Development of Integrated Assessment Tool for Wastewater Treatment Plant Considering Classification by Carbon Origin

Abstract

To estimate greenhouse (GHG) gas emissions from wastewater treatment plants (WWTP), there is a need to model and evaluate the entire WWTP. Accordingly, a benchmarking tool that combines Activated Sludge Model (ASM), which describes biological treatment in a bioreactor, and Anaerobic Digestion Model (ADM), which describes anaerobic digestion in a digester, has been used. However, an elemental balance is required for consideration including sludge incineration and since carbon dioxide composed of biogenic carbon does not contribute to global warming, it is necessary to consider only fossil-derived carbon for a more reliable Life Cycle CO₂ (LCCO₂) assessment. Accordingly, firstly, an integrated assessment tool combining elemental balance including carbon, ASM, and ADM was developed. This makes it possible to carry out LCCO₂ assessments of GHG emissions from entire WWTPs. Second, the carbon origins of the entire WWTP were classified. Using previous studies, it is established a percentage of fossil-derived carbon per parametric component, which were defined and classified in ASM and ADM model and applied to the entire WWTP. The LCCO₂ assessment, which takes into account the origin of the carbon, shows that WWTP emits 8.71 % more GHGs compared to the result without considering the origin of the carbon. Through the integrated assessment tool presented in this study, a quantitative evaluation of GHG emissions from WWTPs can be expected and it is possible to get a closer look at the CO₂ emissions that contribute to global warming.