Life cycle assessment in wastewater treatment: influence of site-oriented normalization factors, life cycle impact assessment methods, and weighting methods

Abstract

This present study aims to analyze the differences in results of different site-directional life cycle assessment (LCA) methods applied in the field of wastewater treatment. Site-generic methods were employed and compared with China-specific methods on a full-scale wastewater treatment case. A set of Chinese normalized factors were developed and employed to compare with world normalization factors. No substantial discrepancies in results were obtained from the two different sets of normalization factors. In the phase of life cycle impact assessment, the e-Balance showed substantial discrepancies in results, compared with the CML method that is widely applied in LCA. The discrepancies were mainly attributed to the cause that in e-Balance more emphasis is on regional water pollution potential (that is: chemical oxygen demand (COD) as an independent impact category). Moreover, discrepancies in the results were also investigated by applying different site-directional weighting methods. Besides the specific locations where the weighting methods were designed for, this study showed that employing different environmental indicators in impact categories was another important factor that resulted in differences in the LCA results of the different weighting methods.