) is among the most frequently used, as it provides an index integrating environmental and economic variables, thereby enabling the holistic assessment of WWTP performance
Summary
Wastewater treatment is essential for the protection of human health and environmental sustainability [1]. The performance and efficiency of WWTPs are related closely to the pollutant removal efficiency, resource consumption, and environmental impacts such as greenhouse gas (GHG) emissions [14]. Schaltegger and Sturm [19] first defined eco-efficiency as the ratio between the value added and the environmental impact. This concept entails the production of more goods and services with fewer resources and a minimal environmental impact [20]; the prefix “eco” represents ecological and economic dimensions [21]. For WWTPs, eco-efficiency entails the removal of more pollutants from wastewater while incurring fewer economic costs and emitting fewer GHGs [16,17,18]
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