Wastewater treatment plants (WWTPs) play an important role within the urban water cycle in protecting
receiving waters from untreated discharges. However, WWTPs processes also affect the environment.
Life cycle assessment has traditionally been used to assess the impact of direct discharges from WWTPs
and indirect emissions related to energy or chemical production. The water footprint (WF) can provide
complementary information to evaluate the impact of a WWTP regarding the use of freshwater. This
paper presents the adoption of the Water Footprint Assessment methodology to assess the consumption
of water resources in WWTPs by considering both blue and grey WFs. The usefulness of the proposed
methodology in assessing the environmental impact and the benefits from WWTP discharge to a river is
illustrated with an actual WWTP, which treats 4,000 m3
$d1
, using three scenarios: no treatment, secondary
treatment and phosphorus removal. A reduction of the water footprint by 51.5% and 72.4% was
achieved using secondary treatment and chemical phosphorus removal, respectively, to fulfill the legal
limits. These results indicate that when treating wastewater, there is a large decrease in the grey water
footprint compared with the no-treatment scenario; however, there is a small blue water footprint