Characterizing water pollution potential in life cycle impact assessment based on bacterial growth and water quality models

For the life cycle assessment (LCA) of wastewater management, eutrophication is considered the most relevant factor. However, eutrophication is not the only pathway through which wastewater influences the environment, and merely characterizing eutrophication potential is not sufficient for the LCA framework to reflect the influence of wastewater. This study defines the Bacterial Depletion of Oxygen (BDO)-a new impact category that represents the oxygen depleting potential caused by the growth of microorganisms-and characterization models and characterization factors are developed for the application of BDO.Water quality models (both oneand two-dimensional) are incorporated into the BDO characterization models so that the LCA framework includes some spatially differentiated factors, and can be used to estimate the direct impact of wastewater on receiving environment (I_BDO value). Based on three case studies, this study demonstrates how the BDO category can be applied for the evaluation of wastewater management. Results show that increases in the downstream distance and self-purification coefficients reduce the I_BDO value, whereas the increase in water velocity raises the I_BDO value. Future integration of the BDO category with water quality models must link the dilution effect of water bodies, the environmental carrying capacity of receiving water, and the distribution of water pollutants in eutrophication and bacterial oxygen depletion.