Complementary life cycle assessment of wastewater treatment plants: An integrated approach to comprehensive upstream and downstream impact assessments and its extension to building-level wastewater generation

• According to the hybrid process-based/Eco-LCA life cycle method, 536,756 Mg of CO2e are emitted by the UF wastewater treatment plant in the provision of service.
• According to the hybrid process-based/EIO-LCA life cycle method, 499,036 Mg of CO2e are emitted by the UF wastewater treatment plant in the provision of service.
• Although emissions and energy use peak in the use-phase of a buildings life-cycle, the proportion of this impact that comes from the treatment of a buildings waste water is negligible.

Typical life cycle assessment (LCA) studies of Wastewater Treatment Plants (WWTP) too often focus exclusively on either upstream or downstream impacts while failing to connect this to a scale appropriate for integration in building assessments. A solution to this problem would offer a framework of tools to map the full scope of WWTP impacts, both upstream and downstream, in an integrated manner yet can be valid on an individual building level. This will allow for the capture of an aspect of the building use phase that is often neglected in the assessment process. The integrated approach discussed in this paper is unique in that it uses existing LCA methods to evaluate upstream and downstream impacts in a novel and complementary fashion. Upstream impacts are determined using three methods, namely: Economic Input–Output LCA (EIO-LCA), Ecologically-based LCA (Eco-LCA), and emergy analysis. Downstream impacts are captured through the application of U.S. Environmental Protection Agency calculations and a process-based method for land application of sludge waste products. Furthermore, this paper discusses the results that were extended to assess wastewater impacts on the scale of a specific building to complete the impact assessment from a previous study by the authors (Srinivasan et al. (2014). Building and Environment, 79, 151). The goal of this work is to develop a method to account for the upstream and downstream life cycle impacts of wastewater treatment at the plant and individual building level.