The purpose of the operation is the action in the sanitation and purification systems in the indicated locations to avoid inappropriate spills to the Sensitive Zone of “Albufeira Do Alqueva / Central trunk of the Guadiana River. Specifically, the sanitation and purification work to be carried out are:_x000D_ Villagonzalo: New WWTP, secondary treatment._x000D_ Torremejía: expansion and adaptation of more rigorous treatment._x000D_ La Roca de la Sierra: new WWTP, secondary treatment._x000D_ La Nava de Santiago: new WWTP, secondary treatment._x000D_ Nogales: new WWTP, secondary treatment.