Life cycle assessment of a decentralized greywater treatment alternative for non-potable reuse application

The decentralized wastewater treatment systems including collection, treatment, and recycling of treated wastewater are an efficient integrated water management solution to overcome the shortage of freshwater and to reduce pollutant emissions. In this study, life cycle assessment was performed in order to evaluate a decentralized alternative allowing the recycling of treated greywater (TGW) in a multi-family dwelling. The adopted treatment system is the moving bed biofilm reactor (MBBR). The biological treatment with MBBRs was found the main contributor to the majority of the investigated impact categories. The integration of the tertiary treatment led to an increase in the environmental load ranging between 6 and 30.4% depending on the impact category in comparison with the scenario integrating only the biological treatment. However, the final environmental profile of both scenarios presented a minor difference. Moreover, the recycling of the TGW allowed a reduction ranging between 3.9 and 17% on five impact categories compared to the no recycling scenario. It is concluded that the decentralized approach for greywater treatment and recycling is beneficial for the environment as the distribution system and the tertiary treatment didn’t increase drastically the environmental load of the plant allowing water saving. Moreover, it is recommended to use renewable energy to reduce the environmental impact associated with the energy requirement for the biological treatment which affects the global warming potential and the acidification impact categories and to substitute the polyvinylchloride pipes with polyethylene pipes to reduce emissions related to the human toxicity impact category.