Life cycle assessment of small-scale greywater reclamation systems combined with conventional centralized water systems for the City of Atlanta, Georgia.

Abstract This study examines a hybrid system (HS) that combines a greywater reclamation system with the centralized water system. Greywater is collected from laundry, showers, faucets and dishwashing and is reclaimed for non-potable on-site purposes (i.e., irrigation and toilet flushing) by using submerged membrane bioreactors (MBRs). This technology can reduce the burden of the conventional system (CS), defined as the water supply and wastewater treatment systems within the City of Atlanta. We conducted a life cycle assessment (LCA) comparison of the HS and CS using TRACI v2.1, which simulates ten impacts related to the ecosystem, human health and natural resources. We simulated the technology feasibility for nine residential zones, including five single-family house zones (SFZs) and four multi-family apartment building zones (MFZs) that vary by land use and population density (0.4–62.2 persons per 1000 m2). The greywater reclamation system reduces non-potable water demand in SFZs (by 17–49%) and MFZs (by 6–32%) while simultaneously reducing electricity consumption by 17–49% and 32–41% for SFZs and MFZs, respectively. Moreover, the LCA score of the CS is 20–41% lower than that of the HS. However, the sensitivity analysis indicates that energy sources in electricity generation play a critical role in reducing and stabilizing life cycle impacts. The results indicate that the LCA scores stabilize at higher population densities. Therefore, once the greywater reclamation capacity is exhausted, municipalities can further decrease the life cycle impacts related to water infrastructure through improvements in the electricity generation infrastructure.