The work included design of 42 WWTPs from the P3-B zone of the Aragon Pyrenees area, with the necessary external connections (collector connecting to the sewerage network, outfall to receiving waterway, water supply, power supply, access and telephony). The treatment type ranged from septic tanks with filters for the smaller ones to activated sludge in prolonged aeration for the larger ones. The total population equivalent was 7,180.