Abstract
As a method for eco-efficiency analysis, environmental cost efficiency (ECE) indicators have been proposed for the end-of-pipe (EOP) systems that referred to the techniques achieving environmental benefit under economic cost. The wastewater treatment plant (WWTP) belongs to the EOP systems; however, few studies used the ECE indicators for the sustainability evaluation. Here, this study first proposed the following processes that had been excluded in the current ECE framework and thus limited the potential application in WWTP: (1) the direct impact of wastewater on receiving water, (2) the migration and transformation of water pollutants affected by the self-purification mechanisms of receiving water. To address the aforementioned processes, this study extended the framework of ECE indicators by means of incorporating the potential growth of microorganisms as the characterization state and integrating the water quality models with the characterization models. To investigate the applicability, a full-scale WWTP was selected as the study case and the eco-efficiency of the increasing levels of sewage treatment was evaluated. The case outcome showed that, with the extended ECE indicators, the analysis of eco-efficiency could be directly related to the specific locations and could determine the specific distance ranges within which the scenarios changing were considered efficient. Moreover, the eco-efficiency could be investigated under more concrete and flexible situations because the extended framework of ECE indicators was able to include more information, such as different types of receiving water or different environmental conditions of certain water body.
Highlights
Eco-efficiency analysis enables the assessment of sustainability from combined perspectives of environment and economy and has been increasingly applied to evaluate the performance of waste management systems [1,2,3,4,5,6,7]
This paper extended the framework of ECE indicators for the eco-efficiency analysis in wastewater treatment plants
In the environmental dimension of ECE indicators, the potential growth of microorganisms was defined as the characterization state, and the water quality models were incorporated to capture the migration and transformation of water pollutants
Summary
Eco-efficiency analysis enables the assessment of sustainability from combined perspectives of environment and economy and has been increasingly applied to evaluate the performance of waste management systems [1,2,3,4,5,6,7]. Environmental cost efficiency (ECE) is established for the end-of-pipe (EOP) systems, which refer to the techniques achieving environmental benefit under a certain amount of economic cost [6]. The pollutant-removal techniques, designed and operated to dispose wastewater or solid waste, exactly belong to the EOP system. The ECE method has been efficiently implemented regarding the optimized management of municipal solid waste [2]. Upon the evaluation of wastewater treatment plants (WWTPs), the ECE method has been rarely used. In order to promote the future application in this regard, Water 2020, 12, 454; doi:10.3390/w12020454 www.mdpi.com/journal/water
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