Investigation of the environmental impacts of municipal wastewater treatment plants through a Life Cycle Assessment software tool

This paper investigates the total and per capita environmental impacts of municipal wastewater treatment in the function of the population equivalent (PE) with a Life Cycle Assessment (LCA) approach using the processes of the Ecoinvent 2.2 database available in the software tool SimaPro v.7.3. Besides the wastewater treatment plant (WWTP), the study also considers the sewerage system. The obtained results confirm that there is a ‘scale factor’ for the wastewater collection and treatment even in environmental terms, in addition to the well-known scale factor in terms of management costs. Thus, the more the treatment plant size is, the less the per capita environmental impacts are. However, the Ecoinvent 2.2 database does not contain information about treatment systems with a capacity lower than 30 PE. Nevertheless, worldwide there are many sparsely populated areas, where it is not convenient to realize a unique centralized WWTP. Therefore, it would be very important to conduct an LCA study in order to compare alternative on-site small-scale systems with treatment capacity of few PE.