Abstract: The present invention relates to a facility (1) for treating wastewater (EM) from a building (2). This facility comprises means for collecting waste water (EM), a phyto-purification treatment module (6) which is positioned on the roof (21) of the building (2) and is configured to convert the wastewater (EM) into purified water, and means (10) for recirculating the purified water, preferably treated water (ET), in at least one interior or local circuit (B1) for the reuse of said treated water (ET) inside or in the vicinity of said building (2), and/or for discharging said treated water (ET), by default or due to an excess, into an external network (B) for sanitising or disposing of wastewater.